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Earthquake environmental effects may significantly contribute to the damage caused by seismic events; similar to ground motion, the environmental effects are globally stronger in the vicinity and decrease moving away from the epicenter or seismogenic source. To date, a single intensity prediction equation (IPE) has been proposed in the Italian Apennines for intensity scale dealings with environmental effects: the Environmental Seismic Intensity (ESI-07). Here, we evaluate the sensitivity of the IPE with respect to input data and methodological choices and we propose IPEs with global validity for crustal normal faults. We show the strong influence of input data on the obtained attenuation investigating the 1980 Irpinia–Basilicata (Southern Italy) earthquake. We exploit a dataset of 26 earthquakes to build an IPE considering the epicentral distance. We also propose an IPE considering the distance from the fault rupture, which is derived from a dataset of 10 earthquakes. The proposed equations are valid for normal faults up to 40 km from the epicenter/fault and may flank other models predicting ground motion or damage to the built environment. Our work thus contributes to the use of the ESI-07 scale for hazard purposes. [ABSTRACT FROM AUTHOR]

Normal fault systems may grow by the lateral propagation of segments, yet little is known about the timescales over which this may occur and the implications for rift propagation. Footwall bedrock river networks provide a means to delineate the recent fault displacement patterns since erosional landscapes are sensitive recorders of rock uplift histories. Here, we analyze river profiles and map knickpoints in the Ruo River network and several adjacent rivers draining the footwalls of the en‐echelon Thyolo‐Muona‐Camacho border fault system of the Lower Shire Graben, southern East African Rift System. Using parameters calibrated in previous studies, we estimate the knickpoint initiation times and use linear river profile inversions to understand footwall uplift histories. Abrupt increases in bedrock river channel steepness indices approaching the faults suggest a recent acceleration in fault slip rates. Linear inversion of the bedrock river profiles reveals that footwall uplift rates accelerated from ∼0.1 to 0.3 mm/yr at ∼2–3 Ma in the Thyolo‐Muona footwalls. Later, at ∼0.75–1.0 Myr, farther southeast, the Camacho footwall river profiles show an increase in rock uplift rate from ∼0.05 to 0.2 mm/yr, but this signal decays moving southeast. Modern uplift rates along the Thyolo‐Muona section attain 0.33–0.56 mm/yr, and Camacho 0.19–0.29 mm/yr. We propose that within <2 Myr timescale, the border fault grew by an initial (Early Pleistocene) accelerated slip and hard linkage of the already‐nucleated segments, later followed by the southeastward lateral propagation of the system toward the adjacent rift, the Nsanje Graben. Key Points: Footwall rock uplift rates accelerated from ∼0.1 to 0.3 mm/yr at ∼2–3 Ma in the footwalls of the Thyolo‐Muona sections of the border faultLater, at ∼0.75–1.0 Myr, the Camacho section nucleated further southeast, with footwall uplift rates increasing from ∼0.05 to 0.2 mm/yrThe growth of Lower Shire Graben's border fault system demonstrates a laterally propagating fault system, establishing itself within <2 Myrs [ABSTRACT FROM AUTHOR]

Abstract Active faults in the earthquake region are consistently regarded as a potential geological hazard to the construction and operation of railway engineering. However, the effects of normal faulting on railway embankments have not been investigated thoroughly. For bridging this knowledge gap, three-dimensional finite element analysis considering the influence of faulting offset, the soil layer’s thickness, the fault dip angle and the embankment cross-fault angle are conducted to clarify the normal faulting effects on the railway embankment. Emphasis is given to the stress and strain characteristic in the fault rupture outcropping regions on the embankment, the deformation of the embankment centerline for design purposes, and the determination of the affected zones for railway embankment preservation. The analysis shows that the normal fault rupture outcropping regions on railway embankment are tensile yield in most cases. The existence of the soil layer and its thickening would widen the affected zones and the regions where the fault ruptures outcrops. The fault dip angle and the cross-fault angle of the embankment have a complex effect on the behaviors of the crossing embankment. The depth of the subsidence zone of the embankment would increase with the decrease of the fault dip angle and the large fault dip angle would change the primary fault rupture to be a compressive one directly above the fault line. If the embankment crosses the fault line obliquely, the curvature radius of the centerline would hardly meet the design code.

Abstract With the large-scale construction of oil and gas pipelines, the safety issues of long-distance buried pipelines in the service and construction have become increasingly prominent. The complex geological and topographical conditions of the special zone will put forwards extremely high requirements on pipe trench laying backfill materials and construction technology. For example, pipelines are inevitable to cross the active fault, while the trench backfilled with soil has limitations in protecting them from failure under the active fault displacement caused by the earthquake. Therefore, it is necessary to study the pipe–soil interaction mechanism, determine the stress state of the pipeline and propose a new backfilling material that can protect the pipeline from failure. Foam concrete (FC) provides a new choice to backfill the buried pipeline trench due to its high-homogeneity, lightweight, controllable-strength, and self-compacting. To further determine the applicability of the FC, the pipe-FC interaction mechanism is studied. Then, a FE model of the FC-pipeline-soil interaction system is established by Abaqus to quantitatively analyze the applicability of the FC based on the experimental data of the mechanical performance of the FC. It proves that using FC as trench backfill material has a noticeable protective effect on the pipeline under the earthquake-induced displacement of the normal fault. Furthermore, FC has a better protective effect on the pipeline subjected to compressive than tensile. Therefore, the reference for applying FC in trench backfilling of pipelines crossing normal fault is provided.

Active faults in the earthquake region are consistently regarded as a potential geological hazard to the construction and operation of railway engineering. However, the effects of normal faulting on railway embankments have not been investigated thoroughly. For bridging this knowledge gap, three-dimensional finite element analysis considering the influence of faulting offset, the soil layer's thickness, the fault dip angle and the embankment cross-fault angle are conducted to clarify the normal faulting effects on the railway embankment. Emphasis is given to the stress and strain characteristic in the fault rupture outcropping regions on the embankment, the deformation of the embankment centerline for design purposes, and the determination of the affected zones for railway embankment preservation. The analysis shows that the normal fault rupture outcropping regions on railway embankment are tensile yield in most cases. The existence of the soil layer and its thickening would widen the affected zones and the regions where the fault ruptures outcrops. The fault dip angle and the cross-fault angle of the embankment have a complex effect on the behaviors of the crossing embankment. The depth of the subsidence zone of the embankment would increase with the decrease of the fault dip angle and the large fault dip angle would change the primary fault rupture to be a compressive one directly above the fault line. If the embankment crosses the fault line obliquely, the curvature radius of the centerline would hardly meet the design code. [ABSTRACT FROM AUTHOR]

Accurate earthquake source parameters are crucial for understanding plate tectonics, yet, it is difficult to determine these parameters precisely for offshore events, especially for outer‐rise earthquakes, as the limited availability of direct P or S wave data sets from land‐based seismic networks and the unsuitability of simplified 1D methods for the complex 3D structures of subducting systems. To overcome these challenges, we employ an efficient hybrid numerical simulation method to model these 3D structural effects on teleseismic P/SH and P‐coda waves and determine the reliable centroid locations and focal mechanisms of outer‐rise normal‐faulting earthquakes in northeastern Japan. Two M6+ events with reliable locations from ocean bottom seismic observations are utilized to calibrate the 3D velocity structure. Our findings indicate that 3D synthetic waveforms are sensitive to both event location, thanks to bathymetry and water reverberation effects, and the shallow portion of the lithospheric structure. With our preferred velocity model, which has Versus ∼16% lower than the global average, event locations are determined with uncertainties of <5 km for horizontal position and <1 km for depth. The refined event locations in a good match between one of the nodal strikes and the high‐resolution bathymetry, enabling the determination of the causative fault plane. Our results reveal that trench‐ward dipping normal faults are more active, with three parallel to the trench as expected, while five are associated with the abyssal hills. The significant velocity reduction in the uppermost lithosphere suggests abundant water migrating through active normal faults, enhancing both mineral alteration and pore density. Plain Language Summary: The subduction of oceanic plates plays a crucial role in recycling earth materials and generating the largest earthquakes and tsunamis. This process causes significant bending of the oceanic plate near the trench, where forces from frictional coupling on the plate interface and far‐field subduction loading act in opposite directions, forming a gentle bulge on the seafloor termed the outer‐rise region. This region is rich in shallow bending‐related earthquakes at shallow depths and is characterized by rough bathymetry bounded by faults. Identifying the relationship between these earthquakes and their hosting faults is critical for understanding the seismic and tsunami hazards and fault development in the outer rise. However, building up this link is impeded by large uncertainties of earthquake source parameters. Here, we employ an advanced numerical wavefield simulation approach to precisely handle the structural complexity near 8 ∼ M6 outer‐rise earthquakes, which allows use of far‐field seismic waveform data to constrain source parameters. Reliable earthquake locations and focal mechanisms, along with high‐resolution bathymetry, enable us to identify the causative faults. Dramatically low velocity structure of the subducting oceanic plate is also revealed through this process, which suggests a fluid‐rich outer rise region that efficiently recycles water into the deeper earth. Key Points: Centroid location and focal mechanism of outer‐rise earthquakes were reliably determined through 3D modeling of teleseismic body wavesAlong with high‐resolution bathymetry, reliable source parameters allow us to identify the ruptured faults hosting these normal events3D waveform modeling required a Versus ∼16% lower than the global average, suggesting a fluid‐rich oceanic lithosphere at the outer rise [ABSTRACT FROM AUTHOR]

With the large-scale construction of oil and gas pipelines, the safety issues of long-distance buried pipelines in the service and construction have become increasingly prominent. The complex geological and topographical conditions of the special zone will put forwards extremely high requirements on pipe trench laying backfill materials and construction technology. For example, pipelines are inevitable to cross the active fault, while the trench backfilled with soil has limitations in protecting them from failure under the active fault displacement caused by the earthquake. Therefore, it is necessary to study the pipe–soil interaction mechanism, determine the stress state of the pipeline and propose a new backfilling material that can protect the pipeline from failure. Foam concrete (FC) provides a new choice to backfill the buried pipeline trench due to its high-homogeneity, lightweight, controllable-strength, and self-compacting. To further determine the applicability of the FC, the pipe-FC interaction mechanism is studied. Then, a FE model of the FC-pipeline-soil interaction system is established by Abaqus to quantitatively analyze the applicability of the FC based on the experimental data of the mechanical performance of the FC. It proves that using FC as trench backfill material has a noticeable protective effect on the pipeline under the earthquake-induced displacement of the normal fault. Furthermore, FC has a better protective effect on the pipeline subjected to compressive than tensile. Therefore, the reference for applying FC in trench backfilling of pipelines crossing normal fault is provided. [ABSTRACT FROM AUTHOR]

Recovering the seismic history of multiple segments within a fault system provides a spatiotemporal framework for the fault activity across the system. This kind of data is essential for improving our understanding of how faults interact during earthquake cycles and how they are distributed within a fault system. Bedrock fault scarps, reaching up to 10‐m height, are abundant across the Bet Kerem fault system, Galilee, northern Israel. Using the 36Cl exposure dating method, we recovered the last 30 ka scarp exhumation history of three fault segments from the Bet Kerem fault system. Results indicate that the three faults were active simultaneously in at least three distinguished activity periods, during which a minimum of 1.2 m of surface rupturing occurred in each period. The synchronized activity and total surface rupture at each activity period suggest that the three dated segments were ruptured simultaneously by the same earthquake. That is, a multi‐segment rupture earthquake and that each activity period included a cluster of at least two large multi‐segment earthquakes. The results also indicate a recurrence interval between clusters of 3.5–4.5 ka and the existence of a seismic super cycle with a recurrence interval of about 13 ka. Plain Language Summary: Surface rupture occurs when a large earthquake caused by movement along a fault, breaks through the Earth's surface. The 36Cl cosmogenic dating is used to recover past earthquakes that generate surface rupture. Using this method to constrain the fault activity over multiple earthquake cycles and across fault systems provides essential data to understand how earthquakes behave along fault systems and how faults interact during the earthquakes. We recovered the last 30 ka surface rupture history of three fault segments, each approximately 5 km in length, from the Bet Kerem fault system, northern Israel, using the 36Cl exposure dating method. Results indicate that the three segments were active in at least three distinguished periods, in each of which a minimum of 1.2 m of surface rupturing occurred at each fault segment. The amount of surface rupture observed at each of the segments is too large to be generated by one single earthquake that only ruptures the fault segment. However, when all segments are considered together their total length corresponds well with the amount of offset. We, therefore, suggest that the large surface rupture observed at each activity period is caused by large earthquakes that ruptured the three dated segments at once. Key Points: The earthquake history of three normal fault segments is reconstructed with 36Cl exposure datingOver the last 30 ka, the three fault segments ruptured the earth's surface simultaneously in at least three distinguished periodsDuring each activity period, at least two earthquakes occurred very closely in time, each resulting in a rupture of the three segments [ABSTRACT FROM AUTHOR]

Ground deformation on the Earth’s surface layer is strongly affected by the nonlinearity of geomaterials. However, the formation process of such deformation has yet to be described in a unified manner based on mechanics. The present study focuses on the normal faults in a submarine ground with highly developed soil skeleton structures and attempts to reproduce the process of normal fault formation associated with the tilting of a horizontally deposited submarine ground using an elastoplastic finite element simulation. The simulation was conducted using the soil–water coupled finite deformation analysis code GEOASIA, which incorporates an elastoplastic constitutive equation of the soil skeleton based on the modified Cam-clay model and the soil skeleton structure concept. The key findings are as follows:1) Normal faults are formed from the ground surface to depth as shear bands, where shear strain is localized while exhibiting softening behavior with plastic volume compression.2) Multiple normal faults are almost equally spaced and parallel to each other, with the inter-fault blocks rotating backward. The morphology of normal faults formed by the tilting of the ground shows domino-style characteristics.3) The degree of the soil skeleton structure influences the formation of normal faults.This study demonstrates that elastoplastic geomechanics can explain the formation process of ground deformation, which has usually been interpreted from the perspectives of geomorphology and geology.

The paper presents a tectonic map of Sakhalin Island showing digitized faults derived from 1:1,000,000 scale tectonic maps and identified by geological surveys (detailed on 1:200,000 and 1:50,000 scale maps). The structural geological data on the kinematics of faults have been compared with seismological data on the earthquake focal mechanisms. A reasonable correspondence of these data has been obtained. The predominant kinematic type of faults is thrust/throw in the southern and northern parts of Sakhalin Island. In the central part of Sakhalin, a mixing of fault kinematic types is observed, mainly thrust faults with rare normal and strike-slip faults. Two uninformative zones have been identified with virtually no data on both structural geology and seismology. The earthquake focal mechanisms with a strike-slip component are dominant at their boundaries.

Fault movement during earthquakes is a geotechnical phenomenon threatening buried pipelines and with the potential to cause severe damage to critical infrastructures. Therefore, effective prediction of pipe displacement is crucial for preventive management strategies. This study aims to develop a fast, hybrid model for predicting vertical displacement of pipe networks when they experience faulting. In this study, the complex behavior of soil and a buried pipeline system subjected to a normal fault is analyzed by using an artificial neural network (ANN) to generate predictions the behavior of the soil when different parameters of it are changed. For this purpose, a finite element model is developed for a pipeline subjected to normal fault displacements. The data bank used for training the ANN includes all the critical soil parameters (cohesion, internal friction angle, Young's modulus, and faulting). Furthermore, a mathematical formula is presented, based on biases and weights of the ANN model. Experimental results show that the maximum error of the presented formula is 2.03%, which makes the proposed technique efficiently predict the vertical displacement of buried pipelines and hence, helps to optimize the upcoming pipeline projects. [ABSTRACT FROM AUTHOR]

Since in extensional environments less differential stress is needed for rock fracture, earthquakes are usually triggered with less energy. In the present study, by determining the amount of energy along the normal fault during the collapse of the hanging wall block, which is dependent on the calculation of the volume of the hanging wall block, while achieving the main goal of the study, geometrical data including the volume of the hanging wall block can be obtained. The main foundation of the current seismic model is based on the theory of elastic rebound, in which the release of accumulated elas tic energy occurs during the interseismic period. Finite elements, including triangular linear Lagrange elements and conditions of lateral tension changes at the base of the lithosphere affected by viscous-plastic s tretching in the upper mantle, have been used for numerical analysis. The results showed that the increase in the magnitude of the earthquake is affected by the increase in the length of the rupture, and the amount of finite deformation caused by seismic sequences is related to the length of the rupture and is about five times the depth of the hypocenter. Assuming a dip of about 45 degrees for the conjugate wedge with the fault activated during the nucleation of an earthquake, the three volumes of the falling wedge during the earthquake s tage for three lengths of 44, 56, and 78 km with depths of 8, 11.5, and 16.6 km, respectively, well indicate the direct correlation of the fault length with the displacement of the fault and the volume of the hanging wall block. [ABSTRACT FROM AUTHOR]

Daqingshan piedmont fault is located in the northern margin of Hetao basin and has been active strongly since the Late Quaternary. Previous researchers had conducted extensive research on the characteristics of paleoseismic in this area, but limited by the dating techniques and the fact that there were fewer data available on the same fault profile that can effectively constrain paleoseismic events, and fewer profiles that can reveal more paleoseismic events. This paper explores the excavation of an paleoseismic trench on the east side of Lianhuashan in the western section of Tuyouqi of the Daqingshan piedmont fault, using Optically Stimulated Luminescence data, and combineing with the age data of previous exploration trenches. By using the fault successive limit method, it is found that the western section of the Tuyouqi fault has experienced five paleoseismic events approximately 11500 years ago, with an average recurrence interval of 2260 years. The five paleoseismic events in this section of the fault, from new to old, are 1.28 to 1.42 ka, 3.41 to 3.60 ka, 4.08 to 5.01 ka, 8.26 to 9.32 ka, and 10.70 to 11.30 ka, respectively. The latest event of activity should be the earthquake of 849 AD. Meanwhile, the trench exploration revealed that the fault in this section exhibits a normal fault nature, with an inclination angle between 58 and 77 degrees. According to empirical formula, the potential seismic capacity of the Baotou section, the western section of Tuyouqi, and the western section of Tuzuoqi are around MW6.8～7.1, MW6.8～7.1 and MW7.1～7.2, respectively. The magnitude obtained by the empirical formula in this paper is relatively small, and there may be cascade rupture. In the later stage, it is necessary to conduct a comprehensive evaluation of the risk of the western section of Daqingshan piedmont fault combined with other means.

Earthquake environmental effects may significantly contribute to the damage caused by seismic events; similar to ground motion, the environmental effects are globally stronger in the vicinity and decrease moving away from the epicenter or seismogenic source. To date, a single intensity prediction equation (IPE) has been proposed in the Italian Apennines for intensity scale dealings with environmental effects: the Environmental Seismic Intensity (ESI-07). Here, we evaluate the sensitivity of the IPE with respect to input data and methodological choices and we propose IPEs with global validity for crustal normal faults. We show the strong influence of input data on the obtained attenuation investigating the 1980 Irpinia–Basilicata (Southern Italy) earthquake. We exploit a dataset of 26 earthquakes to build an IPE considering the epicentral distance. We also propose an IPE considering the distance from the fault rupture, which is derived from a dataset of 10 earthquakes. The proposed equations are valid for normal faults up to 40 km from the epicenter/fault and may flank other models predicting ground motion or damage to the built environment. Our work thus contributes to the use of the ESI-07 scale for hazard purposes.

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Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The relationship between normal fault displacement (D) and length (L) varies due to numerous factors, including fault size, maturity, basin tectonic history, and host rock lithology. Understanding how fault D and L relate is useful, given related scaling laws are often used to help refine interpretations of often incomplete, subsurface datasets, which has implications for hydrocarbon and low-carbon energy applications. Here we provide a review of D/L scaling laws for normal faults, discuss factors that could influence these relationships, including both geological factors and errors in measurement, and provide a critique of previously published D/L databases. We then present our newly assembled database of 4059 normal faults from 66 sources that include explicit information on: 1) fault length and displacement, 2) host rock lithology, 3) host basin tectonic history, and 4) maturity, as well as fault D and L through time when these data are available. We find an overall scaling law of D = 0.3L0.92, which is similar to previously published scaling equations and that varies in response to the aforementioned geological factors. Our data show that small faults (<1m length) tend to be over-displaced compared to larger faults, active faults tend to be under-displaced compared to inactive faults, and faults with stiffer host rock lithologies, like igneous and carbonate rocks, tend to be under-displaced with respect to faults within softer, more compliant host rocks, like clastic sedimentary rocks. Our dynamic D/L through time data show that faults follow the hybrid fault growth model, i.e., they initially lengthen, during which time they will appear under-displaced, before accumulating displacement. To the best of our knowledge, this is the first comprehensive, integrated, critical study of D/L scaling laws for normal faults and the factors influencing their growth. These revised relationships can now be utilized for predicting fault length or displacement when only one variable is available and provide the basis for general understanding D/L scaling laws in the context of normal fault growth. This underpinning database is open-access and is available for analysis and manipulation by the broader structural geology community. [ABSTRACT FROM AUTHOR]

The recent article of Loreto et al. (2021) reported new stratigraphic and structural data of the Tyrrhenian backarc basin and used them to propose a new model of crustal architecture of the basin including oceanic sectors. However, we want to open a discussion on the inconsistencies between the interpreted tectonic structures, as well as the age of faults and the data observations. In particular, data analyses and interpretations of the authors do not fully support the structural and isopach maps and models presented. Furthermore, the authors have not discussed previous published data/interpretations on timing and structural style of the rifting of the region. [ABSTRACT FROM AUTHOR]

Karya Murni is one of the areas in the northern arm of Sulawesi that has been tectonically influenced. Tectonic processes have implications for the formation of rocks and geological features that have the potential to be developed into geodiversity sites. The development of geological features as a geodiversity site in aspiring geopark Gorontalo can protect valuable geological features from frequent degradation. This research aims to analyze and conduct quantitative assessments of geological diversity in Karya Murni, Gorontalo. The research method used is field observation, laboratory analysis, and geodiversity assessment. Field observations included observing landform, collecting rock samples, and measuring geological structures. Field observations were also carried out to observe aspects of the geodiversity assessment which included science, education, tourism, and risk degradation. Laboratory analysis consists of geomorphological analysis, petrographic analysis, and geological structure data analysis. Geodiversity assessment uses the Geological Survey Center of Indonesia assessment. The results suggest that the geomorphology of the study area can be divided into four geomorphic units - the volcanic hills, denudational hills, Karst hills, and fluvial plain units. The stratigraphy of the research area is divided into four units from the age of the early Eocene to the Holocene - the andesite lava, volcanic breccia, reef limestone, and alluvial deposit units. The geological structure of the study area is a trending northeast–southwest to northwest–southeast. Active faults at the location of the study area consist of the Apitalawu normal fault. At recent states, generally geosites of the Karya Murni have moderate scientific values, the low educational and touristic values and high risk of degradation. The geodiversity potential of the research area can be utilized for further research and education.

Analyses of active and past normal fault behaviour in extensional settings provide key insights into regional-scale tectonic processes driven by plate boundary forces. To better understand past tectonic environments in the Tāmaki Makaurau-Auckland region of northern Aotearoa-New Zealand, we examine normal faults with Miocene to Quaternary movements dissecting the Early Miocene Waitematā Group. Structural data were collected from coastal outcrops, including fault geometry and kinematics, and reveal a dominant NE-trending strike direction, indicating NW-SE extension. Faults dissecting coeval and younger Waitākere Group rocks west of the study site exhibit the same NE-striking fabric, and thus may represent the westward continuation of Waitematā Group extensional structures. Furthermore, a NE-trending normal fault fabric is present within the adjacent Taranaki Basin, suggesting that the observed extension in the Waitematā Group was widespread over northern Aotearoa, with some extension still occurring today in southern parts of the Taranaki Basin. We propose that many of the observed normal faults in the Waitematā Group represent the northern portion of the Taranaki Basin fault system, with the Taranaki faults likely representing the younger continuation of the extension recorded in the Waitematā Basin, resulting from the migration of back-arc extension due to roll-back of the Hikurangi subduction margin. [ABSTRACT FROM AUTHOR]

Although the structural response of pipelines has been studied in relation to different geohazards, few studies have focused on the behaviour of flexible pipeline joints. In this paper, the response of a bell-and-spigot joint in a 600 mm dia. lined-corrugated high-density polyethylene (HDPE) pipe was investigated under differential ground movements imposed using a facility that simulates a normal fault. Two experiments were undertaken in this facility. In the first experiment, the kinematic responses of the pipe joint (i.e. axial, shear displacements and rotational angles) were measured using particle image velocimetry and string potentiometers. Strains were also monitored using optical fibres. In the second experiment, the pipe was sealed and leakage of the joint was captured through monitoring the internal vacuum pressure of the pipe. The results show that axial shortening, rotational angle and shear displacement of the pipe joint increased with increasing fault offsets. The joint began to leak when axial shortening, rotational angle and shear displacement of the pipe joint were 0·65 mm, 0·44° and 3·40 mm, respectively, and the joint clearly lost its functionality when those values reached 0·85 mm, 0·58° and 4·32 mm. [ABSTRACT FROM AUTHOR]

Half‐graben basins bounded by border faults typify early‐stage continental rifts. Deciphering the role that intra‐rift faults play in rift basin development is challenging as patterns of early‐stage faulting are commonly overprinted by subsequent deformation; yet the characterization of these faults is crucial to understand the fundamental controls on their evolution, their contribution to rift opening, and to assess their seismic hazard. By integrating multiple offshore seismic reflection data sets with age‐dated drill core, late‐Quaternary and cumulative faulting patterns are characterized in the Central and South Basins of the Malawi (Nyasa) Rift, an active, early‐stage rift system. Almost all intra‐rift faults offset a late‐Quaternary lake lowstand surface, suggesting they are active and should be considered in hazard assessments. Fault throw profiles reveal sawtooth patterns indicating segmented slip histories. Observed extension on intra‐rift faults is approximately twice that predicted from hanging wall flexure of the border fault, suggesting that intra‐rift faults accommodate a proportion of the regional extension. Cumulative and late‐Quaternary throws on intra‐rift faults are correlated with throw measured on the border fault in the Central Basin, whereas an anticorrelation is observed in the South Basin. Viewed in a regional context, these differences do not relate solely to the proposed southward younging of the rift. Instead, it is inferred that the distribution of extension is also influenced by variations in lithospheric structure and crustal heterogeneities that are documented along the rift axis. Key Points: We carried out a detailed fault analysis of the Malawi (Nyasa) Rift integrating drill core and seismic reflection data65% and 49% of the observed extension on intra‐rift faults in the Central and South Basins is explained by regional tectonic extensionSpatio‐temporal patterns of throw indicate the migration of extension onto intra‐rift faults may be ongoing in the Central Basin [ABSTRACT FROM AUTHOR]

In order to avoid the waste of resources and reserves caused by excessive width of waterproof coal pillar, the method combining theoretical analysis and Flac3D numerical simulation is used to theoretically calculate the width of coal pillars along the floor and along the seam of a F14 high angle normal fault in a mining face, and the mechanical model for fault layer activation is established and analyzed. In order to optimize the width of coal pillar, the fault zone and the top of Ordovician limestone aquifer are transformed by grouting through the construction of ground area treatment. The results show that the F14 high-angle normal fault does not conduct (contain) water, but there is a possibility of fault activation. With the continuous advance of the working face, activation occurs in the fault zone. When the width of the coal pillar is less than 40m, cracks in the fracture zone of F14 fault continue to develop and finally connect with each other to form a good water diversion channel. The Ordovician limestone water in the lower wall of the waterproof fault on the roof and floor of the coal seam rises along the fault fracture zone, threatening the safe mining of the working face. Meanwhile, the theoretical formula is verified, and the width of the waterproof coal pillar is initially determined to be 40 m. The grouting transformation of the fault zone and the top of the Ordovician limestone has improved the integrity of the fault water barrier and relieved the threat of floor water damage to the working face during mining. It is considered that F14 is feasible to liberate the fault waterproof coal pillar. The research results have important reference significance for the liberation of coal resources in the hanging wall working face of high angle normal faults, avoiding waste of resource reserves, improving economic benefits and mining efficiency in mining areas, and provide countermeasures for the tension in coal mine production areas. [ABSTRACT FROM AUTHOR]

The factors that control the spatial variation of the topological characteristics of normal fault networks at the rift‐scale are poorly understood. Here, we use 3D seismic reflection data from the northern North Sea to investigate the spatial variation of the geometry, topology, and strain heterogeneity of the Late Jurassic normal fault network along the rift margin. Our results show that fault orientation varies spatially along the rift margin. Normal faults within fault blocks that are adjacent to the North Viking Graben exhibits dominant N‐S and NE‐SW strikes that are sub‐parallel to the graben axis and associated step‐over, whereas in fault blocks farther from the graben, there is a dominant NW‐SE strike. Furthermore, we identify two broad topological domains within the fault network: (a) dominated by isolated nodes, partially connected branches, and low fault connectivity, and (b) dominated by abutting nodes, fully connected branches, and moderate to high fault connectivity. These topological domains correlate with previous sub‐division of the rift margin in the northern North Sea into platform and sub‐platform structural domains, respectively. There is also a positive correlation between the spatial variability of the fault orientations and intensity, with the fault network connectivity, highlighting the relationship between normal fault geometry and topology. We conclude that the across and along‐strike variation in strain, presence of pre‐existing structures, and accommodation zone‐related deformation are key factors influencing the spatial variation of fault network properties at the rift scale. Key Points: The relative amount of strain, pre‐existing structures and rift accommodation zones influence the spatial variation of fault network topology at the rift‐scaleThe connectivity of normal fault network is largely dependent on the fault network geometry, that is, the combination of the orientation and intensity of the faultsTopological analysis of rift fault network provides a new, but complimentary way to characterize and distinguish large‐scale structural domains in rift systems [ABSTRACT FROM AUTHOR]

We present seismological and geological interpretations of the weak earthquake that occurred on April 6th, 2022 with epicenter between Šalková (suburb of Banská Bystrica) and Slovenská Ľupča. The local magnitude of the event was ML = 2.1. The earthquake was macroseismically observed in 21 localities (101 reports) on the territory of Slovakia with epicentral intensity 4° EMS-98. The estimated focal mechanism indicates a normal fault in approximately E-W direction. This favours the theory of an extension regime in the Čertovica tectonic zone.

The mechanism of the presence of the Sukadana basalt in the back arc of Sumatra is still an enigma, especially since the Sukadana basalt has a wide coverage area in Sumatra Island and even the Sunda Arc. In this study, we used the published research data as the main contributor to an in-depth analysis to determine the mechanism of the presence of Sukadana basalt in the back arc. This study is supported by other studies from different regions around the world. These strengthen our conclusion that the emergence of Sukadana basalt on the surface is controlled by extensional deformations associated with the northwest-southeast-trending normal fault, which are formed by the mechanism of gravitational subsidence due to the movement of the Sumatra fault. In this study we suppose that the Nishimura fracture is a sinistral strike-slip fault as it is consistent with the Riedel shear model.

Reliable reconstructions of paleoseismicity are useful for understanding, and mitigating, seismic hazard risks. In this study, we apply cosmogenic 36Cl exposure-age dating and concentrations of rare-earth elements and yttrium (REY) to unravelling the paleoseismic history of the Sparta fault, Greece, which is a range-bounding normal fault developed in limestone. Modeling of 36Cl concentrations along two vertical profiles on the Sparta Fault indicates a clustering of four earthquakes within a 1.5 kyr period that culminated with the 464 B.C.E. event that devastated Spartan society. Cumulative uplift was as high as 2.8 mm yr-1 during that period, compared with ~0.6-0.9 mm a-1 over the preceding 2.7-4.4 kyr. Because earthquake activity may shift between faults in extensional settings, a large magnitude earthquake is not necessarily indicated as being overdue by the present ~2.5 kyr quiescent period. More generally, accurate identification of individual earthquakes is presently constrained by spatial variations in 36Cl concentration profiles that reflect neither exposure duration nor imprints of former soil profiles. In cases where this is attributable to mineralogical variations, such as in the Sparta fault scarp, present chemical preparation techniques for AMS measurement of 36Cl may insufficiently account for those variations. The Sparta fault scarp is composed of fault breccia, which contains quartz and clay-lined pores, in addition to host rock-derived clasts of calcite and microcrystalline calcite cement. The exchange of REY between the hanging wall colluvium and the fault scarp calcite, which has been applied to the study of paleoseismicity on other limestone normal faults, is overwhelmed on this fault scarp by REY attached to the breccia pore clays. Holocene earthquakes and their magnitudes, inferred from fault slip lengths, therefore cannot be inferred from REY data for impure limestone faults such as the Sparta fault but, rather, these data may indicate processes of fault evolution in the Earth's near surface. [ABSTRACT FROM AUTHOR]

The mechanism of rupture propagation is fundamental to understanding the damage to structures within the fault zones. However, the traditional logarithmic spiral model could not describe some normal fault ruptures of physical tests. Therefore, this study conducted six centrifuge tests to give new insights into normal fault rupture propagation in the sand. The tests simulated normal faulting with dip angles of 60° in the free-filed condition, designed with different relative densities of sand and thicknesses of the overlying soil. The rupture propagation process and effects of relative density and soil thickness were discussed. The mechanism of normal rupture propagation in the sand was summarized, based on the test results. It is observed that two outcropping ruptures develop during normal faulting. The first one is a logarithmic spiral, with a surface angle of 45° + ψmax/2. However, its direction angle at the fault tip disagrees with the logarithmic spiral model. The second outcropping rupture experiences a combined trace due to the reduction in the dilation angle during faulting. The lower part follows a logarithmic spiral. The upper part propagates as a straight trace with an angle of 45° + φmax/2 when the dilation angle falls to the critical state. A slope forms on the ground surface, the angle of which is consistent with φres. [ABSTRACT FROM AUTHOR]

Transfer zones are structural areas of faults interactions where fault motion or displacement can be transferred from one fault to another, regional strain maintains laterally constant. Transfer zones are widely developed in rift basins and have significance on hydrocarbon accumulation. In this review article, we attempt to summarize recent advances on the types, distance-displacement curves, evolutionary stages and controlling factors of transfer zones in rift basins and their effects on sedimentary systems, reservoir properties, trap formation and hydrocarbon migration. The formation of transfer zones is genetically related to the segmented growth of normal faults. Depending on the degree of interaction between these normal faults, transfer zones in rift basins could be divided into two types: soft-linked and hard-linked, which are further subdivided into transfer slope, oblique anticline, horst and transfer fault based on the combination patterns of normal faults. In general, the development of transfer zones experiences several stages including isolated normal faulting, transfer slope forming, complicating and breaking. During the interaction and growth of segmented normal faults, stress-strain and spatial array of faults, pre-existing basement structures, and mechanical conditions of rocks have a great influence on the location and development processes of transfer zones. A transfer zone is commonly considered as a pathway for conveying sediments from provenance to basin, and it hence exerts an essential control on the distribution of sandbodies. In addition, transfer zone is the area where stresses are concentrated, which facilitates the formation of various types of structural traps, and it is also a favorable conduit for hydrocarbon migration. Consequently, there exists great hydrocarbon potentials in transfer zones to which more attention should be given. [ABSTRACT FROM AUTHOR]

Confined water inrush caused by fault activation induced by coal mining under high in-situ stress is one of the main forms of water damage in deep mining. Reserving fault waterproof coal pillar is still the most important method to prevent fault activation and water diversion. We take F22 high angle normal fault in Qianyingzi Coal Mine as a typical example, based on the existing drilling, geophysical and roadway exploration data, the specific hydro-geological and engineering geological conditions of the coal mine, and according to the field test data, the finite difference numerical analysis method was used to study the width of the waterproof coal pillar under the full mining of the W3221 working face near F22 fault of Qianyingzi Coal Mine; at the same time, the width of the F22 fault waterproof coal pillar was calculated and verified according to the theoretical formula. The study shows that when the coal pillar width is less than 40 m, the stress and displacement of the fault zone have changed significantly, and the plastic zone in the fault zone has communicated with the water-conducting fracture zone of the coal seam roof. The comprehensive analysis of numerical simulation and theoretical calculation results show that the waterproof coal pillar with a width of 40 m can effectively prevent the fault activation and ensure the safe production of the working face.

Abstract Oil and gas pipelines that go through an active normal fault often deform largely and cause serious disasters. On the basis of the beam theory of the elastic foundation and assuming a shape function for the deformed pipeline, a new analytical method is proposed to calculate the pipeline strain under a normal fault. The length of the deformed pipeline is calculated by using a simplified structural mechanical model. Moreover, a three‐dimensional solid finite element model (3D FEM) is developed to calculate the pipeline strain under different working conditions. The developed analytical solution and the numerical results of 3D FEM are compared with the results of the two traditional methods (the dissipated energy method and the Karamitros method). The strain development law predicted by the proposed method and the 3D FEM is in good agreement with that of the dissipated energy method and the Karamitros method. Compared with the existing models, the new analytical method is simpler and more efficient.

Purpose – Large displacement misalignment under the action of active faults can cause complex three-dimensional deformation in subway tunnels, resulting in severe damage, distortion and misalignment. There is no developed system of fortification and related codes to follow. There are scientific problems and technical challenges in this field that have never been encountered in past research and practices. Design/methodology/approach – This paper adopted a self-designed large-scale active fault dislocation simulation loading system to conduct a similar model test of the tunnel under active fault dislocation based on the open-cut tunnel project of the Urumqi Rail Transit Line 2, which passes through the Jiujiawan normal fault. The test simulated the subway tunnel passing through the normal fault, which is inclined at 60°. This research compared and analyzed the differences in mechanical behavior between two types of lining section: the open-cut double-line box tunnel and the modified double-line box arch tunnel. The structural response and failure characteristics of the open-cut segmented lining of the tunnel under the stick-slip part of the normal fault were studied. Findings – The results indicated that the double-line box arch tunnel improved the shear and longitudinal bending performance. Longitudinal cracks were mainly distributed in the baseplate, wall foot and arch foot, and the crack position was basically consistent with the longitudinal distribution of surrounding rock pressure. This indicated that the longitudinal cracks were due to the large local load of the cross-section of the structure, leading to an excessive local bending moment of the structure, which resulted in large eccentric failure of the lining and formation of longitudinal cracks. Compared with the ordinary box section tunnel, the improved double-line box arch tunnel significantly reduced the destroyed and damage areas of the hanging wall and footwall. The damage area and crack length were reduced by 39 and 59.3%, respectively. This indicates that the improved double-line box arch tunnel had good anti-sliding performance. Originality/value – This paper adopted a self-designed large-scale active fault dislocation simulation loading system to conduct a similar model test of the tunnel under active fault dislocation. This system increased the similarity ratio of the test model, improved the dislocation loading rate and optimized the simulation scheme of the segmented flexible lining and other key factors affecting the test. It is of great scientific significance and engineering value to investigate the structure of subway tunnels under active fault misalignment, to study its force characteristics and damage modes, and to provide a technical reserve for the design and construction of subway tunnels through active faults.

Sedimentary breccias deposited on a talus slope during extension at the front of a normal fault or at the base of a slope are related to the creation of substantial topography. The architecture of talus slopes resulting from exhumation during extension is different from that of rock cliffs without deformation. In this work, we run several analogue models, with or without extension, in order to analyse the external geometry and internal organization of sedimentary breccias and their evolution in time and space. This temporal organization of the sand layers in the experiments shows that normal unroofing sequences are characteristic of progressive exhumation and continuous deformation during extension, whereas reverse unroofing is related to cliff destruction without vertical movement. In the experiment with wet layers of sand, the blocks that resulted from the aggregates of sand grains are generally deposited farther away than single sand grains and are located at the base of the slope; this is one of the main characteristics of rockfalls. The analogue results are compared to natural examples.

The existing research on the rock burst risk of faults under different conditions is mostly carried out around the footwall mining or single fault form. The comparative research on the rock burst risk of hanging wall mining of different faults is seldom involved. In order to solve the above problems, the 12220 working face of Gengcun Coal Mine in Yima, Henan is taken as the research background. The rock burst risk of mining in hanging wall of normal and reverse faults is analyzed by means of theoretical analysis, numerical simulation and field monitoring. The mechanical model of mining in the hanging wall of normal and reverse faults is established. The mechanical condition of shear slip on the fault is obtained by analyzing the stress of fault rock. The results of the theoretical analysis show that the occurrence of shear slip is closely related to such factors as fault dip angle, internal friction angle of fault and fault surface force on rock block during hanging wall mining of normal and reverse faults. The closer the working face is to the fault, the greater the risk of shear slip. The numerical simulation of the mining process in the hanging wall of normal and reverse faults is carried out, and the normal stress, shear stress and slippage of the fault plane are analyzed. The results show that in the mining process of the working face, when the distance between the working face and the fault is less than 40 m, the risk of shear slip and rock burst increases gradually. When the distance from the fault is 10 m, the risk is the greatest. The most likely position for shear slip is the coal seam roof and coal seam of the fault plane. The influence degree of the coal seam floor is obviously less than that of the roof. The type of fault has a certain impact on the rock burst risk. The rock burst risk of reverse fault mining is higher than that of normal fault. Microseismic monitoring of rock burst risk is carried out on the 12220 working face. The results show that when the working face is less than 20 m from the fault, the microseismic events are frequent and the rock burst risk is high. The results are consistent with the numerical simulation results, which verifies the rationality of the numerical simulation analysis.

Karya Murni is one of the areas in the northern arm of Sulawesi that has been tectonically influenced. Tectonic processes have implications for the formation of rocks and geological features that have the potential to be developed into geodiversity sites. The development of geological features as a geodiversity site in aspiring geopark Gorontalo can protect valuable geological features from frequent degradation. This research aims to analyze and conduct quantitative assessments of geological diversity in Karya Murni, Gorontalo. The research method used is field observation, laboratory analysis, and geodiversity assessment. Field observations included observing landform, collecting rock samples, and measuring geological structures. Field observations were also carried out to observe aspects of the geodiversity assessment which included science, education, tourism, and risk degradation. Laboratory analysis consists of geomorphological analysis, petrographic analysis, and geological structure data analysis. Geodiversity assessment uses the Geological Survey Center of Indonesia assessment. The results suggest that the geomorphology of the study area can be divided into four geomorphic units - the volcanic hills, denudational hills, Karst hills, and fluvial plain units. The stratigraphy of the research area is divided into four units from the age of the early Eocene to the Holocene - the andesite lava, volcanic breccia, reef limestone, and alluvial deposit units. The geological structure of the study area is a trending northeast --southwest to northwest--southeast. Active faults at the location of the study area consist of the Apitalawu normal fault. At recent states, generally geosites of the Karya Murni have moderate scientific values, the low educational and touristic values and high risk of degradation. The geodiversity potential of the research area can be utilized for further research and education. [ABSTRACT FROM AUTHOR]

Fissures and faults provide insight into how plate separation is accommodated by magmatism and brittle deformation during crustal accretion. Although fissure and fault geometry can be used to quantify the spreading process at mid‐ocean ridges, accurate measurements are rare due to insufficiently detailed mapping data. Here, fissures and faults at the fast‐spreading 9°50′N segment of the East Pacific Rise were mapped using bathymetric data collected at 1‐m horizontal resolution by autonomous underwater vehicle Sentry. Fault dip estimates from the bathymetric data were calibrated using co‐registered near‐bottom imagery and depth transects acquired by remotely operated vehicle Jason. Fissures are classified as either eruptive or non‐eruptive (i.e., cracks). Tectonic strain estimated from corrected fault heaves suggests that faulting plays a negligible role in the plate separation on crust younger than 72 kyr (<4 km from the ridge axis). Pre‐ and post‐eruption surveys show that most fissures were reactivated during the eruptions in 2005–2006. Variable eruptive fissure geometry could be explained by the frequency with which each fissure is reactivated and partially infilled. Fissure swarms and lava plateaus in low‐relief areas >2 km from the ridge are spatially associated with off‐axis lower‐crustal magma lenses identified in multichannel seismic data. Deep, closely spaced fissures overlie a relatively shallow portion of the axial magma lens. The width of on‐axis fissures and inferred subsurface dike geometry imply a ∼9‐year long diking recurrence interval to fully accommodate plate spreading, which is broadly consistent with cycle intervals obtained from estimates of melt extraction rates, eruption volumes, and spreading rate. Plain Language Summary: New oceanic crust is created by seafloor spreading at mid‐ocean ridges, where lava erupts as the tectonic plates spread apart. Plate separation is accommodated by a combination of slip along dipping faults and the opening of magma‐filled cracks, called dikes. We present bathymetric and profile mapping data collected from near the seafloor on a volcanically active portion of the East Pacific Rise near 9°50′N. The data show faults and fissures (i.e., open cracks) in remarkable detail, with meter‐scale resolution. A total of 707 fissures and 42 faults were identified and measured, suggesting that the amount of plate separation accommodated by faulting is minimal compared to that by dike intrusion causing open cracks. About one‐third of the fissures mapped are located within the region covered by the most recent eruptions in 2005–2006, and most of these fissures seem to have been reactivated from previous eruptions. Based on measurements of fissure width, we estimate that the interval between diking events is ∼9 years, which agrees with previous independent estimates. The analysis in this study reveals the relative importance of faults and fissures in seafloor spreading, and in the magmatic cycles that continuously re‐pave the ocean floor. Key Points: >700 fissures mapped at 1‐m bathymetric resolution at 9°50′N East Pacific Rise, most of which were active during the 2005–2006 eruptionsFault slip and crack opening accommodate <0.3% of plate separation, indicating the dominant role of diking at fast‐spreading ridgesFissures and lava flow located >2 km from the ridge axis are spatially associated with off‐axis lower crustal off‐axis magma lens [ABSTRACT FROM AUTHOR]

The Calamocha fault is an 18-km-long, NNW–SSE striking pure normal fault that moves down the northern sector of the Jiloca graben with respect to the Neogene infill of the Calatayud basin (central Iberian Chain). Its structure and kinematics are characterized by means of detailed geological mapping, morphotectonic analysis and data recording at the outcrop scale. The Calamocha fault represents the inversion of a previous contractional fault zone under the recent tensional stress field (WSW–ENE trending σ3 trajectories). The extensional activity started during the Late Pliocene (ca. 3.8 Ma), accumulating a maximum net slip of 190–230 m (long-term slip rate of 0.05–0.06 mm/a). The palaeoseismological study of three artificial exposures near Calamocha town evidenced recurrent slip during the Late Pleistocene, which proves its active character. Analysis of faulted clastic alluvial units, dated by means of optically stimulated luminescence (OSL), reveals at least eight slip events since 145.9 ± 9.1 ka, the last one being younger than 13.8 ± 0.9 ka. Only a few events represent visible accumulated displacement on the main synthetic rupture surfaces; this allows a rough estimate of the short-term slip rate (during the Late Pleistocene) of about 0.1 mm/a, faster than the long-term rate. The Calamocha fault could potentially produce a characteristic earthquake (in the sense of Schwartz and Coppersmith, J Geophys Res 89:5681–5698, 1984) with moment magnitude Mw ≈ 6.7 ± 0.3 (Mw ≈ 6.9 ± 0.3 in a scenario of activation of the whole Calamocha–Daroca fault zone), average coseismic displacement of 0.5–1.3 m and average recurrence period under 15 ka. [ABSTRACT FROM AUTHOR]

Abstract Fissures and faults provide insight into how plate separation is accommodated by magmatism and brittle deformation during crustal accretion. Although fissure and fault geometry can be used to quantify the spreading process at mid‐ocean ridges, accurate measurements are rare due to insufficiently detailed mapping data. Here, fissures and faults at the fast‐spreading 9°50′N segment of the East Pacific Rise were mapped using bathymetric data collected at 1‐m horizontal resolution by autonomous underwater vehicle Sentry. Fault dip estimates from the bathymetric data were calibrated using co‐registered near‐bottom imagery and depth transects acquired by remotely operated vehicle Jason. Fissures are classified as either eruptive or non‐eruptive (i.e., cracks). Tectonic strain estimated from corrected fault heaves suggests that faulting plays a negligible role in the plate separation on crust younger than 72 kyr (2 km from the ridge are spatially associated with off‐axis lower‐crustal magma lenses identified in multichannel seismic data. Deep, closely spaced fissures overlie a relatively shallow portion of the axial magma lens. The width of on‐axis fissures and inferred subsurface dike geometry imply a ∼9‐year long diking recurrence interval to fully accommodate plate spreading, which is broadly consistent with cycle intervals obtained from estimates of melt extraction rates, eruption volumes, and spreading rate.

Oil and gas pipelines that go through an active normal fault often deform largely and cause serious disasters. On the basis of the beam theory of the elastic foundation and assuming a shape function for the deformed pipeline, a new analytical method is proposed to calculate the pipeline strain under a normal fault. The length of the deformed pipeline is calculated by using a simplified structural mechanical model. Moreover, a three‐dimensional solid finite element model (3D FEM) is developed to calculate the pipeline strain under different working conditions. The developed analytical solution and the numerical results of 3D FEM are compared with the results of the two traditional methods (the dissipated energy method and the Karamitros method). The strain development law predicted by the proposed method and the 3D FEM is in good agreement with that of the dissipated energy method and the Karamitros method. Compared with the existing models, the new analytical method is simpler and more efficient. [ABSTRACT FROM AUTHOR]

Long paleoearthquake series are crucial for understanding the recurrence patterns of active faults and evaluating the seismic hazards of faults. In this study, the first semiquantitative evaluation of paleoearthquake events from trenches was applied to normal faults, and classification criteria for identifying paleoearthquakes in trenches on normal faults are proposed to demonstrate the feasibility of semiquantitative evaluations of paleoearthquake events on normal faults. In this study, 72 paleoearthquake trench sites on normal faults around the world were analyzed, and the main indicators for identifying paleoearthquakes on normal faults include the presence of vertical offset (VO), collapse wedge (CW), fissure (FIS), buried paleosol (BP), angular unconformity (AU), upward termination (UT), and sand liquefaction (LF) features. To describe and apply this semiquantitative evaluation method for paleoearthquake events on normal faults, 33 trenches for paleoearthquakes on a fault system in the northern margin of the Hetao Basin were comprehensively analyzed to determine Holocene paleoearthquake events on the Sertengshan, Wulashan, and Daqingshan piedmont faults, and the reliability of paleoearthquake events is discussed. The integrity of the paleoearthquake events obtained was tested by the displacement limit method. The Holocene paleoearthquake recurrence on the three faults was quasiperiodic; the coefficients of variation (COVs) were 0.44, 0.58, and 0.4. Plain Language Summary: In this study, 72 paleoearthquake trench sites on normal faults around the world are analyzed, and summarized the main indicators for identifying paleoearthquakes on normal faults. Classification criteria for identifying paleoearthquakes in trenches on normal faults are proposed. Using the faults of the northern margin of the Hetao Basin as an example, this study described a semiquantitative evaluation method for normal fault paleoearthquake events, and discussed the reliability of paleoearthquake events. The integrity of the paleoearthquake events obtained was tested by the displacement limit method. Combining with studies on the reliability and integrity of paleoearthquake events, we argue that it is feasible to apply semiquantitative evaluations of paleoearthquake events from trenches to paleoearthquake research on normal faults. Key Points: Semiquantitative evaluation of paleoearthquake identification from trenches to normal faults is applied for the first timeClassification criteria are proposed for identifying paleoearthquakes in trenches on normal faultsThis study demonstrates the feasibility of semiquantitative evaluation of paleoearthquake events on normal faults [ABSTRACT FROM AUTHOR]

Large magnitude (Mw ∼ ≥6) earthquakes in extensional settings are often associated with simultaneous rupture of multiple normal faults as a result of static and/or dynamic stress transfer. Here, we report details of the coseismic breaching of a previously unrecognized large‐scale fault relay zone in central Greece, through three successive normal fault earthquakes of moderate magnitude (Mw 5.7–6.3) that occurred over a period of ∼10 days in March 2021. Specifically, joint analysis of InSAR, GNSS and seismological data, coupled with detailed field and digital fault mapping, reveals that the Tyrnavos Earthquake Sequence (TES) was accommodated at the northern end of a ∼100 km wide transfer structure, by faults largely unbroken during the Holocene. By contrast, the southern section of this relay zone appears to have accrued significant slip during Holocene. InSAR‐derived displacements agree with the loci of eight subtle, previously undetected, faults that accommodated coseismic and/or syn‐seismic normal fault slip during the TES. Kinematic modeling coupled with fault mapping suggests that all involved faults are interconnected at depth, with their conjugate fault‐intersections acting largely as barriers to coseismic rupture propagation. We also find that the TES mainshocks were characterized by unusually high (>6 MPa) stress‐drop values that scale inversely with rupture length and earthquake magnitude. These findings, collectively suggest that the TES propagated north‐westward to rupture increasingly stronger asperities at fault intersections, transferring slip between the tips of a well‐established, but previously unrecognized, relay structure. Fault relay zones may be prone to high stress‐drop earthquakes and associated elevated seismic hazard. Key Points: Revised fault mapping reveals that the Tyrnavos Earthquake Sequence ruptured the tip of a large‐scale relay zone that remained unbreached during the HoloceneInSAR‐derived coseismic and syn‐seismic fault slip in good agreement with the location of subtle, previously unmapped, geological faultsUnusually high stress‐drop values likely suggest that rupture was arrested by strong asperities at normal fault intersections [ABSTRACT FROM AUTHOR]

Earthquake surface deformation provides key constraints on the geometry, kinematics, and displacements of fault rupture. However, deriving these characteristics from past earthquakes is complicated by insufficient knowledge of the pre‐event landscape and its post‐event modification. The 1987 Mw 6.5 Edgecumbe earthquake in the northern Taupō volcanic zone (TVZ) in New Zealand represents a moderate‐magnitude earthquake with distributed surface rupture that occurred before widespread high‐resolution topographic data were available. We use historical aerial photos to build pre‐ and post‐earthquake digital surface models (DSMs) using structure‐from‐motion techniques. We measured discrete and distributed deformation from differenced DSMs and compared the effectiveness of the technique to traditional field‐ and lidar‐based studies. We identified most fault traces recognized by 1987 field mapping, mapped newly identified traces, and made dense remote slip measurements with a vertical separation resolution of ∼0.3 m. Our maximum and average vertical separation measurements on the Edgecumbe fault trace (2.5 ± 0.3 and 1.2 m, respectively), are similar to field‐based values of 2.4 and 1.1 m, respectively. Importantly, this technique can discern between new and pre‐existing fault scarps better than field techniques or post‐earthquake lidar‐based measurements alone. Our surface displacement results are used to refine subsurface fault geometries and slip distributions at depth, which are further used to investigate potential magmatic‐tectonic stress interactions in the northern TVZ. Our results suggest the Edgecumbe fault dips more gently at depth than at the surface, hosted shallow slip in 1987, and may be advanced toward failure by interactions with nearby magma bodies. Plain Language Summary: Understanding earthquake behavior relies heavily on information about how past earthquakes changed the landscape. Detailed information about the surface topography before the earthquake is often limited, creating challenges for accurately measuring earthquake surface deformation. Aerial photos are widely available and can be used to create 3D digital surface models in places where other topographic information is lacking. We use historical aerial photos to make 3D datasets of the surface topography before and after the 1987 Edgecumbe earthquake in New Zealand. We calculated the difference between the two 3D datasets to identify and measure how the earthquake changed the landscape, and compared our results to previous measurements. We found that this method generally works as well as field methods for identifying and measuring fault movement, and has some advantages over other techniques. In particular, this approach can separate deformation from individual earthquakes, which had previously been a challenge. The results refine our understanding of the faults below the surface, provide insight into the earthquake's relationship to surrounding faults and volcanic systems, and allow us to better characterize seismic hazard both here and in other similar geologic settings. Key Points: Historical aerial photos can be used to generate pre‐ and post‐earthquake digital surface models for measuring displacementThis method performs at least as well as field surveys, and better captures single‐event displacements to constrain earthquake behaviorThe Edgecumbe earthquake is important for understanding low dip‐angle normal fault ruptures and possibly magma‐tectonic interactions [ABSTRACT FROM AUTHOR]

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Increasing displacement along an isolated fault is generally associated with fault propagation within the host rock. This propagation is controlled by several factors, including host-rock lithology, tectonic context and the presence of preexisting structures. Consequently, fault propagation is rarely linear and continuous, instead often alternating between periods of propagation and arrest, or propagation locking. We present structural data collected in a field at the terminal tip of the Argence Fault, one of the regional normal faults in the northern part of the Aquitaine Basin. At the outcrop, the fault cuts a heterogeneously layered sequence of limestones, marls and clays. We observed a well-exposed tip of this fault, and analyzed the deformation patterns. This analysis provided insights into the processes involved in the formation of fault zones, the fault damage zone in particular, and the effects of contrasting mechanical properties on modes of fault growth.

The reasonable effective extraction radius of borehole is the key to ensure gas extraction effect. However, the research of effective extraction radius mainly focuses on the measurement method of effective extraction radius of borehole, and there is a lack of research on the effective extraction radius of borehole under special geological conditions of normal fault. Taking a coal working face in Guizhou as the engineering background, the fluid-solid coupling model is established, and the variation law of effective extraction radius of bedding borehole without fault impact is analyzed by means of mutual verification between numerical simulation and borehole gas extraction method. The results show that when the gas is extracted for 120 days, the effective extraction radius of the numerical simulation is 3.10 m, and that of the field test is 2.93 m. The field results are basically consistent with the numerical simulation results, which verifies the reliability of the fluid-solid coupling model. By using multi-physics field coupling simulation software, the variation law of effective extraction radius of bedding borehole under the impact of normal fault is analyzed. The results show that within a certain extraction time range, when the borehole is at a certain distance from the normal fault, the gas pressure curve will have a hump-like distribution, and the peak interval is about 3.5 m. The effective extraction radius of the borehole near the normal fault increases with the increase of the distance from the fault. The impact of the normal fault on the effective extraction radius of the borehole is within 70 m from the fault. Combined with the analysis results under the impact of normal faults, the spacing of gas drainage boreholes near the normal fault is arranged in sections under the premise of ensuring the extraction effect and not prolonging the extraction time. Within 30 m from the fault, the boreholes are densely arranged, and the spacing between the boreholes should not be greater than the effective extraction radius (1.83 m) when the distance from the fault is 10 m. Within the range of 30-70 m from the fault, under the condition of ensuring safety, the spacing of boreholes can be appropriately increased. After 70 m from the fault, the spacing can be gradually restored to the borehole spacing layout of bedding boreholes without the impact of the normal fault.