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An earthquake of M = 5.6 occurred on the March 20, 2019, in Acipayam, Denizli, located in a seismically active area at the southwest Anatolian fault system, in Türkiye. It caused extensive damages of infrastructures. The relevant fault (Acipayam–Serinhisar fault zone) has not shown on the active fault map of Türkiye, and it has been discovered first time by this study. The earthquake occurred on the Acipayam segment of this fault zone, which is divided into two separate segments. Three trenches were excavated for paleoseismological studies on this segment. The samples collected from the trenches were dated by radiocarbon method. The obtained data proposed three seismic events, which caused a surface rupture, at BC 235–95, AD 1227–1263 and AD 1471–1738. Considering the last two events, this fault segment produced two earthquakes of magnitude 6.0 and 6.5, 350 years apart. [ABSTRACT FROM AUTHOR]

In this study, the active tectonics, paleoseismicity, and seismic hazards of the Doroud Fault are examined through high-resolution satellite image interpretations, field investigations, outcrop and trench excavations, and the dating of geochronology samples. The Doroud Fault (DF), one of the essential segments of the Main Recent Fault in the northern margin of the Zagros mountain range, has a historical and instrumental background of high seismicity. We present the first constraints from tectonic geomorphology and paleoseismology along the Doroud Fault near the capital city of Dorud. Detailed observations from satellite imagery, field investigations, real-time kinematic (RTK) measurements, paleoseismological trenching, the radiocarbon (C14), and optically stimulated luminescence (OSL) as ages allowed us to map the fault in detail, describe and characterize its kinematics, and document its recent activity and seismic behavior (cumulative displacements, paleoseismicity, and magnitude, as well as recurrence interval) relevant to the recent seismic activity of the Doroud Fault during the late Holocene as one of the most important seismogenic faults in Zagros. Modern alluvial terraces of gullies and loess accumulations are systematically deflected and/or offset with co-seismic rupture, landslides, and scarps, indicating that the Doroud Fault has been active in the late Quaternary and is characterized by dextral strike–slip movements with a normal component. In addition, our findings provide a comprehensive analysis of the fault displacement, the timing of paleoearthquakes, and the right-lateral slip rate of the Doroud Fault. The late Holocene slip rate of the Doroud Fault using the OSL dating the gully is as follows: the minimum and maximum horizontal slip rates are estimated to be 1.82 and 2.71 mm/yr, and vertical slip rates of 1.03 and 1.53 mm/yr are calculated for the past 4600 ± 900 years in the middle segment of the fault. This study focused on a paleoseismological trench within the archeological sites of Darbe-Astaneh. The central portion of the fault has historically hosted more than nine earthquakes in the last 66 ka years, according to the study's findings. According to paleoseismology studies, the Doroud Fault has the seismic capability to cause earthquakes with a magnitude of more than 7.4 and a total slip rate of about 3.83 ± 0.1 m. The average recurrence interval for the identified paleoearthquakes is approximately 104 ± 7 years. [ABSTRACT FROM AUTHOR]

Earthquakes occur because faults weaken with increasing slip and slip rate. Thermal pressurization (TP) of trapped pore fluids is deemed to be a widespread coseismic fault weakening mechanism. Yet, due to technical challenges, experimental evidence of TP is limited. Here, by exploiting a novel experimental configuration, we simulate seismic slip pulses (slip rate 2.0 m/s) on dolerite-built faults under pore fluid pressures up to 25 MPa. We measure transient sharp weakening, down to almost zero friction and concurrent with a spike in pore fluid pressure, which interrupts the exponential-decay slip weakening. The interpretation of mechanical and microstructural data plus numerical modeling suggests that wear and local melting processes in experimental faults generate ultra-fine materials to seal the pressurized pore water, causing transient TP spikes. Our work suggests that, with wear-induced sealing, TP may also occur in relatively permeable faults and could be quite common in nature. This paper presents experimental evidence of thermal pressurization (TP) weakening of seismic faults, and suggests TP processes could be significantly promoted by wear-induced sealing during earthquakes even for relatively permeable faults. [ABSTRACT FROM AUTHOR]

Objectives: High-precision coseismic three-dimensional (3D) deformation field is of great significance for investigating the earthquake deformation pattern and focal mechanism. For the 2021 Ms 6.4 Yang‐ bi earthquake, the characteristics of coseismic deformation observation can be described as: (1) Only two directions of interferometric synthetic aperture radar (InSAR) line of sight observations from the ascending and descending tracks; (2) lack of azimuth observation; (3) some incoherent regions existed around the epicenter; (4) sparse and unevenly distributed GNSS observation. This observational fact makes it difficult to accurately extract its coseismic 3D deformation field. Therefore, a new method is investigated to solve this issue.Methods: The new method is designed and implemented by integrating earthquake dislocation model and extended simultaneous and integrated strain tensor estimation from geodetic and satellite deformation measurements (ESISTEM) method. Firstly, the InSAR deformation field of the 2021 Ms 6.4 Yangbi earth‐ quake is obtained by using the ascending and descending Sentinel-1A/B images. Secondly, the northsouth deformation component obtained from the forward modeling of earthquake dislocation model is used as a constraint. Finally, with the new method, the complete coseismic 3D deformation field and strain field of the earthquake are successfully extracted. Results: (1) The 3D coseismic deformation field indicates that the southwest side of the Yangbi earthquake fault mainly moves westward and northward, with maxima of 4.8 cm and 9.5 cm, respectively. The northeast side mainly moves eastward and southward, with maxima of 7.4 cm and 4.6 cm, respectively. The maxima of vertical uplift and subsidence are 3.6 cm and 3.4 cm, respectively. (2) The earthquake fault is dominated by the right-lateral strike-slip movement with a small amount of normal components.(3) The strain field indicates that the earthquake fault area experiences significant expansion, shear, and rotation. Conclusions: The new method can make use of the north-south deformation component obtained from the forward modeling of earthquake dislocation model to carry out reasonable constraint, and take into account the spatial constraint between observation points. The reliability of the method is verified by the case study of the 2021 Ms 6.4 Yangbi earthquake. The method has reference value for expanding the method of extracting 3D deformation field. [ABSTRACT FROM AUTHOR]

A large earthquake unlocks a fault‐zone via dynamic rupture while releasing part of the elastic energy stored during the interseismic stage. As earthquakes occur at depth, the analyses of earthquake physics rely primarily on experimental observations and conceptual models. A common view is that the earthquake instability is necessarily related to the frictional weakening that is commonly observed in shear experiments under seismic slip velocities. However, recent experiments with frictional interfaces in brittle acrylics (e.g., Svetlizky & Fineberg, 2014, https://doi.org/10.1038/nature13202) and rocks (e.g., Passelegue et al., 2020, https://doi.org/10.1038/s41467-020-18937-0) have explicitly demonstrated that no characteristic frictional strength exists. Namely, prior to nucleation, frictional interfaces can sustain a wide range of applied stresses ("overstresses") that exceed the residual stresses, which are the stresses along the interface that remain after the sliding. Moreover, the experimentally observed singular stress‐fields and rupture dynamics are precisely those predicted by fracture mechanics (Freund, 1998). We therefore argue here that earthquake dynamics are best understood in terms of dynamic fracture mechanics and not governed by the frictional properties of faults. In this view, rupture dynamics are driven by the release of the elastic energy due to overstresses, whereas the values of the residual stresses and the energy dissipation are determined by fault frictional properties. Plain Language Summary: A large earthquake occurs when a "locked" fault becomes unlocked and starts slipping rapidly while releasing stored elastic energy. As earthquakes occur at depth, earthquake analyses rely primarily on experimental observations and conceptual models. One common view attributes the earthquake instability to the transition from the strong "static friction" to the weaker "dynamic friction." Recent observations of experimental earthquakes along brittle faults cause us to challenge this common view. These experiments have explicitly demonstrated that faults may stay locked under a wide range of imposed stress levels, thereby casting doubt on the concept of a characteristic "static friction" for a fault. Moreover, the features of these experimental earthquakes fit precisely the predictions of fracture mechanics theory (Freund, 1998). We therefore argue here that earthquake dynamics is best understood in terms of dynamic fracture mechanics, a process not directly related to the fault frictional properties. Key Points: Earthquakes as dynamic rupture phenomenaDynamic weakening by breakdown at earthquake rupture frontFracture mechanics as controlling earthquake instability regardless of frictional properties [ABSTRACT FROM AUTHOR]

Ocean transform faults often generate characteristic earthquakes that repeatedly rupture the same fault patches. The westernmost Gofar transform fault quasi‐periodically hosts ∼M6 earthquakes every ∼5 years, and microseismicity suggests that the fault is segmented into five distinct zones, including a rupture barrier zone that may have modulated the rupture of adjacent M6 earthquakes. However, the relationship between the systematic slip behavior of the Gofar fault and the fault material properties is still poorly known. Specifically, the role of pore fluids in regulating the slip of the Gofar fault is unclear. Here, we use differential travel times between nearby earthquakes to estimate the in‐situ Vp/Vs of the fault‐zone materials. We apply this technique to the dataset collected by an ocean‐bottom‐seismometer network deployed around the Gofar fault in 2008, which recorded abundant microearthquakes, and find a moderate Vp/Vs of 1.75–1.80 in the rupture barrier zone and a low Vp/Vs of 1.61–1.69 in the down‐dip edge of the 2008 M6 rupture zone. This lateral variation in Vp/Vs may be caused by both pore fluids and chemical alteration. We also find a 5%–10% increase in Vp/Vs in the barrier zone during the 9 months before the mainshock. This increase may have been caused by fluid migrations or slip transients in the barrier zone. Plain Language Summary: Oceanic transform faults are ideal natural laboratories for studying earthquake physics due to their regular behaviors. The westernmost Gofar transform fault near the East Pacific Rise generates magnitude six earthquakes every 5–6 years on two rupture zones, respectively, which are separated by a barrier zone repeatedly stopping ruptures on the adjacent segments. The distinct behavior of the barrier zone might be due to differences in material properties from the rupture zones. To explore this hypothesis, we analyze thousands of small earthquakes in 2008 and find that the barrier zone has a higher ratio between P and S velocities than the rupture zone. This difference indicates that the barrier and rupture zones differ in their fluid content and chemical composition, which may have regulated their distinct slip behaviors. We also find an increase in the ratio between P and S velocities in the barrier zone during the 9 months before the magnitude six earthquake in 2008, which may reflect fluid flows or aseismic fault slips. Our findings suggest that pore fluids and the chemical composition of fault‐zone materials likely play a crucial role in regulating the slip behaviors of oceanic transform faults. Key Points: Rupture barrier zone has a moderate Vp/Vs of 1.75–1.80Down‐dip edge of the 2008 M6 mainshock has a low Vp/Vs of 1.61–1.69Vp/Vs in the rupture barrier zone increased in the 9 months before the mainshock [ABSTRACT FROM AUTHOR]

Oceanic transform faults are intriguing in that they do not produce earthquakes as large as might be expected given their dimensions. We use 1‐year of local seismicity (370 events above MC = 2.3) recorded on an array of ocean bottom seismometers (OBSs) and geophysical data to study the seismotectonic properties of the Chain transform, located in the equatorial Mid‐Atlantic. We extend our analysis back in time by considering stronger earthquakes (MW ≥ 5.0) from global catalogs. We divide Chain into three areas (east, central, and west) based on historical event distribution, morphology, and multidimensional OBS seismicity cluster analysis. Seismic activity recorded by the OBS is the highest at the eastern area of Chain where there is a lozenge‐shaped topographic high, a negative rMBA gravity anomaly, and only a few historical MW ≥ 5.5 events. OBS seismicity rates are lower in the western and central areas. However, these areas accommodate the majority of seismic moment release, as inferred from both OBS and historical data. Higher b‐values are significantly correlated with lower rMBA and with shallower bathymetry, potentially related to thickened crust. Our results suggest high lateral heterogeneity along Chain. Patches with moderate to low OBS seismicity rates that occasionally host MW ≥ 6.0 earthquakes are interrupted by segments with abundant OBS activity but few historical events with 5.5 ≤ MW < 6.0. This segmentation is possibly due to variable fluid circulation and alteration, which may also change in time. Plain Language Summary: Oceanic transform faults (TFs) typically host earthquakes much smaller than expected based on their total seismogenic area. We study the seismotectonic properties of the Chain TF by combining 1‐year of seismicity recorded by an ocean bottom seismometer (OBS) array with geophysical data (bathymetry, tidal height, gravity anomalies). We supplement our analysis with strong historical earthquakes (M ≥ 5.0) from global catalogs. Our analysis divides Chain into three areas: The east area is characterized by the highest OBS seismicity rates, negative gravity anomalies, large topographic highs, and few historical events with 5.5 ≤ M < 6.0. The west and central areas demonstrate lower OBS seismicity rates. However, they occasionally produce M ≥ 6.0, being responsible for most of the total seismic energy release. Higher numbers of stronger events occur in areas with negative gravity anomalies and shallower water depths. Our results suggest high lateral heterogeneity along Chain, with alternating seismic and aseismic patches, variable crustal thickness, different degrees of hydrothermal circulation/alteration, and potentially time‐dependent behavior. Key Points: Segmentation along Chain transform fault (Mid‐Atlantic Ocean) is studied by means of seismicity cluster analysis and geophysical dataChain demonstrates lateral heterogeneity with high moment‐release patches interrupted by segments with abundant but small magnitude eventsSpatiotemporal variations of seismicity are possibly manifested by variable hydrothermal circulation and alteration [ABSTRACT FROM AUTHOR]

The hydrous mineral talc is stable over a relatively large P‐T field and can form due to fluid migration and metamorphic reactions in mafic and ultramafic rocks and in faults along plate boundary interfaces. Talc is known to be one of the weakest minerals, making it potentially important for the deformation dynamics and seismic characteristics of faults. However, little is known about talc's mechanical properties at high temperatures under confining pressures greater than 0.5 GPa. We present results of deformation experiments on natural talc cylinders exploring talc rheology under 0.5–1.5 GPa and 400–700°C, P‐T conditions simulating conditions at deep faults and subducted slab interface. At these pressures, the strength of talc is highly temperature‐dependent where the thermal weakening is associated with an increased tendency for localization. The strength of talc and friction coefficient inferred from Mohr circle analysis is between 0.13 at 400°C to ∼0.01 at 700°C. Strength comparison with other phyllosilicates highlights talc as the weakest mineral, a factor of ∼3–4 weaker than antigorite and a factor of ∼2 weaker than chlorite. The observed friction coefficients for talc are consistent with those inferred for subducted slabs and the San Andreas fault. We conclude that the presence of talc may explain the low strength of faults and of subducted slab interface at depths where transient slow slip events occur. Plain Language Summary: Whether faults creep by slow continuous and stable motion, generate slow slip or low‐frequency seismicity, or rupture by an unstable spontaneous event (i.e., an earthquake) is related to the mechanical properties of the minerals in place. Talc is one of the weakest minerals and is expected to form in fault interfaces. There is a lack of experimental data on the mechanical properties of talc under the pressures and temperatures that exist along deep faults and subduction zones. Here, we present results from a set of deformation experiments on talc under pressure‐temperature conditions that simulate deep faults and subducted slab interface. Results show a transition from pressure‐dependent to pressure‐independent strength at high temperatures (∼700°C). In addition, at increased temperature (≥600°C) talc shows an increased tendency for strain localization. These extremely low frictional strengths are about an order of magnitude lower than most rocks and are consistent with inferred weak interfaces along the San Andreas fault and various subducted slab interfaces at depths where creep and/or slow slip events occur. Key Points: Talc strength is pressure‐ and temperature‐dependent under conditions of deep faults and subduction zones (0.5–1.5 GPa and 400–700°C)Talc microstructure shows fracturing under all conditions tested associated with thermal weakening and increased localizationThe extremely low friction coefficient (<0.13) is consistent with the inferred strength of different subducted slab interfaces and the San Andreas fault [ABSTRACT FROM AUTHOR]

The Turkey-Syria earthquake On 6 February 2023, around 4:15 am local time, a magnitude 7.8 earthquake struck south central Turkey near the Turkey/Syria border. NASA's satellites help with earthquake response Following the magnitude 7.8 and 7.5 earthquakes that struck southern Turkey and western Syria on 6 February 2023, NASA is working to share its aerial views and data from space in ways that can aid relief and recovery workers in the region, as well as improve its ability to model and predict such events (https://www.nasa.gov/feature/nasa-s-satellites-help-with-turkey-syria-earthquake-response). Gl Similar changes were seen in the Turkish town of Gölcük after the 1999 Izmit/Kocaeli earthquake, and more recently along the coast following the 2016 Kaikoura earthquake in New Zealand - both of which were also large strike-slip earthquakes. DEC response to the Turkey-Syria earthquake A series of devastating earthquakes hit southern Turkey (now known as Türkiye) and north-west Syria in February killing over 33 000 people and injuring many more. [Extracted from the article]

On June 14, 2020, Mw 5.9 Kaynarpınar earthquake occurred in the easternmost part of the North Anatolian Fault Zone, along the Yedisu Seismic Gap near the Karlıova Triple Junction. Following the event, various agencies reported different epicenter locations. This issue and the complex fault pattern around the triple junction caused uncertainties about the ruptured fault and the rupture mechanism. To define the geometry of the ruptured fault, we (1) held a field survey within a week of the mainshock, (2) correlated our field data with the multitrack InSAR data, (3) relocated the epicenter of the mainshock, and its aftershocks, and (4) implemented moment tensor inversion analyses to the earthquakes larger than M 3.3. We defined a ~ N70E-striking surface rupture and measured the average co-seismic dextral slip magnitude as ~ 16 ± 1 cm in the field which is compatible with the horizontal displacement magnitude measured by InSAR (13–15 cm). Since no ~ N70E-striking faults were reported in the existing active fault database, we examined the prominent geomorphological structures along the rupture area. We determined two dextral fault families along the eastern part of the Yedisu Seismic Gap; (1) NW–SE-striking faults of the North Anatolian Fault Zone, and (2) N70E-striking faults forming the Kaynarpınar–Yuvaklı Fault Zone. This fault zone, defined and named in this study, is a part of the N70E-striking faults of the Turkish–Iranian High Plateau and the North Anatolian Fault Zone. The fault zone must have carried some, if not most, of the dextral sense-of-slip in the easternmost part of the North Anatolian Fault Zone during the Quaternary. [ABSTRACT FROM AUTHOR]

We summarise the geological setting of complex surface rupture of the 2016 Mw 7.8 Kaikōura earthquake in the Marlborough Tectonic Domain of New Zealand. The event was complex both seismologically and geologically but not totally dissimilar to other large historical events globally. The earthquake occurred in the comprehensively imbricated, steeply-dipping Pahau Terrane crust that exhibits numerous tectonic overprints with diverse faulting styles. The current strike slip faults of the Marlborough Fault System are immature in their structural development and occupy, at least in part, inherited faults of earlier deformation phases. Several of the faults that ruptured in 2016 may connect at seismogenic depths. A listric fault geometry is likely for many of the faults that ruptured in 2016. This interpretation is supported by crustal seismic mapping identifying listric geometries for other large faults within the region. Examination of other historic surface rupturing earthquakes in the Marlborough Tectonic Domain and globally show some complexity but not to the same level of multifault rupture as in 2016. We conclude that multifault ruptures may be enhanced in the Kaikōura region where the Australian plate crust is thinner than farther west and the plate boundary deformation, at rates of >20 mm year-1, transfers between closely-spaced faults with acute changes in surface geometry and with diverse rupture characteristics. The trend in seismic hazard assessment since 2016 is to include multifault ruptures universally, but this would be inconsistent with historic events in the Marlborough Tectonic Domain. Consideration of geological structure and history may usefully be incorporated into seismic hazard methodology to evaluate when and where multifault source models are indeed appropriate. [ABSTRACT FROM AUTHOR]

While there has been significant research on the dating of paleoearthquakes using methods such as surface cosmogenic dating, and trench-based luminescence or radiocarbon dating, this paper focuses on implementing an alternative surface dating method using a fault scarp-based optically stimulated luminescence (OSL) dating approach. Hence for the first time, we investigated the Pleistocene to Holocene earthquake cycle of the Manisa Fault, one of the dip-slip active faults of the Western Anatolia extensional province, utilizing novel OSL surface exposure techniques. In this technique, OSL bleaching profiles on the fault surface are directly related to the exposure of the fresh fault scarps that are produced by earthquakes. The results indicate that the Manisa Fault is responsible for at least six surface rupturing earthquakes since the Holocene, occurring at 154 ± 22 year (E6: LSD3), 416 ± 48 year (E5: LSD4), 1103 ± 82 year (E4: LSD5), 2067 ± 138 year (E3: LSD6), 5376 ± 48 year (E2: LSD7), and 6432 ± 218 year (E1: LSD8). Our results of the first use of this novel method on the Manisa Fault are in agreement with prior cosmogenic dating of fault scarps and trench-based paleoseismological chronological data, and we conclude that the OSL surface chronology is a promising alternative for fault scarp dating of paleoearthquakes. [ABSTRACT FROM AUTHOR]

We consider a model for elastic dislocations in geophysics. We model a portion of the Earth's crust as a bounded, inhomogeneous elastic body with a buried fault surface, along which slip occurs. We prove well-posedness of the resulting mixed-boundary-value-transmission problem, assuming only bounded elastic moduli. We establish uniqueness in the inverse problem of determining the fault surface and the slip from a unique measurement of the displacement on an open patch at the surface, assuming in addition that the Earth's crust is an isotropic, layered medium with Lamé coefficients piecewise Lipschitz on a known partition and that the fault surface satisfies certain geometric conditions. These results substantially extend those of the authors in [Arch. Ration. Mech. Anal. 263, 71-111 (2020)]. [ABSTRACT FROM AUTHOR]

An earthquake (magnitude, ML = 3.8) occurred on 31 October 2019 at 11:19 hours Greenwich Mean Time (GMT) in the Sunduza area of the KwaZulu-Natal (KZN) Province in South Africa. The earthquake was located near the broad fracture zone of the Ntlakwe-Bongwan fault and was felt along the eastern coast of South Africa. The effects of the event were assessed by conducting macroseismic investigations through interviewing members of the public and completing questionnaires. Analysis of all the collected macroseismic data showed that maximum shaking with Modified Mercalli Intensity of IV-V and V were experienced near the epicentral area as well as along the coast. Similar intensity values were also experienced in some parts of Durban about 100 km northeast of the epicentre. Shaking at such long distances was attributed to ground motion amplification due to site effects. A fault plane solution of the event obtained using both the first motion polarities and amplitude ratios showed normal faulting along a fault oriented in a strike of 185.0°, dipping at 68.0° with a rake of -52.0°. The strike of the focal mechanism solution aligns with the strike of the Ntlakwe-Bongwan fault zone and nearby faults suggesting that the event might have ruptured along one of the fracture segments of this fault mapped to the north. The obtained dip is also in line with a high angle fault comparable to that observed along the Ntlakwe-Bongwan fault. The epicentral region is highly faulted although the activity is not known. [ABSTRACT FROM AUTHOR]

The fracture characterization using a geostatistical tool with conditioning data is a computationally efficient tool for subsurface flow and transport applications. The main objective of the paper is to propose a framework of the geostatistical methods to model the fracture network. In the method, we have chosen a neighborhood area to apply the Gaussian Sequential Simulation in order to generate the fracture network in the unknown region. The angle was propagated from the seed where the neighborhood data guide direction. The Poisson procedure is used to distribute initial seeds. The method is applied for geological faults from Central Kazakhstan and for field data from Scotland, UK. The simulation results are compatible with the original fracture network in the flow and transport modeling setting. From the research that has been carried out, it is possible to conclude that the numerical simulation of fracture network is a valuable tool in subsurface flow and transport applications. [ABSTRACT FROM AUTHOR]

The geomorphic expression of active faulting and distinction of paleoseismic events in areas that are rapidly obscured by erosion/sedimentation still remains a considerable scientific problem. The present article discusses the revealing of surface faulting ruptures and their parameters to identify capable faults without trenching and to estimate the magnitude of earthquakes. The case study was at Cape Rytyi, located in Baikal-Lena Nature Reserve on the northwestern shore of Lake Baikal. Based on unmanned aerial photography, GPR, and structural observations, we mapped and investigated the relation between geomorphological forms and ruptures. The obtained results show that past landslides and paleoruptures at Cape Rytyi and its surroundings are associated with at least two earthquakes. The Mw of the earlier event was 7.3 (Ms = 7.4); the Mw of the later one was 7.1 (Ms = 7.3). The paleoruptures in the distal part of the delta of the Rita River and on the southeastern slope of the Baikal Ridge were included in the seismogenic rupture zone, which traces some 37 km along the Kocherikovsky fault. The approximate intervals in which earthquakes occurred are 12–5 ka and 4–0.3 ka, respectively. The applied analysis methods can be useful for paleoseismology and assessing seismic hazards in similar regions elsewhere. [ABSTRACT FROM AUTHOR]

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Sensor faults have been observed to negatively impact the operation of the HVAC system. Among these faults is the complexity of multi-source sensor faults, which may result in fault confusion due to multiple fault points and different fault patterns. This paper proposes a fault diagnosis model applicable to single- and multi-source faults of HVAC system sensors. Based on the distribution patterns of chillers sensor data, the ensemble empirical mode decomposition soft threshold denoising Gaussian mixture model (EEMDSTD-GMM) is proposed. The study suggests a K-means-based pre-classification method for potentially confusing types of sensor faults. EEMDSTD-GMM-K-means has shown a better fault diagnosis capability under four single-source sensor faults and five multi-source sensor faults. Under the three examined fault levels, the results indicate a satisfactory performance with an average diagnosis rate of 98.7% for single-source faults and 96.5% for multi-source faults. [ABSTRACT FROM AUTHOR]

Microseismicity associated with fluid pressurization in the subsurface occurs during fluid injection but can also be triggered after injection shut‐in. Understanding the extent and duration of the post‐injection microseismicity is critical to limit the risk of fluid‐induced seismicity and insure the safe utilization of the subsurface. Using theoretical and numerical techniques, we investigated how aseismic slip on a fault plane evolves and stops after a fluid pressurization event. We found that the locking mechanisms controlling the arrest of aseismic slip highly depend on the initial fault stress criticality and the pressurization duration. The absolute arrest time of fault aseismic slip after injection shut‐in is proportional to the pressurization duration and increases significantly with the initial fault stress criticality. Given that microseismicity can be triggered by aseismic slip, these results provide insights into the mechanics controlling the arrest of microseismicity after fluid pressurization as a milestone toward induced seismicity mitigation strategies. Plain Language Summary: Injection of fluid in the subsurface for energy and storage applications can lead to the onset of microseismicity, and possibly to major induced seismic events. Fluid pressurization decreases the shear strength of surrounding faults and slip occurs when the in situ shear stress on a fault reaches its shear strength. The nature of slip (aseismic or seismic) depends on the rate at which it occurs and thus on the stability of the deformation. Understanding the mechanics controlling the onset and arrest of aseismic slip and the transition to seismic slip is therefore key to design mitigation strategies for the safe utilization of the subsurface. In this contribution, we investigate using theoretical and numerical techniques how aseismic slip on a fault plane nucleates and evolves in response to fluid injection and how it stops after injection shut‐in when fluid pressure relaxes. We demonstrate that critically stressed faults prior to injection can slip for a longer time after injection shut‐in than during injection and that the extent of rupture can double in size after the end of injection. These results help to quantify the duration and sphere of influence of fluid injection where microseismicity can occur during and after injection. Key Points: Quantification of fault aseismic slip that continues to propagate away from the former injection point after injection shut‐inArrest time of aseismic slip is proportional to the pressurization durationCritically stressed faults slip significantly longer and at a greater distance than marginally pressurized faults after injection shut‐in [ABSTRACT FROM AUTHOR]

Large gas reserves have been found in the Permian platform margin of the Kaijiang-Liangping area of the Sichuan Basin in SW China. They are assumed to be a widely developed reef–shoal reservoir. However, the tight matrix reservoir cannot support high gas production using conventional development technology at deep subsurface. In this contribution, we analyze the fractured reservoirs along the strike-slip fault zones using the compiled data of cores, well logging, and production data, and provide a seismic description. It was shown that the fractures and their dissolution developed along the strike-slip fault zones. The porosity and permeability of the fractured reservoir could increase by more than one and 1–2 orders of magnitude, respectively. The seismic anisotropic energy found in the steerable pyramid process suggests that fractured reservoirs have a strong heterogeneity, with a localized fault damage zone. This fracturing has both positive and negative effects, showing varied reservoir parameters in the fault damage zone. The development pattern should adopt a non-uniform well pattern, in order to target the localized "sweet spot" of the fractures in these deep tight matrix reservoirs. [ABSTRACT FROM AUTHOR]

Precise earthquake locations and InSAR (Interferometric Synthetic Aperture Radar) deformation observation are the major methods to understand the earthquake occurrence and disaster-causing process. This paper proposes a processing framework for analyzing strong earthquake mechanisms from one-dimensional velocity inversion to precise earthquake locations combined with InSAR deformation observation, and discusses earthquake-generating fault and dynamic mechanisms of tectonic deformation. We analyzed the Menyuan Ms 6.9 earthquake in 2022 and discuss the historical seismic activities and corresponding stress adjustment processes in the research region. To analyze and study the seismogenic structure and mechanism of the earthquake, we investigated the spatial and temporal distribution characteristics of the Menyuan earthquake sequence and analyzed the InSAR coseismic deformation field. We obtained the precise locations of the main shock and aftershocks and the coseismic InSAR deformation field of the main shock. It was confirmed that the Ms 6.9 earthquake was a shallow sinistral strike-slip earthquake, which led to the sequential activation of the Tuolaishan and Lenglongling faults. The main seismogenic fault of the mainshock was the northwestern end of the Lenglongling fault, and the earthquake rupture was segmented. It can be inferred that the earthquake was a stress-adjusted event triggered in the Qilian-Haiyuan tectonic belt caused by the northeasterly push of the Qinghai-Tibet Plateau. The risk of moderate to high earthquakes in the region remains high in the future, requiring enhanced seismic observations. [ABSTRACT FROM AUTHOR]

The 2021 Mw 7.4 Maduo (Madoi) earthquake that struck the northern Tibetan Plateau resulted in widespread coseismic deformation features, such as surface ruptures and soil liquefaction. By utilizing the unmanned aerial vehicle (UAV) photogrammetry technology, we accurately recognize and map 39,286 liquefaction sites within a 1.5 km wide zone along the coseismic surface rupture. We then systematically analyze the coseismic liquefaction distribution characteristics and the possible influencing factors. The coseismic liquefaction density remains on a higher level within 250 m from the surface rupture and decreases in a power law with the increasing distance. The amplification of the seismic waves in the vicinity of the rupture zone enhances the liquefaction effects near it. More than 90% of coseismic liquefaction occurs in the peak ground acceleration (PGA) > 0.50 g, and the liquefaction density is significantly higher in the region with seismic intensity > VIII. Combined with the sedimentary distribution along-strike of the surface rupture, the mapped liquefaction sites indicate that the differences in the sedimentary environments could cause more intense liquefaction on the western side of the epicenter, where loose Quaternary deposits are widely spread. The stronger coseismic liquefaction sites correspond to the Eling Lake section, the Yellow River floodplain, and the Heihe River floodplain, where the soil is mostly saturated with loose fine-grained sand and the groundwater level is high. Our results show that the massive liquefaction caused by the strong ground shaking during the Maduo (Madoi) earthquake was distributed as the specific local sedimentary environment and the groundwater level changed. [ABSTRACT FROM AUTHOR]

To ensure the safety operation of inter-basin water transfer project, it is important to understand the seismic performance of shallow-buried large-scale segment-connected pipeline structure under earthquake and other multiple actions. In this paper, a 3D FE model is built in details for the seismic assessment of large-scale prestressed concrete inverted-siphon shallow-buried under riverbed, and a method is proposed to realize multiple interactions of the viscoelastic boundary elements to finite elements, the compressible fluid to structure and the sealed joints made of rubber belt between adjacent segments. The inverted-siphon is longitudinally composited by 58 segments in total length of 858.64 m, and transversally consisits of three rectanguler-section boxes with net dimension of each box of 6.5 m width and 6.6 m height. The main influencing factors are set as the thickness of overburden soil, the flow condition and the engineering geological condition. The time-history analysis is carried out on the 3D FE model under Elcentro seismic wave excitation. The numerical analyses figures out the main vibration modes and vibrational frequency of this inverted-siphon, reveals the regions of peak tensile stress appeared on the concrete surface and the risk sealed joints with extremum relative displacement. This provides a scientific reference to take specific prevention measures of anti-earthquake, based on a deep understanding to the seismic cracking of concrete and the tearing broken of sealed joints for this kind of segment-connected pipeline structure. [ABSTRACT FROM AUTHOR]

The anatomical characteristics (fiber length and fiber area) and mechanical properties (modulus of elasticity, modulus of rupture, compressive strength, tensile Young's modulus, and tensile strength) of Bambusa vulgaris, Bambusa maculata, and Gigantochloa atter, naturally growing at four different sites in Lombok Island, Indonesia, were examined for evaluating geographic and longitudinal variations by mixed-effects modeling to effectively utilize bamboo culm resources for structural materials. We found geographic and longitudinal variations of bamboo culm properties in these three species. Based on the results, we concluded that, for utilization of bamboo culm as a structural material, variation of individual culm rather than site, and longitudinal variations should be considered for Bambusa species and G. atter, respectively. [ABSTRACT FROM AUTHOR]

We use ocean bottom seismometer data from the Endeavour segment of the Juan de Fuca ridge to construct a long‐term earthquake catalog for an intermediate spreading rate mid‐ocean ridge. We present >50,000 new earthquake locations for 2016–2021 from the Ocean Networks Canada NEPTUNE cabled observatory and relocate earthquakes from two autonomous networks in 1995 and 2003–2006. The catalog comprises >85,000 earthquakes located using three‐dimensional segment‐scale P and S wave velocity models from a prior tomography experiment. Despite the small footprints of networks near the segment center, locations show good agreement with geologic features at segment ends. The improved locations show that the northern Endeavour segment ruptured southwards from 48.3°N to 48.05°N during two diking events in early 2005, possibly accompanied by diking on the West Valley (WV) propagator. Persistent off‐axis seismicity near the segment center appears to be related to the WV and Cobb propagating rifts which we infer extend ∼10 km closer to the Endeavour segment center than is apparent in bathymetry. We suggest that the proximity of the propagators to the Endeavour vent fields (VFs) contributes to the localization, vigor, and longevity of the fields by focusing permeability through ongoing fracturing and by limiting extrusive magmatism through degassing of the axial magma lens. Increasing rates of seismicity beneath the VFs beginning in late 2018 and a deepening of earthquakes in 2020 indicate that the central portion of the segment may be entering the later stages of the eruptive cycle. Plain Language Summary: Seafloor spreading centers are boundaries where tectonic plates move apart and ocean crust is created by volcanism. Small earthquakes in these settings result from extensional faulting, magma injection, and cooling of the crust by circulating fluids. Seafloor spreading is cyclical: strain steadily builds up as the plates move apart and is relieved episodically when magma is injected into the crust. Earthquake activity must be observed on the order of decades to fully capture this cycle. Until recently, however, batteries have limited earthquake observations from autonomous seafloor seismometers to about a year. We combine observations from a new long‐term undersea cabled observatory and older experiments to present an earthquake catalog that spans 20 years for the Endeavour segment of the Juan de Fuca ridge. We improve earthquake locations relative to past studies and relate evolving earthquake activity to seafloor features. Our results suggest that the complicated geometry of nearby plate boundaries, through focused fracture creation, affects how fluids circulate through the crust. Earthquake patterns preceding the last observed magmatic event in 2005 indicate that the increases in earthquake rates and depths we observe in 2018–2020 may be signs of the center of the segment nearing the next spreading event. Key Points: Three‐dimensional velocity models facilitate reliable earthquake localization in the marine setting despite limited seismometer coveragePropagating rift tectonics enable long‐lived high‐temperature hydrothermal venting through amplified and spatially focused deformationEarthquakes across 20 years reflect strain that evolves cyclically as extension is accumulated and released on overlapping spreading axes [ABSTRACT FROM AUTHOR]

Key factors controlling earthquake ruptures include fault geometry, continuity, and seismic velocity structure around the fault. We present a novel tool that better informs deep bimaterial fault geometry embedded in distributed damage and seismicity, associated velocity contrasts across the fault, and their correlations with surface complexities. The method employs fault zone head and direct body waves and is applied to recordings from five spatiotemporally different seismic arrays along the complex San Jacinto fault zone (SJFZ) in southern California. We detect and distinguish these signals based on instantaneous phase coherence and relative energy in a cascading manner from one scale array to another. The analysis reveals a >70‐km long continuous bimaterial interface within the SJFZ with several deep northeast dipping fault segments. The northern SJFZ, for instance, locates ∼7 km northeast of its surface expression at 18‐km depth. P‐wave velocity contrasts range from near 0% to >15%, consistent with other bimaterial faults, and differ by a few % depending on fault‐array azimuth, implying directional‐dependent velocity contrasts. S‐wave head waves and velocity contrasts are also imaged for the first time at the southern SJFZ, averaging to 2.9% in agreement with tomography results. The imaged geometry and continuity suggest the SJFZ initiated along remnant tectonic structures and translates to a rupture potential of M > 7.2, i.e., the sizes of its largest paleo‐earthquakes. The P and S contrasts, and their ratios, have important implications for earthquake rupture speed, mode, directivity, and frictional heating along the SJFZ and other major faults globally. Plain Language Summary: Large earthquakes occur on faults that are structurally complex, leading to earthquakes that are themselves structurally and dynamically complex. More accurate information on fault complexities is key to quantifying the potential size and shaking from large earthquakes along them. Here, we introduce a novel tool that resolves the deep geometry, continuity, and contrast in seismic velocity along major transform fault systems using the complex San Jacinto fault zone (SJFZ) in southern California as an exemplary case. It employs unique signals that travel along, and illuminate, continuous faults contrasting rock volumes of different seismic properties. With this tool, we reveal a >70‐km long continuous fault within the SJFZ that is nonsimple and nonplanar, curving laterally, and in depth. For example, a deep northern section of the SJFZ dips extensively toward the northeast. The seismic velocity contrast across the entire fault varies from 0% to >15% and depends on the angle of observation from the surface. This long continuous fault is capable of an M > 7.2 earthquake and likely initiated along older structures that predate the SJFZ. The observed geometries and velocity contrasts have implications for the direction, speed, distribution, and other key defining features of large SJFZ earthquakes. Key Points: Image the San Jacinto fault zone with direct body and fault zone head waves recorded by several dense arrays along the faultReveal a ∼72‐km long continuous bimaterial interface within the core fault zone with variable geometry and P‐ and S‐wave velocity contrastsEstimated bimaterial properties have important implications for earthquake rupture properties along the San Jacinto and other faults [ABSTRACT FROM AUTHOR]

Repeating earthquakes, or repeaters, which repeatedly rupture the same location and release the strain energy, are interpreted as repeated ruptures of an isolated asperity patch surrounded by a stable sliding regime. While repeaters are frequently observed along plate‐boundary faults, the occurrence of repeater sequences are reported in various tectonic settings. Here we systematically investigate whether repeaters occur in the continental crust and subducting slabs beneath the Japanese Islands and show a prevalence of repeaters in both locations. The crustal and intraslab repeaters show the power‐law decay of seismicity rates that is identical to that along plate‐boundary faults and occur on well‐defined fault planes coincidentally with non‐repeating earthquakes. These observations suggest that repeaters share a common generation process independent of the tectonics regime and are not distinct from non‐repeaters in their source locations and occurrence times. We thus infer that repeaters and non‐repeaters are both generated by ruptures of locked asperities in response to stress loading by aseismic slip in the surrounding stable regime. Repeater sequences can be observed when aseismic slip is large enough to rupture an isolated asperity more than twice, while no repeaters are generated when the amount of aseismic slip is not sufficient to cause multiple ruptures at an isolated asperity. Since an earthquake cannot be triggered unless the amount of the aseismic stress loading exceeds the strength of asperities at the fault, hidden aseismic slip probably occurs repeatedly and frequently during an interseismic period. Plain Language Summary: The majority of earthquakes occur at three places in the Earth; along plate boundaries where two plates are adjacent, in downgoing plates (slabs), and in continental plates. However, whether the same generation mechanism works for the earthquakes in the different tectonic regimes is still debatable. Earthquakes with very similar waveforms have been recognized since ∼1900, and we recognize at present that many of such similar earthquakes are repeating earthquakes, or repeaters. The repeaters are caused by repeated ruptures of an isolated, frictionally locked asperity patch by stress loading due to aseismic slip in the surrounding stable regime. This study reveals that these repeaters occur prevalently in both the continental crust and slabs beneath the Japanese Islands. We find that there are no substantial differences in the hypocenter locations and occurrence time between repeaters and non‐repeaters. These observations suggest that all earthquakes share a common generation mechanism. We hypothesize that aseismic slip plays an essential role in stress loading to frictionally locked areas and an earthquake occur when the amount of aseismic slip exceeds the strength of faults. Our idea, although it needs further verification, will help better understanding of how frequent aseismic slip occurs and how earthquakes are triggered. Key Points: Repeating earthquakes are more common in the continental crust and subducting slabs than previously consideredRepeaters are not distinct from non‐repeaters in their source locations and occurrence timesRepeaters and non‐repeaters are triggered by ruptures of locked asperities by stress loading of aseismic slip [ABSTRACT FROM AUTHOR]

The strength and sliding behavior of faults in the crust is largely controlled by friction and effective stress, which is itself modulated by fluid pressure. Most earthquake models assume a fixed pore fluid pressure despite widespread evidence that is varies strongly in time due to changes in permeability. Here we explore how dynamic changes in pore pressure influence the properties of earthquakes in the upper crust. To study this problem we develop a two dimensional model that incorporates slow tectonic loading and fluid pressure generation during the interseismic period with frictional sliding on a thrust fault whose permeability evolves with slip. We find that the presence of relatively modest fluid overpressures tends to reduce coseismic slip, stress drop, maximum sliding velocity, rupture velocity and the earthquake recurrence time compared to models without fluids. Our model produces a wide range of sliding velocities from rapid to slow earthquakes, which occur due to the presence of high pore pressures prior to rupture. The models also show evidence for aftershocks that are driven by fluid transfer along the fault plane after the mainshock. Overall, this study shows that fluids can exert an important influence on earthquakes in the crust, which is mostly due to modulation of the effective stress and variations in permeability, and to a lesser extent to poro‐elastic coupling. Plain Language Summary: In this study we use a numerical model to investigate how fluid pressures vary over the seismic cycle and how they interact with and influence the properties of earthquakes that occur in the upper crust. In the model, fluid overpressures are generated slowly during the interseismic period by phenomena such as dehydration reactions while they are episodically released during earthquakes due to fracturing and a dramatic increase in permeability. The models show that the presence of high fluid pressures has an important influence on earthquakes. High fluid pressures favor smaller, more frequent earthquakes. Also high fluid pressures may sometimes be responsible for aftershocks and for anomalously slow earthquakes that involve slip over several months rather than several seconds. Overall, we show that the presence of fluids in the crust plays an integral part in the earthquake process. Key Points: Properties of earthquakes are markedly influenced by the presence of fluid overpressuresRuptures in wet models have relatively low stress drops, sliding speed and rupture velocitySlow slip events and aftershocks might be a fingerprint of fluid overpressures [ABSTRACT FROM AUTHOR]

A variety of mechanisms have been proposed to explain how a fault might deform relatively slowly, rather than manifesting as earthquakes. Several rely on the frictional properties of the fault interface. In this study I analyze the slip stability of a fluid‐infiltrated fault in the framework of a microphysically‐based friction model, which has shear zone porosity as its state variable. Linear stability analysis of the model, incorporating the evolution of fluid pressure, gives the critical stiffness (kc ${k}_{c}$) and frequency (wc ${w}_{c}$) as a function of normalized dilatancy (E/Ec $E/{E}_{c}$) and diffusivity (U $U$) factors. The theoretical results are similar to those derived from the previous friction laws, except that a positive kc ${k}_{c}$ always exists, even for a highly‐dilatant, impermeable fault where the value is proportional to the diffusivity. This implies that dilatant faults in impermeable media are potentially seismogenic, while the previous models predict negative kc ${k}_{c}$, implying a stable fault regardless of loading stiffness (k). Adopting a spring‐slider fault analogue, the analytical results are verified numerically under a wide span of spring stiffness, dilatancy, and diffusivity factors. The numerical results further reveal that four different modes of periodic slow slips can emerge in the model, without invoking inertia, which is distinct from previous friction models. Translating kc ${k}_{c}$ into the scenario of an elastically‐deformable medium, the critical wavelength on a dilatant fault can be as long as tens of kilometers. Gaining insights from all these features, I posit that the microphysical model is inherently favorable for generating slow slips. Plain Language Summary: As stress accumulates, a frictional interface can move either suddenly or slowly. The same phenomenon also occurs in natural fault zones. Until very recently, the slow motion of the fault interface (so‐called "slow slips") was observed in the subduction zones such as those in Japan. For the purpose of modeling these slow fault motion processes, a useful result would be a physically‐based constitutive relation that well characterizes the relevant observations and underlying mechanisms. This study analyzes the motion behavior of a fluid‐infiltrated fault zone in the framework of a microphysically‐based friction model, that is, slow and continuous sliding versus episodic acceleration of slip, like earthquakes. Interestingly, four mechanisms that have been previously proposed and widely used in the simulations to damp an accelerated fault emerge naturally from the analyzed model. The theoretical analysis further tells that the microphysical model is inherently favorable for the generation of slow fault slips. Key Points: Various damping regimes emerge as slip accelerates in a fluid‐infiltrated faultEven highly dilatant and low‐permeability faults are potentially unstableFour distinct types of slow slip events are predicted by the microphysical friction model [ABSTRACT FROM AUTHOR]

Rock joints in faulted zones are usually filled with large amounts of fault gouge, in which clay-rich fillings are very common. Fault water can significantly influence the mechanical parameters of clay-rich fillings and affect the shear mechanical behaviour of rock joints. Based on a tunnelling project passing through a faulted zone in Yunnan Province of China, this paper investigates the mechanical behaviour of rock joints with clay-rich fillings. A series of direct shear tests are conducted on rock joint samples made from rock blocks and fillings collected from a fault zone. The shear stress‒displacement curves and shear failure characteristics of rock joints are obtained, and several key factors of the fillings are considered, such as particle size, mineral composition, clay content, and water content. Furthermore, the peak and residual shear strengths are analysed by considering the influence of the water content and normal loading pressure. The test results show that water content of fillings has a great influence on shear strength of clay-filling rock joints; there is a trend to a negative correlation between the shear strength of rock joints when water content (w) exceeds the plastic limit (wp). Finally, a shear strength model for rock joints with clay-rich fillings is proposed based on the JRC-JCS strength criterion. Influence of water content on the shear strength of rock joints with clay-rich fillings is studied. A series of direct shear tests are conducted on rock joint samples based on a tunnelling project. The shear stress–displacement curves of rock joints with clay-rich filling are obtained. A shear strength weakening model of clay-filled joints is proposed. Highlights: Influence of water content on the shear strength of rock joints with clay-rich fillings is studied. A series of direct shear tests are conducted on rock joint samples based on a tunnelling project. The shear stress-displacement curves of rock joints with clay-rich filling are obtained. A shear strength weakening model of clay-filled joints is proposed. [ABSTRACT FROM AUTHOR]

We obtain explicit estimates on the stability of the unique continuation for a linear system of hyperbolic equations. In particular, our result applies to the elasticity system and also the Maxwell system. As an application, we study the kinematic inverse rupture problem of determining the jump in displacement and the friction force at the rupture surface, and we obtain new features on the stable unique continuation up to the rupture surface. [ABSTRACT FROM AUTHOR]

The 2010 Beni-Ilmane earthquake sequence, with 3 Mw ≥ 5.2 mainshocks, occurred in the southern Tellian Atlas approximately 200 km southeast of the Algiers. We offer updated 3D Vp and Vs models, and we outline the space and time variations in the Vp/Vs ratio of the Beni-Ilmane crust based on 2297 well-located aftershocks representing the complete aftershock sequence. Two main P-wave low-velocity patterns correspond to fault alignments determined from geological studies: the NE–SW thrust fault located at the foot of Djebel Choukchot and the NNW–SSE oriented Samma strike-slip corridor. The former crosscuts the two P-wave high-velocity anomalies of the Kef Ouagnane and Kef Kherrat summits of the Choukchot Mountains. The third high-velocity anomaly represents the Jebel Affroun Mountain in the sub-Bibanic domain. Two high-Vp/Vs ratio patterns were revealed in the central aftershock part and along the NE–SW Ouanougha syncline, which constitutes a fluid reservoir and a fluid-saturated fault zone filled after aftershock activity. The 4D Vp/Vs models monitored fluid migration, and the modeled pore-pressure diffusion revealed that earthquake rupture along an ~ N–S blind strike-slip fault fractured the closed reservoir and released high-pressure fluids, provoking a notable and long-lasting aftershock sequence. Our study underlines that local earthquake tomography (LET) can provide useful insights into the upward migration of fluids from a compartmentalized hydrocarbon reservoir. [ABSTRACT FROM AUTHOR]

This paper presents a case study of deep excavation adjacent to an existing bridge in karst region of Guangzhou city, China. The movements of retaining structures, settlements of surrounding ground and pipelines, and the responses of bridge piles were measured and evaluated. A sudden surge of groundwater was recorded at the north pit when excavated halfway. Soil-cement columns using the Metro Jet System (MJS) method was employed along the outer perimeters of the diaphragm wall where water inflow occurred, for the sake of blocking the flow channels. The measured maximum wall deflection dhm in this case ranged from 0.13 %H to 0.3 %H, with a mean value of 0.2 %H (H is the excavation depth), which agreed well with the empirical prediction in mixed ground. During the MJS treatment, the wall and surrounding soils experienced notable lateral deflection and settlement. The bridge piles experienced significant settlement since the excavation commenced, which might be attributed to the inherent deficiency in geological condition and pile length. The soil disturbance induced by the adjacent deep excavation accelerated bridge settlement. The finite element analysis revealed that the excessive settlement of the bridge piles and ground surface resulted from confined-water withdrawal in sand layers. [ABSTRACT FROM AUTHOR]

The northeastern Tibetan Plateau (TP) is one of the best places to investigate the growth mechanism of the Tibetan Plateau due to its dramatic deformation. We calculate regional gravity changes and 3-D crustal deformations based on geodetic datasets, such as campaign gravity, GPS, and leveling observations. Obvious negative–positive gravity changing signals appear in both sides of the Qilian-Haiyuan fault, which indicate material accumulation and reduction, respectively. We therefore suggest that the northeastern TP thrust towards the North China Craton (NCC) is due to the northward advance of Tibetan Plateau. The crustal movement velocity decreases stepwise from south to north, which is bounded by the thrust or strike-slip faults, and varies from 15.4 ± 0.1 mm/year in the Songpan-Ganzi block to 4.7 ± 0.02 mm/year in the Alax block. The tectonic uplift rate from leveling observations, with surface loads and glacier isostatic adjustment (GIA) deformation corrected, show the fastest uplift zone occurring in the south Liupan Shan fault and West Qinling fault, with a rate of approximately 4.3 ± 0.1 mm/year. In addition, we compare the material movement rate between the upper crust and mid-lower crust, and the results reveal that material movement in the mid-lower crust is faster than that in the upper crust, which may suggest the existence of a mid-lower crustal flow beneath the West Qinling block. We propose a geodynamic and kinematic model to quantitatively interpret the crustal deformations in the northeastern TP, which is helpful for further understanding the growth mechanism of the northeastern TP. [ABSTRACT FROM AUTHOR]

On rocky tectonic coasts, data from Holocene marine terraces may constrain the timing of coseismic uplift and help identify the causative faults. Challenges in marine terrace investigations include: (1) identifying the uplift datums; (2) obtaining ages that tightly constrain the timing of uplift; (3) distinguishing tsunami deposits from beach deposits on terraces; and (4) identifying missing terraces and hence earthquakes. We address some of these challenges through comparing modern beach sediments and radiocarbon ages with those from a trench excavated across three terraces at Aramoana, central Hikurangi Subduction Margin, New Zealand. Sedimentary analyses identified beach and dune deposits on terraces but could not differentiate specific environments within them. Modern beach shells yielded modern radiocarbon ages, regardless of position or species, showing age inheritance and habitat is likely not an issue when dating shells on these terraces. By integrating terrace mapping, stratigraphy, morphology, and radiocarbon ages we develop a conceptual model of coastal uplift and terrace formation following at least two, possibly three, earthquakes at 5490–5070, 2620–2180, and 950–650 cal. yr bp. A high step and time gap between the upper two terraces raises the possibility that at least one intervening terrace is completely eroded. The trench exposure also showed that terrace stratigraphy may differ from that inferred from surface geomorphology, with apparent beach ridges being of composite origin and draping of younger beach deposits on the outer edge of a previous terrace. Dislocation modelling and comparison of marine terrace and earthquake ages from ~4 km south and ≤ 73 km north confirms that the most likely earthquake source is the nearshore, landward‐dipping, Kairakau Fault. Alternative sources, such as multi‐fault ruptures of the Kairakau‐Waimārama faults or Hikurangi subduction earthquakes, and/or a combination of the two are also possible and should be examined in future studies. [ABSTRACT FROM AUTHOR]

We provide high‐resolution seismic imaging of the central Garlock fault using data recorded by two dense seismic arrays that cross the Ridgecrest rupture zone (B4) and the Garlock fault (A5). Analyses of fault zone head waves and P‐wave delay times at array A5 show that the Garlock fault is a sharp bimaterial interface with P waves traveling ∼5% faster in the northern crustal block. The across‐fault velocity contrast agrees with regional tomography models and generates clear P‐wave reflections in waveforms recorded by array B4. Kirchhoff migration of the reflected waves indicates a near‐vertical fault between 2 and 6 km depth. The P‐wave delay times imply a ∼300‐m‐wide transition zone near the Garlock fault surface trace beneath array A5, offset to the side with faster velocities. The results provide important constraints for derivations of earthquake properties, simulations of ruptures and ground motion, and future imaging studies associated with the Garlock fault. Plain Language Summary: Along the northern edge of the Mojave Desert, the Garlock fault intersects the San Andreas fault and is the second largest (∼300 km long) fault in Southern California. It can host M > 7 earthquakes that pose significant seismic hazard to densely populated communities. However, the subsurface structure of the Garlock fault is not well understood due to the sparse seismic network and lack of seismic activity nearby. The 2019 Ridgecrest earthquake sequence in the Eastern California Shear Zone led to a rapid deployment of several dense linear arrays with ∼100 m spacing and apertures of a few kilometers, which cross the Ridgecrest rupture zone and also the Garlock fault. The recorded seismic data is used here to illuminate the internal structure of the central Garlock fault. Analyses of P‐wave delay times and waves refracted along and reflected by the fault interface indicate a near‐vertical Garlock fault that separates two distinctive crustal blocks with different wave speeds. The resolved high‐resolution fault zone image can have important implications for multiple studies associated with the Garlock fault. Key Points: We image the central Garlock fault using data of aftershocks of the 2019 Ridgecrest earthquake recorded by two dense linear arraysA P‐wave velocity contrast across the fault (∼5% faster in the north) generates clear fault zone head and reflected wavesKirchhoff migration of P waves reflected by the fault indicates a near‐vertical interface with a sharp impedance contrast [ABSTRACT FROM AUTHOR]

The intensity and damage potential of earthquakes are linked to the speed at which rupture propagates along sliding crustal faults. Most earthquakes are sub-Rayleigh, with ruptures that are slower than the surface Rayleigh waves. In supershear earthquakes, ruptures are faster than the shear waves, leading to sharp pressure concentrations and larger intensities compared with the more common sub-Rayleigh ones. Despite significant theoretical and experimental advances over the past two decades, the geological and geomechanical controls on rupture speed transitions remain poorly understood. Here we propose that pore fluids play an important role in explaining earthquake rupture speed: the pore pressure may increase sharply at the compressional front during rupture propagation, promoting shear failure ahead of the rupture front and accelerating its propagation into the supershear range. We characterize the transition from sub-Rayleigh to supershear rupture in fluid-saturated rock, and show that the proposed poroelastic weakening mechanism may be a controlling factor for intersonic earthquake ruptures. [ABSTRACT FROM AUTHOR]

Daguangbao (DGB) Landslide (12 × 108 m3) is the largest landslide triggered by the 2008 Ms8.0 Wenchuan Earthquake, in which basal shear failure develops on an interlayer fault at 400 m deep under the ground. After the landslide, a 1.8 km long (in the sliding direction) oblique shear face is exposed. Different kinds of materials in the interlayer fault of DGB landslide are taken for direct shear test, medium scale shear test, in-situ shear test and ring shear test. The test results show that fault material cohesion ranges from 20 to 320 kPa and internal friction angle from 15° to 41°. Shearing strength of interlayer fault materials is related to fragmentation degree of structure. The lower fragmentation degree the more obvious strain softening characteristics of materials, the higher fragmentation degree the poorer shearing resistance of materials. Compared with argillaceous materials in the same fault, the mylonitic materials are of higher shear strength and internal friction angle. Both mylonitic materials and breccia materials are strong in liquefying. In saturated undrained cases, shear strength of fault materials could drop to 9.7°, with S3 down to 0. In saturated undrained dynamic shear conditions, fault internal friction angle could be reduced to 23.1° and 4.2°. It is concluded that low friction feature of fault materials caused by the influence of groundwater is the main reason for destabilization of DGB landslide. [ABSTRACT FROM AUTHOR]

Subduction megathrusts exhibit a spectrum of slip modes, including catastrophic earthquakes. Although the mechanical and frictional properties of materials sampled from subduction zones have been studied extensively, few datasets have been collected for compositions and at pressure and temperature conditions representative of those in situ. The Nankai subduction zone in southwest Japan is a well‐studied margin, and abundant data provide an opportunity to advance our understanding of fault and earthquake physics. Here, we use samples exhumed in the Shimanto and Sanbagawa Belts on Shikoku Island of southwest Japan that represent analogs for materials along the present‐day megathrust at depths of ∼5–>25 km, and we shear these at their peak in situ pressure‐temperature (P‐T) conditions. Effective normal stresses range from 28 to 192 MPa, and temperatures from 105°C to 470°C. We used pore fluid pressures of 45–240 MPa, corresponding to fluid overpressure ratios λ of 0.65 and 0.90. Slip velocities of 0.1–100 μm/s were used, in order to focus on the nucleation of instability and earthquakes. We found predominantly velocity‐strengthening (inherently stable) behavior under all conditions for λ = 0.65. For λ = 0.90, velocity‐weakening behavior was observed at 350°C, with velocity‐strengthening behavior at lower and higher temperatures. The rate/state frictional stability parameter (a‐b) increases with slip velocity at temperatures up to ∼200°C and remains constant or decreases with slip velocity at higher temperatures. Overall, our results demonstrate the potentially important roles of both temperature and slip velocity in controlling the distribution of stress and frictional rheology along subduction thrusts. Plain Language Summary: The largest earthquakes on Earth occur along fault zones at subduction plate boundaries. These earthquakes are controlled, in large part, by the frictional properties of the fault zone materials. However, those properties are not fully understood, and laboratory experiments are key to advancing our knowledge. One example of a subduction zone is the Nankai Trough in southwest Japan. This subduction zone has been the subject of several drilling expeditions, recovering samples from the subsurface, and providing materials used in laboratory experiments. However, the experiments to date focus on materials recovered from depths shallower than those where earthquakes nucleate, and have been performed at temperatures lower than those in earthquake source regions. In this study, we used samples known to come from depths where earthquakes nucleate, and we performed friction experiments at temperatures and pressures relevant for these depths. We find that the frictional properties are primarily dependent on temperature and on the velocity of sliding. Key Points: Friction experiments on samples exhumed in the Shimanto Belt and Sanbagawa Belt at sample‐specific in situ peak PT conditionsBehavior predominantly velocity‐strengthening with velocity‐weakening at 350°CFrictional slip stability shows temperature‐dependent trend with slip velocity [ABSTRACT FROM AUTHOR]

Formulation of the problem. In the work, the most general definition of temperature was discussed and presented, the temporal probability distribution of air temperature was analyzed and evaluated. Temperature has no specific definition. Thus it will be difficult to study the nature of any geophysical phenomena, including the characteristics of temperature distribution, without understanding the modern scientific definition and adjustment of temperature. The aim of the work is to give the most modern reasonable definition of temperature or what the thermometer measures, the answer to which requires a more specific scientific justification, as well as to evaluate the patterns of possible spatiotemporal distribution of air temperature in the territory of Armenia and in the area of the Lake Sevan basin. Methods. To solve the set tasks, the authors used corresponding research and published works as a theoretical basis in the work. In the work, the average monthly data of actual observations of the temperature of the ground surface air layer and the amount of precipitation of the «Center for Hydrometeorology and Monitoring» SNCO of the Ministry of Environment of the Republic of Armenia were used. It was found that temperature is a quantity characterizing the thermal state and radiation of the terrestrial and celestial bodies and, in general, the environment, which is strongly related to the entropy change of the system; temperature is the main thermodynamic characteristic of thermal equilibrium; the thermodynamic and microscopic concepts of temperature coincide; the temperature- heat (energy) difference becomes known in the sense that a system can have high energy but low temperature. The authors applied the following research methods in the article: mathematical and statistical, extrapolation, analysis, analogy, correlation, cartographic. Results. Energy depends on the geometry (dimensions) of the system, but temperature does not. A trend of increasing air temperature is observed in the RA territory, which is also a result of the entropy change of the system. It can change very quickly, depending on the environmental factors in the given area (the growth rate of greenhouse farms, the artificial filling of valleys, which are wave carriers of air flow, the relentless use of green spaces for the purpose of public buildings, and other factors) in the process of disrupting the excessively permissible norms, which are currently separate needs serious research and prevention. The long-term variability of surface air temperature in the area of the Lake Sevan basin is analyzed. The analysis carried out made it possible to give a quantitative assessment characterizing the climate change in this region over the past 98 years. An analysis of the observational data showed that the trend of climate warming is confirmed by an increase in air temperature both in winter and over a long period of time. The change in surface air temperature occurs at a rate of 0.002 ºС/year to 0.012 ºС/year and is generally 0.008 ºС/year (or 0.08 ºС/10 years) for all analyzed stations. The results obtained confirm the presence of two periods of warming observed in 1927–1970 and 1971–2021. All the results obtained in the course of the work testify to the trend of climate mitigation in the area of the Lake Sevan basin at the end of the 20th - beginning of the 21st century. [ABSTRACT FROM AUTHOR]

Earthquakes often occur in regions with complex material structure, such as sedimentary basins or mantle wedges. However, the majority of co-seismic modelling studies assume a simplified, often homogeneous elastic structure in order to expedite the process of model construction and speed up calculations. These co-seismic forward models are used to produce Green's functions for finite-fault inversions, so any assumptions made in the forward model may introduce bias into estimated slip models. In this study, we use a synthetic model of a sedimentary basin to investigate the impact of 3-D elastic structure on forward models of co-seismic surface deformation. We find that 3-D elastic structure can cause changes in the shape of surface deformation patterns. The magnitude of this effect appears to be primarily controlled by the magnitude of contrast in material properties, rather than the sharpness of contrast, the fault orientation, the location of the fault, or the slip orientation. As examples of real-world cases, we explore the impact of 3-D elastic structure with a model of the Taipei basin in Taiwan and a simulated earthquake on the Sanchaio fault, and with a 3-D geologic model of the San Francisco Bay Area and a slip model of the 1984 Morgan Hill earthquake on the Calaveras fault. Once again, we find that the presence of the basin leads to differences in the shape and amplitude of the surface deformation pattern, but we observe that the primary differences are in the magnitude of surface deformation and can be accounted for with a layered elastic structure. Our results imply that the use of homogeneous Green's functions may lead to bias in inferred slip models in regions with sedimentary basins, so, at a minimum, a layered velocity structure should be used. [ABSTRACT FROM AUTHOR]

[Display omitted] • Weakly cohesive Chitosan microcapsules were deformed up to breakup in an extensional flow with orthogonal observations. • Two mechanisms of rupture regimes of microcapsules were revealed: fluid-like and solid-like behaviours. • The dual response of microcapsule rupture in flow is closely correlated to the shell structure. The controlled rupture of a core–shell capsule and the timely release of encapsulated materials are essential steps of the efficient design of such carriers. The mechanical and physico-chemical properties of their shells (or membranes) mainly govern the evolution of such systems under stress and notably the link between the dynamics of rupture and the mechanical properties. This issue is addressed considering weakly cohesive shells made by the interfacial complexation of Chitosan and PFacid in a planar extensional flow. Three regimes are observed, thanks to the two observational planes. Whatever the time of reaction in membrane assembly, there is no rupture in deformation as long as the hydrodynamic stress is below a critical value. At low times of complexation (weak shear elastic modulus), the rupture is reminiscent of the breakup of droplets: a dumbell or a waist. Fluorescent labelling of the membrane shows that this process is governed by continuous thinning of the membrane up to the destabilization. It is likely that the membrane shows a transition from a solid to liquid state. At longer times of complexation, the rupture has a feature of solid-like breakup (breakage) with a discontinuity of the membrane. The maximal internal constraint determined numerically marks the initial location of breakup as shown. The pattern becomes more complex as the elongation rate increases with several points of rupture. A phase diagram in the space parameters of the shear elastic modulus and the hydrodynamic stress is established. [ABSTRACT FROM AUTHOR]

Surface fault ruptures damage structures which are located at the intersecting zones of active faults. It is essential to consider the undesirable effects of surface fault ruptures when designing structures. Geotechnical measures such as reinforced soil foundations effectively mitigate the hazards related to surface faults. The present work conducted a series of tests on foundations reinforced with geosynthetics, including geogrids, geocells and geogrid-geocell layers. These tests simulated the behavior of 1.5 m-wide strip footings located in 6-m thick alluvium that had been displaced 60 cm. A total of 12 disparate tests in terms of the number and type of reinforcement were conducted at a scale factor of 10. Image analysis of the results indicated desirable behavior for reinforced soil foundations in terms of reduced angular distortion, uniform settlement and deviation of the fault path. For normal fault rupture, the angular distortion of foundations reinforced by one geogrid layer, one geocell layer, one geogrid-geocell layer or two or three geogrid layers decreased by 60%, 30%, 70%, 80% and 80%, respectively. These results also revealed that an increase in the number of geogrid layers to more than two layers caused an insignificant decrease in angular distortion. The decrease in angular distortions observed for soil foundations reinforced by one geogrid layer, one geocell layer and one geogrid-geocell layer were 7%, 16% and 40%, respectively, for reverse faulting. The performance of a reinforced soil foundation subjected to normal faulting was more acceptable than that for reverse faulting. [ABSTRACT FROM AUTHOR]

Aseismic slip is a stable fault slip, which allows strain to be relieved smoothly. Aseismic slip prevents the earthquake propagation, but it could nucleate an earthquake elsewhere. Understanding the mechanism of aseismic slip is promising in revealing the seismic cycle. Experimental evidence showed clay-rich fault gouge bears a low-friction strength, and the friction is strengthened with slip velocity (velocity-strengthening), which was thought to support aseismic slip. Clay minerals are comprised of platy crystalline layers with water intercalated between them, which may act as a lubricant. Sliding between clay layers was suspected to support aseismic slip but lacked a clarified mechanistic insight. We use non-equilibrium molecular dynamics simulations to show that shear-induced interlayer sliding is frictionally weak and velocity-strengthening, which evidences the role of clay minerals in aseismic slip. We find that interlayer water is a viscous fluid at most times, which explains the shear response of interlayer sliding. Depending on temperature and pressure conditions, intercalated water can be monolayer or bilayer, fluidic or ice like. Shear induces icelike water to transform into fluidic water, which happens as a stick-slip phenomenon reflecting a first-order transition. Increased pore fluid pressure leads to the transformation from monolayer to bilayer intercalated water, resulting in a lower friction strength and enhanced velocity-strengthening behavior. Our work suggests that disclosing the hydration state of a clay mineral is preliminary when studying fault mechanics. [ABSTRACT FROM AUTHOR]

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• Unusual large shallow crustal faulting occurred above a deep, long-duration seismic swarm along the Noto Peninsula. • The 2024 M W 7.5 earthquake is the largest recorded along the Noto Peninsula, had a slow initial rupture expansion. • Weak initial seismic energy indicates a gradual nucleation process, possibly influenced by deeper fluid accumulation. • A dominant deep large-slip patch and a weaker shallow slip suggests non-uniform fault properties and fluid migration effects on fault weakening. A damaging M W 7.5 earthquake struck the western coast of Japan along the Noto Peninsula on January 1, 2024. The initiation of large shallow earthquakes along the Noto Peninsula, particularly above deeper long-duration patchy seismic swarms, presents an unusual seismic phenomenon that warrants in-depth investigation of their interactions. The 2024 earthquake nucleated with an initial low average rupture velocity of 0.5–1.0 km s-1 near the up-dip end of a long-lasting seismic swarm that commenced in November 2020. Analysis of dense seismic, geodetic, and tsunami observations provides good resolution of large shallow slip in the crust below the peninsula and extending offshore to the northeast, revealing a heterogeneous slip distribution characterized by bilateral two-stage rupture expansion during the faulting. Up to 8 m of slip occurred in several patches along ∼150 km of the southeastward-dipping thrust fault, which extends to near the seafloor along the northwest side of the peninsula. Up to 5 m of uplift occurred along the peninsula's northwestern coast. Up-dip fluid migration appears to have weakened the shallow fault prior to failure and influenced the initial slow rupture expansion, highlighting the need to monitor the evolution of worldwide swarms. [ABSTRACT FROM AUTHOR]

The 2022 M W 6.6 Luding earthquake occurred on the Moxi segment of the Xianshuihe fault at the southeast margin of Tibetan Plateau, China. To assess the seismic potential of the Moxi segment, we examine the rupture process of the mainshock and aftershock sequence, along with historical seismicity. Our preferred slip model inverted from teleseismic body waves and regional GNSS static displacements shows a dominant southeastward rupture consisting of two distinct, prominent slip patches along strike extending by ∼15 km, with a peak slip of ∼2.8 m, approximately balancing the slip deficit since the last major earthquake in 1786. The northern section of the Moxi segment experienced minor coseismic slip, which, together with the significant slip deficits and positive Coulomb failure stress change induced by the 2022 mainshock indicates a high seismic potential. Several aftershock clusters are distributed along or near the Moxi segment, with strike-slip focal mechanisms around the downdip edge of the coseismic slip area at ∼8‐12 km. At the eastern flank of Mt. Gongga, another cluster of normal faulting aftershocks is located at shallower depths of ∼3‐7 km, with high seismicity rate over ∼9 months including two other M5 sequences in January and February 2023. Similar intense shallow normal faulting activity had occurred after the impoundment of the nearby Dagangshan reservoir in 2015. We speculate that some NW-SE trending normal faults were initially developed by the gravitational collapse of Mt. Gongga underneath the eastern flank, further weakened by fluid flow, as supported by the existence of hot springs and water impoundment, and reactivated by the tensional stress change induced by the 2022 mainshock. These results have important implications for assessing the seismic hazard in and around the Moxi segment, and the potential interplay between strike-slip fault and nearby mountain areas. • The 2022 Luding earthquake ruptured the southern end of the Xianshuihe Fault. • Seismic and geodetic observations reveal dominant southward rupture over ∼15 km. • Positive ΔCFS for the Moxi segment to the north indicates a high seismic potential. • Gravitational collapse and stress transfer explain normal faulting under Mt. Gongga. • Hot springs near Mt. Gongga imply fluid control on the fault strength and seismicity. [ABSTRACT FROM AUTHOR]

On 18 December 2023, the Ms 6.2 Jishishan earthquake struck the border region of Gansu province and Qinghai province in the northeastern Tibetan Plateau in China. Field investigations revealed that the 2023 Ms 6.2 Jishishan earthquake produced a ∼1.2-km-long coseismic surface deformation zone with the characteristic centimeter-sized uplift and bulge in the range of 1–13 cm (generally<5 cm), which was mainly restricted to a narrow corridor of 40–50 m in width along an previously-unknown frontal blind fault of the North Lajishan thrust fault zone. In spatial location, the coseismic surface deformation zone corresponds to the core of a late Cenozoic anticline on the hanging wall of blind fault, indicating that the coseismic surface uplift was constrained by the pre-existing tectonic environment. The North Lajishan thrust fault zone is composed of the west branch fault (F1), east branch fault (F2) and the frontal blind fault (F3), the surveying results document that only the frontal thrust fault (F3) is the Holocene seismically active fault. Thus, the seismogenic fault of the 2023 Ms 6.2 Jishishan earthquake was suggested to be the F3 fault, indicating the northeastward propagation and expansion of the most recent earthquake activities within the North Lajishan thrust fault zone related to the ongoing northeastward shortening of the northeastern Tibetan Plateau accommodating the Eurasia-India continental collision. • The coseismic surface deformation is characterized by centimeter-scale uplift and bulge. • The seismogenic fault of the 2023 Ms 6.2 Jishishan earthquake is the blind frontal thrust fault F3. • Imbricated thrust-fold system is one type of important seismogenic structure. [ABSTRACT FROM AUTHOR]

Co-seismic failure can occur on newly formed or on inherited structures. However, understanding their surface pattern is challenging when pre-existing structural anisotropies control rupture propagation. We focus here on the Pescopagano Fault (PF), considered part of the extensional fault system that ruptured during the 1980, Mw 6.9 earthquake in Southern Italy. Although the mainshock fault (Irpinia Fault) produced ∼ 40 km of NW-SE trending ground ruptures, these were not observed on a buried antithetic fault located to the northeast of the main fault and defined solely by seismological data. The PF studied here is part of an exposed fault array that spatially coincides with the trace of the antithetic fault. To better assess existing seismotectonic models for the Irpinia fault system, we investigated: i) whether ground ruptures occurred on the PF during past earthquakes, and ii) to what degree surface and deep faults are linked. Paleo-seismological trenches document that the PF has not released surface-rupturing earthquakes during the last ∼13–20 ka. Structural data suggest that the PF developed to accommodate the relaxation of a Pliocene thrust-fold system after the demise of thrusting. Results of this work highlight that the PF may be an inherited Pliocene or Early Pleistocene structure that does not reach the ∼10–15 km seismogenic depth typical of this region. In this scenario, the upward propagation of the antithetic fault from seismogenic depths towards the surface during a 1980-type earthquake may be impeded by a mélange layer developed during the growth of the Southern Apennines thrust belt and interposed between the deep antithetic fault and the upper crustal faults. We cannot exclude, however, that the PF may be activated during very large but infrequent and non-characteristic earthquakes on the Irpinia fault system. • Earthquake surface ruptures may be diffuse during large earthquakes. • Pre-existing structural fabrics controls propagation of co-seismic ruptures. • Inherited faults may not be linked to seismogenic depths. [ABSTRACT FROM AUTHOR]