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The Superstition Hills Fault (SHF) exhibits a rich spectrum of slip modes, including M 6+ earthquakes, afterslip, quasi‐steady creep, and both triggered and spontaneous slow slip events (SSEs). Following 13 years of quiescence, creepmeters recorded 25 mm of slip during 16–19 May 2023. Additional sub‐events brought the total slip to 41 mm. The event nucleated on the northern SHF in early‐May and propagated bi‐laterally at rates on the order of kilometers per day. Surface offsets reveal a bi‐modal slip distribution, with slip on the northern section of the fault being less localized and lower amplitude compared to the southern section. Kinematic slip models confirm systematic variations in the slip distribution along‐strike and with depth and suggest that slip is largely confined to the shallow sedimentary layer. Observations and models of the 2023 SSE bear a strong similarity to previous slip episodes in 1999, 2006, and 2010, suggesting a characteristic behavior. Plain Language Summary: Studying the mechanical properties and behavior of faults is essential for understanding earthquake ruptures. In this study, we investigate a recent slip event on the Superstition Hills Fault (SHF), which has a well‐documented record of slip. A notable aspect of the SHF is that it periodically undergoes "slow slip events" (SSEs), where the fault slips and releases energy without any accompanied ground shaking. During May‐July 2023, the SHF experienced a major SSE for the first time in 13 years. Our analysis shows that it was the largest documented SSE on the SHF and released equivalent energy to a magnitude 4.5 earthquake. We also find that the spatial pattern of fault slip is very similar to several previous slip events in 1999, 2006, and 2010, suggesting that the SHF has a tendency to slip in a characteristic manner. Key Points: We document a recent spontaneous slow slip event (SSE) on the Superstition Hills Fault using creepmeter, Interferometric Synthetic Aperture Radar, Global Navigation Satellite System, and field measurementsOver 41 mm of slip occurred from mid‐May to mid‐July 2023, with moment release corresponding to a Mw 4.5 earthquakeThe kinematics of the 2023 event are remarkably similar to several previous SSEs, suggesting a characteristic rupture process [ABSTRACT FROM AUTHOR]

Paying attention to the relationship between EIA signatures and earthquakes can be useful to further understand the earthquake anomalies and seismo-ionospheric coupling mechanism. Based on the GIM TEC data, the EIA north crest signature in the south Asia region was investigated for 92 M ≥ 6.0 earthquakes from 1999 to 2022. A running mean method was utilized to extract the anomalies potentially associated with earthquakes. It was found that before the strong earthquakes, the EIA north crest significantly moves equatorward, and the formation time of the crest appears earlier than that in normal days. The TEC strength of EIA north crest can both increase or decrease prior to earthquakes. The results in this study further imply that the abnormal electric field formed around the epicenter is potential the main channel of Lithosphere-Atmosphere-Ionosphere Coupling (LAIC) mechanisms during the earthquake preparation period. [ABSTRACT FROM AUTHOR]

On September 17th and 18th, 2022, shallow earthquakes with magnitudes of 6.6 (ML) and 6.8 (ML) occurred in the eastern Taiwan Longitudinal Valley, which marks the collision zone between the Philippine Sea plate and the Eurasian plate, and led to noticeable surface deformation and ruptures within 70 km. This study primarily focuses on the southernmost section of the rupture zone—the Pingting Terrace. Surface rupture locations and behaviors correspond to changes in topography, providing mutual confirmation that the deformation behavior of Pingting Terrace is complex. Based on the distribution of surface ruptures and topography changes, this study roughly divides the Pingting Terrace into northern and southern segments, using the central concave feature as a boundary. The Riedel shear model analysis results show that the principal shear directions in the northern and southern segments are N–S trending and azimuth 20°, respectively. The maximum principal stress orientations are around 135° for the northern and 155° for the southern segments. These findings align with the fault mechanical investigation of the Lichi Mélange in the northern Muken River area of the Pingting Terrace. This suggests spatial changes in shear zone orientations within the Lichi Mélange, which contribute to developing pressure ridges due to transpressional forces. As a result, the Pingting Terrace experiences rapid uplift, causing the Luliao River to migrate southward into the Beinan River, while the eastern Beinan River turns to the eastward edge of the Pingting Terrace. Key points: Co-seismic surface rupture analysis using Riedel shear model. Flower structure of the Pingting Terrace. Relationship between the River channel change and the tectonic activity. [ABSTRACT FROM AUTHOR]

Two closely timed moderate-sized earthquakes (e.g., the ML 6.6 Guanshan and ML 6.8 Chihshang earthquakes) occurred in eastern Taiwan on 17–18 September 2002. To understand the rupture relationship between the two earthquakes, we used a teleseismic P-wave inversion and rupture directivity analysis to investigate the source parameters of the ML 6.6 Guanshan earthquake. The teleseismic P-wave inversion method assumed earthquake rupture to be a single source to determine the focal mechanism, seismic moment, and azimuth-dependent source duration for the Guanshan earthquake. The rupture directivity analysis using the azimuth-dependent source duration showed that the Guanshan earthquake unilaterally ruptured along a west-dipping fault plane (Central Range fault) with a rupture velocity (Vr) of approximately 2.8 km/s from the hypocenter toward the deeper part of the fault. Furthermore, through time-domain deconvolution, the source time function of the Guanshan earthquake approximated an isosceles triangle, which also indicated that the earthquake rupture was relatively simple. Here, we propose a fault-based relationship between the ML 6.6 Guanshan and ML 6.8 Chihshang earthquakes. After the ML 6.6 Guanshan earthquake, the source area was relocked, preventing the Chihshang earthquake from rupturing southward. Instead, it ruptured the fault from south to north. [ABSTRACT FROM AUTHOR]

In 2023, two consecutive earthquakes exceeding a magnitude of 7 occurred in Türkiye, causing severe casualties and economic losses. The damage to critical urban infrastructure and building structures, including highways, railroads, and water supply pipelines, was particularly severe in areas where these structures intersected the seismogenic fault. Critical infrastructure projects that traverse active faults are susceptible to the influence of fault movement, pulse velocity, and ground motions. In this study, we used a unique approach to analyze the acceleration records obtained from the seismic station array (9 strong ground motion stations) located along the East Anatolian Fault (the seismogenic fault of the MW7.8 mainshock of the 2023 Türkiye earthquake doublet). The acceleration records were filtered and integrated to obtain the velocity and displacement time histories. We used the results of an on-site investigation, jointly conducted by China Earthquake Administration and Türkiye's AFAD, to analyze the distribution of PGA, PGV, and PGD recorded by the strong motion array of the East Anatolian Fault. We found that the maximum horizontal PGA in this earthquake was 3.0 g, and the maximum co-seismic surface displacement caused by the East Anatolian Fault rupture was 6.50 m. As the fault rupture propagated southwest, the velocity pulse caused by the directional effect of the rupture increased gradually, with the maximum PGA reaching 162.3 cm/s. We also discussed the seismic safety of critical infrastructure projects traversing active faults, using two case studies of water supply pipelines in Türkiye that were damaged by earthquakes. We used a three-dimensional finite element model of the PE (polyethylene) water pipeline at the Islahiye State Hospital and fault displacement observations obtained through on-site investigation to analyze pipeline failure mechanisms. We further investigated the effect of the fault-crossing angle on seismic safety of a pipeline, based on our analysis and the failure performance of the large-diameter Thames Water pipeline during the 1999 Kocaeli earthquake. The seismic method of buried pipelines crossing the fault was summarized. [ABSTRACT FROM AUTHOR]

The September 26, 2019 Silivri earthquake (MW = 5.8) occurred along the North Anatolian Fault beneath the Marmara Sea and its epicenter was in an identified seismic gap. Coseismic stress calculations demonstrate that the 1999 İzmit earthquake (MW = 7.4) caused stress increase from 0.057 to 0.114 bars at its hypocenter, depending on the various reported rupture parameters. In addition, over 20 years following the 1999 earthquake, and constituting the main difference from previous studies, viscoelastic postseismic stress computations indicate stress increase from 0.081 to 0.135 bars at the hypocenter. In spite of the positive stress transfer, the 2019 earthquake occurred long after the end of the computed aftershock time span (~ 16 years) of the 1999 earthquake. Plots of the seismicity around selected points within the gap also show that the background seismicity level following the 1999 earthquake was reached in 2003. Therefore, it is suggested that the 2019 earthquake was not an aftershock but rather an independent event, and its occurrence was hastened about 4 years due to stress loading. Further analysis of the seismicity between 1978 and 2020 indicates that the b value increased from a range of 1.0–1.1 to 1.6–1.8 till 2002, then progressively decreased to 0.9–1.0, which is consistent with positive stress transfer. The stress increase ranging from 0.19 to 2.52 bars on the segments within the gap brought forward their seismic cycles about 33 and 2 years from east to west, respectively. These additional clock advances in the seismic cycles due to stress load urgently require risk mitigating actions. [ABSTRACT FROM AUTHOR]

We analyze seismicity catalogues and find the periodicity of earthquakes in some regions of the northwest Himalaya. In particular, we identify spatiotemporal patterns in the distributions of earthquake occurrence. Earthquake sequences from 1963 to 2017 and 1991–2017, complete for magnitudes M ≥ 4.3 and M ≥ 3.3, respectively, are used to inspect the spatial b-value variation and hidden periodicities for three different regions. The thrust-dominated tectonic block of the Garhwal–Kumaon Himalaya favours more frequent occurrence of strong (large) earthquakes than the Kangra–Kinnaur sector dominated by nappe tectonics. Accompanied by the well-defined pattern of seismic quiescence-enhancement, the time-evolution periodicities have different behaviour associated with strong earthquakes, namely, the Mw 6.6 Chamoli earthquake of 1999 and Mb = 6.6 Uttarkashi earthquake of 1991. An increase in the amplitude of the periodicity in the period range of ~500 days appears ~0.5 years before the mainshock. The pre- and co-seismic periods of the 2012 earthquake of M 5.1 in the Delhi–Haridwar region highlight a strong high-amplitude periodicity in the period range of ~500–1000 days. This indicates that monitoring time-frequency dynamical spectra in near real-time can serve as a helpful guide in identifying hidden periodicities in earthquake sequences. [ABSTRACT FROM AUTHOR]

In the present study, 1991 Uttarkashi (M 7) and 1999 Chamoli (M 6.6) earthquakes that occurred on October 19, 1991, at 21:23:14 h and March 28, 1999, at 19:05:11 h, respectively, have been simulated using the modified hybrid technique. Hybrid technique is the combination of two existing techniques, i.e., envelope technique and composite source model technique. In the present modified technique, site amplification functions and kappa factor have also been incorporated. The simulated waveforms and their corresponding response and Fourier spectra for each site have been generated. In this study, simulation has been done at 11 and 9 recorded stations of Uttarkashi and Chamoli earthquakes, respectively. Important frequency- and time-domain parameters, i.e., Fourier spectra, response spectra, peak ground acceleration (PGA) and duration at stations, have been estimated and compared with the observed accelerograms. It has been observed that the simulated PGA (231 cm/s2) at the closest distance Bhatwari (22 km) matched with the observed one (248 cm/s2) for the Uttarkashi earthquake. The same has been observed at the nearest most station Gopeshwar (19 km) of the Chamoli earthquake. The simulated PGA (347 cm/s2) for this station has been found well matched with the observed PGA value (352 cm/s2). Similar matching has been observed for other stations also. The present technique is independent of velocity-Q structure of earth's layered model and past events data of small earthquakes. This study brings light on the site effect and high-frequency decay parameter. This study can be very helpful in the estimation of seismic hazard in a specific region and designing earthquake-resistant buildings. [ABSTRACT FROM AUTHOR]

On 23 November 2022, a MW 6.0 earthquake occurred in the direct vicinity of the MW 7.1 Düzce earthquake that ruptured a portion of the North Anatolian Fault in 1999. The Mw 6.0 event was attributed to a small portion of the Karadere fault off the main North Anatolian Fault that did not rupture during the 1999 sequence. We analyze the spatiotemporal evolution of the MW 6.0 Gölyaka–Düzce seismic sequence at various scales and resolve the source properties of the mainshock. Modeling the decade-long evolution of the background seismicity of the Karadere fault employing an Epistemic Type Aftershock Sequence model shows that this fault was almost seismically inactive before 1999, while a progressive increase in seismic activity is observed from 2000 onwards. A newly generated high-resolution seismicity catalog from 1 month before the mainshock until 6 d after was created using artificial-intelligence-aided techniques and shows only a few events occurring within the rupture area within the previous month, no spatiotemporal localization process and a lack of immediate foreshocks preceding the rupture. The aftershock hypocenter distribution suggests the activation of both the Karadere fault, which ruptured in this earthquake, and the Düzce fault that ruptured in 1999. First results on the source parameters and the duration of the first P-wave pulse from the mainshock suggest that the mainshock propagated eastwards, which is in agreement with predictions from a bimaterial interface model. The MW 6.0 Gölyaka–Düzce event represents a good example of an earthquake rupture with damaging potential within a fault zone that is in a relatively early stage of the seismic cycle. [ABSTRACT FROM AUTHOR]

Understanding the kinematic characteristics of the Longitudinal Valley Fault Zone (LVFZ) can help us to better understand the evolution of orogens. The 2022 Mw7.0 Taitung earthquake that occurred in Taiwan provides us with a good opportunity to understand the motion characteristics of the Central Range Fault (CRF) and the strain partitioning pattern within the Longitudinal Valley Fault (LVF). We obtained the coseismic displacement and slip distribution of the 2022 Taiwan earthquake based on the strong-motion and GPS data available. The causative fault of this earthquake is the west-dipping Central Range Fault, which is buried beneath the western boundary of the LVF. The coseismic displacement field exhibits a quadrant distribution pattern, indicating a left-lateral strike-slip mechanism with a maximum displacement exceeding 1.25 m. The joint inversion results show that the size of the main asperity is 40 km × 20 km, and the maximum slip amount of 2.6 m is located at a depth of 10 km, equivalent to an earthquake of Mw7.04. The LVFZ is composed of LVF and CRF, which accommodates nearly half of the oblique convergence rate between the Philippine Sea Plate and the Eurasian Plate. There is a phenomenon of strain partitioning in the southern segment of the Longitudinal Valley Fault Zone. The Central Mountain Range Fault is primarily responsible for accommodating strike-slip motion, while the Longitudinal Valley Fault is mainly responsible for accommodating thrust motion. [ABSTRACT FROM AUTHOR]

After industrialization, advancements in construction technologies and the rural-to-urban migration that began in the 1950s have led to the transformation of historical city centers. This transformation resulted in the construction of high-rise apartment buildings in proximity, replacing low-rise residential areas. These practices have caused the disappearance of public spaces and increased population density in historical city centers. Over time, the vitality of city centers has diminished, turning them into low-quality, declining areas. Within the scope of building stock, this decay has made these areas more vulnerable and less resistant to disasters. As a result, projects have been prepared for the renewal of these areas, the protection of historical areas and the restoration of the lost vitality in the city centers. Strategies are produced and generally enacted within the scope of sustaining the life span of cities on the slums, increasing welfare, and acquiring building blocks. These places are the Gölcük Earthquake in 1999, the Van Earthquake in 2011 and the earthquake that occurred in the Kahramanmaras in 2023 with serious damage in Hatay, Adıyaman, Gaziantep, and Malatya; demonstrates the importance of overcoming the vulnerability of disaster risk. It is aimed to analyse the built environment and to contribute to the disposal of the evacuations obtained from the analysis, based on the idea that the houses built before 1960 and after 1966 in Amasya, where there is an earthquake in the 1st degree region in this region. The two axes of the order buildings in the working environment, the building floor structure, land use, building quality and construction type analyses and field visuals were made. By evaluating the results obtained within the scope of wear performance, suggestions were made for planning and design practices to minimize the vulnerable in the event of a limited earthquake. [ABSTRACT FROM AUTHOR]

The 2013 Ruisui earthquake represents the first unequivocal evidence of the activity of the Central Range fault (CRF) in central Longitudinal Valley, Taiwan. Using a joint Bayesian finite‐fault source inversion of Global Navigation Satellite System and strain time series, we infer that coseismic rupture occurred between 4 and 19 km depth with maximum slip of 0.5 m located near the hypocenter. We then apply a variational Bayesian independent component analysis approach to displacement signals to infer a 3‐months long afterslip located in the near‐source region. This observation represents the first evidence of aseismic slip on the CRF. Combining geodetic and seismological analysis with simulations based on rate‐and‐state friction mechanics, we analyze the interplay between seismic and aseismic deformation during the earthquake sequence. We observe that afterslip is the dominant postseismic deformation mechanism, with >95% of the moment being released aseismically in the postseismic phase and also likely represents the driving force controlling aftershock productivity. Finally, we infer the presence of a shallow velocity strengthening zone (∼0–4 km depth) associated with spatially heterogeneous slip during the postseismic phase with maximum slip of 0.18 m located above the zone of maximum coseismic deformation. Plain Language Summary: Tectonic faults display a broad range of slip patterns, ranging from fast slip (earthquakes) to episodic or continuous aseismic slip. Aseismic transient slip events are now widely observed in active regions and play an important role in stress redistribution in the Earth's crust. The Central Range fault (CRF) is the second most active fault in the Longitudinal Valley, in eastern Taiwan. During the past 15 years, the fault hosted large to destructive earthquakes, but little is known about the presence and the role of aseismic events on the fault deformation. The 2013 Ruisui earthquake reveals for the first time the presence of transient slip regions on the CRF, capable of sustaining aseismic deformation over months. Besides, slow stress relaxation on the fault plane may have also influenced the behavior of seismicity following the mainshock. Monitoring and characterizing the sources of aseismic slip is fundamental to identify areas with high seismic hazard on the fault and to gain more knowledge about the interactions between seismic and aseismic processes. Key Points: We present the first evidence for the detection of postseismic deformation on the Central Range fault, in the Longitudinal Valley (Taiwan)Afterslip represents the dominant deformation mechanism during the postseismic phase and controlled aftershock productionThe velocity strengthening region may have acted like a barrier, resisting the rupture propagation toward the surface during the earthquake [ABSTRACT FROM AUTHOR]

Due to the lack of recognized creep on dip‐slip faults, the nature of fault creep and its role in the generation of large earthquakes is largely unexplored. The Chihshang fault in Taiwan serves as one of the best examples of a thrust creeping fault in the world, exhibiting a fast creep rate of 2–3 cm/year and the capability of producing magnitude six earthquakes. Land‐based geodetic measurements are less sensitive to fault slip with depth, especially for the deeper portion of the seaward dipping fault. Taking advantage of slip rates inferred from repeating earthquake sequences (RESs) at greater depths (up to 30 km), we present a method that embeds RES‐derived slip rates into the neighboring fault patch for geodetic data inversion. Using the geodetic and seismological data from 2007 to 2011, we achieve a higher resolution of inter‐seismic slip rate distribution below a depth of 10 km. The inferred low coupling ratio establishes an extensive creeping area that coincides with a location of abundant RES and earthquake swarms. The inferred high coupling ratio, on the other hand, delineates a locked area corresponding to the two co‐seismic slip zones of the 2003 Mw 6.8 Chengkung and 2022 Mw 6.7 Yuli earthquakes. The transition zone marking the gradual change from fully locked to shallow creeping areas appears to coincide with the post‐seismic slip area of the 2003 Chengkung event. Using the fault coupling model, the moment rate deficit measured in the two locked areas is capable of generating a Mw 6.8 event every 78 years to the south and a Mw 6.7 event every 28 years to the north. This moment rate deficit is decreased by 10% when the closely located Central Range fault is considered in a two‐fault model, leading to the slightly longer recurrence interval on the Chihshang fault. The two‐fault model potentially contributes to a better understanding of the regional inter‐seismic deformation, which is recommended to be adopted in the future studies of seismic hazard assessment. Plain Language Summary: Large earthquakes can occur on the creeping faults that slowly slip at the surface but accumulate energy at greater depth. How much different portions of the fault slip annually is the key question for seismic hazard assessment. However, for a seaward‐dipping thrust fault like the Chihshang fault in Taiwan, finding the answer is difficult because the loss of resolution at the greater depth (>10 km) due to a lack of offshore data. Taking advantage of the slip rates inferred from repeating earthquakes that mainly occurred at 10–30 km depth, we present a method that embeds repeating events data into the geodetic inversion for higher resolution of inter‐seismic slip model. We found that the areas slipped faster during the inter‐seismic period (higher inter‐seismic slip rate) coincides with the location of abundant repeating earthquakes and swarm events; The areas with lower inter‐seismic slip rate on the other hand, correspond to the zones that slipped during the 2003 Mw 6.8 Chengkung and 2022 Mw 6.7 Yuli earthquakes. By calculating how much and where the seismic energy was released through inter‐seismic slip rate, we are able to identify two separate zones on the Chihshang fault that is capable of generating a ∼Mw 6 event every 28 to the north and 78 years to the south of the fault, respectively. Key Points: We present a method that embeds repeaters‐derived slip rates into the neighboring fault patch for geodetic data inversionWe achieve a higher resolution of inter‐seismic slip rate distribution below a depth of 10 km, on a seaward‐dipping thrust faultThe inferred low coupling ratio establishes an extensive creeping area, coinciding with the location of active repeaters and swarm events [ABSTRACT FROM AUTHOR]

The problem of estimating earthquake risk is one of the primary themes for researchers and investigators in the field of geosciences. The combined assessment of spatial probability and the determination of earthquake risk at large scales is challenging. To the best of the authors' knowledge, there no updated earthquake-hazard-and-risk assessments for the Eurasia region have been published since 1999. Considering that Eurasia is characterized by a seismically active Alpine–Himalayan fault zone and the Pacific Ring of Fire, which are frequently affected by devastating events, a continental-scale risk assessment for Eurasia is necessary to check the global applicability of developed methods and to update the earthquake-hazard, -vulnerability, and -risk maps. The current study proposes an integrated deep-transfer-learning approach called the gated recurrent unit–simple recurrent unit (GRU–SRU) to estimate earthquake risk in Eurasia. In this regard, the GRU model estimates the spatial probability, while the SRU model evaluates the vulnerability. To this end, spatial probability assessment (SPA), and earthquake-vulnerability assessment (EVA) results were integrated to generate risk A, while the earthquake-hazard assessment (EHA) and EVA were considered to generate risk B. This research concludes that in the case of earthquake-risk assessment (ERA), the results obtained for Risk B were better than those for risk A. Using this approach, we also evaluated the stability of the factors and interpreted the interaction values to form a spatial prediction. The accuracy of our proposed integrated approach was examined by means of a comparison between the obtained deep learning (DL)-based results and the maps generated by the Global Earthquake Model (GEM). The accuracy of the SPA was 93.17%, while that of the EVA was 89.33%. [ABSTRACT FROM AUTHOR]

On 17–18 September 2022, an earthquake sequence with a moment magnitude of 6.6 foreshock and a 7.0 mainshock occurred in southeast Taiwan along the Longitudinal Valley. Several surface breaks and collapsed buildings were observed after the event and one person died. The focal mechanisms of the foreshock and mainshock both had a west-dipping fault plane, which is different from the known active east-dipping boundary fault between the Eurasian Plate and the Philippine Sea Plate. Joint source inversions were performed to better understand the rupture mechanism of this earthquake sequence. The results show that the ruptures mainly occurred on a west-dipping fault. In the mainshock, the slip originated from the hypocenter and propagated toward the north with a rupture velocity of approximately 2.5 km/s. The east-dipping Longitudinal Valley Fault also ruptured, which could be passive and dynamically triggered by the significant rupture on the west-dipping fault. Most importantly, this source rupture model together with the occurrence of large local earthquakes over the past decade strongly supports the existence of the Central Range Fault, which is a west-dipping boundary fault that lies along the north to south ends of the Longitudinal Valley suture. [ABSTRACT FROM AUTHOR]

The Salton Sea Geothermal Field (SSGF) is one of the most seismically active and geothermally productive fields in California. Here we present a detailed analysis of short-term seismicity change in SSGF from 2008 to 2013 during and right following large distant earthquakes, as well as long-term seismicity change due to geothermal productions. We first apply a GPU-based waveform matched-filter technique (WMFT) to the continuous data recorded by the Calenergy Borehole (EN) Network and detect more than 70   000 new micro-earthquakes than listed in the standard Southern California Seismic Network catalogue. We then analyse the seismicity rate changes in the SSGF associated with transient stress fluctuations triggered by regional and large teleseismic earthquakes from 1999 to 2019. We find triggered seismicity in the SSGF following seven regional M  > 5.5 earthquakes. In comparison, most teleseismic earthquakes with M  > 8.0 did not trigger significant seismicity rate change in the SSGF, likely indicating a frequency dependence in remote dynamic triggering. We further characterize the correlation between the long-term seismicity rate and geothermal production rates, and the temporal and spatial distribution of Guttenberg–Richter b -values inside and outside the SSGF with the newly detected catalogue. The long-term seismicity shows that events with M > 1.5 are likely correlated with net production rates, while smaller events do not show any correlation. The b -values inside the SSGF are higher than those outside the SSGF, and the locations of dynamically triggered events are close to locations with high b -values. [ABSTRACT FROM AUTHOR]

After the 1999 Marmara earthquake, serious damages occurred in some of the drinking water networks of Sakarya province, and almost all of the sewerage networks became inoperable. In this study, the vulnerability of buried pipes, which constitute a large part of the potable water supply and distribution networks of the infrastructure systems of Sakarya province, against seismic hazards were analyzed by the Hazard US (HAZUS) method. The maximum ground velocity used in the analysis of the vulnerability of buried pipes against possible earthquakes was determined with the help of classical probabilistic earthquake hazard analysis. Soil classes used in vulnerability analysis were calculated with the help of seismic data taken from 2044 points throughout the province. Sakarya province potable water pipe inventory was created and vulnerability parameters were defined for all pipes with the help of geographic information systems. The HAZUS method, which is frequently used in the literature, was used for pipe vulnerability analysis. As a result of the analysis, damage repair rates expressing the vulnerability of all pipes were obtained and the pipes were classified according to their damage repair rates. [ABSTRACT FROM AUTHOR]

The 17 August 1999 Mw7.4 Izmit earthquake ruptured the western section of the North Anatolian Fault Zone and strongly altered the fault zone properties and stress field. Consequences of the co‐ and post‐seismic stress changes were seen in the spatio‐temporal evolution of the seismicity and in the surface slip rates. Thirteen years after the Izmit earthquake, in 2012, the seismic network Dense Array for North Anatolia (DANA) was deployed for 1.5 years. We built a new catalog of microseismicity (M < 2) by applying our automated detection and location method to the DANA data set. Our method combines a systematic backprojection of the seismic wavefield and template matching. We analyzed the statistical properties of the catalog by computing the Gutenberg‐Richter b‐value and by quantifying the amount of temporal clustering in groups of nearby earthquakes. We found that the microseismicity mainly occurs off the main fault and that the most active regions are the Lake Sapanca step‐over and near the Akyazi fault. Based on previous studies, we interpreted the b‐values and temporal clustering (a) as indicating that the Akyazi seismicity is occurring in high background stresses and is driven by the Izmit earthquake residual stresses, and (b) as suggesting evidence that an intricate combination of seismic and aseismic slip was taking place on heterogeneous faults at the eastern Lake Sapanca, near the brittle‐ductile transition. Combined with geodetic evidence for enhanced north‐south extension around Lake Sapanca following the Izmit earthquake, the seismicity supports the possibility of slow slip at depth in the step‐over. Plain Language Summary: On 17 August 1999, a large M7.4 earthquake struck near the city of Izmit, in western Turkey, and caused important human and material losses. The earthquake resulted from the large and sudden displacement of crustal blocks along the North Anatolian Fault Zone (NAFZ). Transient changes in the crustal and fault properties are commonly observed following such large events. In this study, we analyze the statistical properties of microearthquakes, that is, of small earthquakes (M < 2) typically too small to affect the surrounding population, to gain knowledge about the state of the NAFZ more than a decade after the Izmit earthquake. First, we address the challenge of locating microearthquakes, in space and time, by applying our automatic earthquake detection and location algorithm. Then, we use a statistical analysis to characterize physical properties of the NAFZ and, thus, to highlight the peculiar properties of faults near Lake Sapanca. We interpret that these faults are heterogeneous and slip both seismically and aseismically. Our study calls for taking a closer look at the extension across Lake Sapanca with different, complementary geophysical methods. Key Points: We build an extensive earthquake catalog using our new fully automated method along the western North Anatolian Fault Zone (NAFZ)We observe variable statistical properties (b‐value and temporal clustering) along the NAFZHigh b‐value and strong temporal clustering may suggest the occurrence of slow slip in the Lake Sapanca step‐over [ABSTRACT FROM AUTHOR]

Earthquake waveforms are necessary for simulation, verification, and validation during the development of structural and earthquake engineering. However, due to the fact that the processes of earthquake preparation and generation are extremely complex and the human observations cover a relatively short period compared to large earthquake cycles, recorded earthquake waveforms are often limited and quite imbalanced. Consequently, the generation of artificial earthquake waveforms is meaningful and can produce useful earthquake data. In this study, a new method based on a generative approach is proposed by leveraging machine learning (ML) techniques. The generative models based on generative adversarial network (GAN) and conditional GAN (cGAN) are introduced, and the adversarial training between the generator and the discriminator is utilized to learn how to generate artificial earthquake waveforms. In addition, several criteria are exploited to terminate the adversarial training early in order to prevent modal collapse. Besides, different earthquake datasets and several earthquake features are used to verify the proposed method. The preliminary generation is carried out using the dataset recorded during the Chi-chi earthquake, and the generated samples show similar earthquake features to those extracted from the earthquake dataset. Subsequently, conditional generation is conducted using several sub-datasets recorded in different areas around Taiwan. The results demonstrate that the well-trained model can efficiently generate waveforms according to a pre-specified seismic intensity, with an overall accuracy of up to 90%. Although the model is reliable for Taiwan and in general to restricted subdomain of the probability distribution support, the proposed method shows its ability to produce new samples for a given class, even when the number of generated samples exceeds the number of training samples. • A large number of artificial earthquake waveforms are generated by using generative adversarial networks (GAN). • Several criteria based on the generated samples are used to terminate the adversarial training early to avoid modal collapse. • The conditional generation enables GANs to generate artificial earthquake waveforms according to various labels. [ABSTRACT FROM AUTHOR]

Ground motion amplification has been observed in most earthquakes triggered near the sediment-filled basins such as 2015 Nepal and 1999 Chi–Chi events. Many numerical studies pointed out the effect of various parameters such as material properties and geometric features of the basin on ground motion amplification but the effect of the complete range of source mechanism parameters needs to be addressed. This paper presents the effect of source mechanism parameters, such as strike, dip, rake angle of fault and moment magnitude ( M w) on amplification of ground motion intensity measures (IMs) due to sediment-filled basins. It is found out that the maximum spectral amplification, when subjected to the source of lateral strike mechanism, is 45, whereas for thrust fault mechanism, it is 30. Within the lateral strike mechanism, if the dip angle is increased from 0∘ to 90∘, the spectral amplification increases from 10 to 30 times. The results also suggested that it is important to consider detailed focal parameters to study basin amplification. The amplification of IMs in the basin is more sensitive to variation of dip angle than the other source parameters and the magnitude of earthquake has an insignificant role in basin amplification. [ABSTRACT FROM AUTHOR]

The southern Ryukyu subduction zone is one of the potential sources for tsunamigenic earthquakes. Despite a great seismic risk, the deformation pattern remains poorly known, primarily due to the absence of seafloor constraints. With GNSS‐acoustic measurements over years, we characterize the convergence rate across this margin growing from 92 mm/yr offshore eastern Taiwan to 123 mm/yr near the Gagua Ridge. The new data suggest the subduction interface is capable of hosting Mw 7.5–8.4 earthquakes. The orientations of seafloor movement and P‐axes in the Nanao Basin are both subnormal to the trench, notably deviate from the direction of plate convergence. By considering the combined effect of plate convergence and backarc rifting, different trends between the forearc convergence, P‐axes, and seafloor movement may indicate some degree of slip‐partitioning. The trench‐parallel component is likely accommodated in part by earthquakes near Taiwan, lower plate deformation, and strike‐slip faults within the accretionary wedge. Plain Language Summary: The southern Ryukyu margin near Taiwan accommodates the relative plate motion and backarc rifting. This region has suffered from tsunamis and large earthquakes with magnitudes of about eight in the history, yet insufficient offshore data still hamper our ability to fully characterize fault slip behaviors. We demonstrate how a seafloor geodetic technique, with the combination of the Global Navigation Satellite System and acoustic ranging, can help us constraining fault slip behaviors and assessing seismic risks. We infer a fraction of oblique plate motion is accommodated by the subduction interface capable of hosting earthquakes with moment magnitudes ranging from 7.5 to 8.4. Incorporating seismological observations, we find different trends of the compressive axes of earthquakes, seafloor movement, and the forearc convergence, which may indicate some degree of strain partitioning. The trench‐parallel motion is partially taken up by seismic slip near Taiwan, subducting plate deformation, and strike‐slip faults within the forearc. More near‐trench observations are crucial to assessing seismic hazard and evaluating strain partitioning along the southern Ryukyu Trench. Key Points: Rapid convergence across the southern Ryukyu margin increases eastward from 92 mm/yr offshore Taiwan to 123 mm/yr near the Gagua RidgeOblique convergence is accommodated in part by the plate interface fault capable of hosting earthquakes with Mw 7.5–8.4Different trends between the forearc convergence, P‐axes, and seafloor movement may indicate some degree of slip partitioning [ABSTRACT FROM AUTHOR]

Understanding the stress state before and after an earthquake is essential to study how stress on faults evolves during the seismic cycle. This study integrates wellbore failure analysis, laboratory experiments, and edge dislocation model to study the stress state before and after the Chi‐Chi earthquake. The post‐earthquake in‐situ stress state observed along boreholes of the Taiwan Chelungpu‐fault Drilling Project (TCDP) is heterogeneous due to lithological variations. Along the borehole, we observe that drilling‐induced tensile fractures are only present in sandstones, whereas breakouts are mostly present in silt‐rich rocks. Laboratory experiments on TCDP cores also show that tensile and compressive strength are weaker in sandstones than in silt‐rich rocks. These observations imply that both maximum and minimum horizontal principal stresses are higher in silt‐rich intervals. Extended leak‐off tests in the TCDP borehole also show lower minimum horizontal stress in sand‐rich intervals, consistent with the above observations. We combine these observations to estimate a profile of stress magnitudes along the well which explains the variability of stress states found in previous studies. The stress heterogeneity we observed underlines the importance of acknowledging the spatial scale that the stress data represent. We then use an edge dislocation model constrained by GPS surface displacements obtained during Chi‐Chi earthquake to calculate the coseismic stress changes. Our inferred pre‐earthquake stress magnitudes, obtained by subtracting the coseismic stress change from the post‐earthquake stress, suggest subcritical stress state before the earthquake despite the large displacements observed during the Chi‐Chi earthquake in the region where TCDP encountered the fault. Plain Language Summary: Stress in the Earth's crust defines the forces acting on faults which drive earthquakes. Therefore, tracking how stress accumulates due to plate motion and is released due to fault slip have been a central topic in the study of earthquake mechanics and associated seismic hazard. Previous studies which analyzed data collected from Taiwan Chelungpu‐fault Drilling Project (TCDP), drilled after the 1999 Chi‐Chi earthquake, show that the post‐earthquake stress inferred from those studies is inconsistent with each other. This study reviewed previous measurements, conducted laboratory experiments, and analyzed borehole data to revisit the stress state after the Chi‐Chi earthquake. We show that stress state varies along the TCDP borehole due to lithology and fault‐related changes in mechanical properties, which explains why past studies indicated significant variability. We also estimated the pre‐earthquake stress before the Chi‐Chi earthquake to understand stress conditions leading to the rupture. We calculated the stress change caused by the Chi‐Chi earthquake and subtract it from the post‐earthquake stress to obtain the pre‐earthquake stress. Our pre‐earthquake stress estimate suggests that the stress before the Chi‐Chi earthquake was low in magnitude compared to the frictional strength of rocks. Key Points: We obtain a near‐continuous stress profile which captures the lithology‐dependent and fault‐related stress variation along the boreholesVariability in stress states reported from previous studies is explained by stress variations caused by lithological variationsThe estimated pre‐earthquake stress profile indicates subcritical stress state within the Chelungpu fault zone prior to the earthquake [ABSTRACT FROM AUTHOR]

Earthquakes play a fundamental role in the evolution of Earth's topography through co-seismic uplift and subsidence, as well as erosion through widespread landslides induced by ground motion. Earthquake-induced landslides can result in exceptional increases in the transfer of mass from landscapes, supplying sediment to rivers where impacts can last for decades or longer. Landslides can also erode vegetation and soils, in addition to exposing freshly ground rock mass, which can both result in regionally significant carbon transfers. Recent work has sought to quantify the fluxes, rates, and temporal patterns of the impacts on earth surface processes generated by these tectonic events. In this review, we focus on the impacts of earthquake-induced landslides on erosion and sediment flux, river water chemistry, and carbon export through the lens of the well-studied 2008 Wenchuan earthquake. We then discuss these themes in the context of works from the 1999 Taiwan Chi-Chi earthquake, 2015 Nepalese Gorkha earthquake, and New Zealand historical earthquakes, altogether highlighting an important role of earthquake-induced landslides in erosion and weathering along tectonically active mountain ranges. We suggest that more monitoring, geochemical tracing, paleo-records, and/or modelling studies are needed to compare the processes and fluxes of catchment erosion and weathering before and after earthquake events, which will help to deepen our understanding not only of the impacts of earthquake-induced landslides on earth surface processes, but also the linkage among high magnitude events, continental erosion and weathering, and the long-term global carbon cycle. [ABSTRACT FROM AUTHOR]

The earthquake early warning (EEW) system in Taiwan is the outcome of rigorous research work carried out at various levels after the occurrence of the 1986 Hualien earthquake that caused destruction. After more than 25 years of development, three different EEW systems exist in Taiwan. Currently, the nation wide regional EEW system is operated by the Central Weather Bureau (CWB), whereas, a hybrid (regional & onsite) system based on Micro-Electro-Mechanical System sensors is run by National Taiwan University (NTU). The third EEW (onsite system) is run by the National Center for Research on Earthquake Engineering (NCREE). Both CWB and NTU systems are capable of reporting the EEW warnings within 20 seconds of earthquake occurrence. The CWB system is incharge of providing earthquake alerts in Taiwan via text message through mobile phone, TV, and directly broadcasting system to schools and is providing earthquake alarms to the general public since 2016. During recently damaging earthquakes in Taiwan, the NTU system provided 2–8 seconds onsite warning (lead time) in the blind zone around the epicenter. The NTU system also can generate near real-time shake maps for rapid response purposes. The NCREE system consists of about 98 stations and can provide several seconds lead time in the area near the epicenter. The NCREE system also can receive CWB regional EEW messages for warning the regions away from the epicenter. Individually every system has its advantage, however, the hybrid approach will be one of the future systems for real operation. [ABSTRACT FROM AUTHOR]

The Taiwan–Ryukyu arc–trench junction area is a seismic active region and has high potential to generate large earthquakes. However, the detailed deep structures are not fully revealed because of data resolution problems. The Taiwan Integrated Geodynamic Research (TAIGER) project collected two wide‐angle and multichannel seismic profiles across the Taiwan mountain belt (T5) and the western end of the Ryukyu arc–trench system (T6). In this study, we perform 2‐D gravity modelling for T5 and T6 by taking advantage of well‐constrained P‐wave velocity models, which helps to reduce the nonunique problem. To better fit the observed gravity anomaly, a block with relatively high‐density must exist beneath eastern Taiwan. This high‐density material could be serpentinised mantle, which may be resulted from the dehydration of the subducting Eurasian plate. Also, our result indicates that the subducting Gagua Ridge has a deep crustal root and extends northward to the Ryukyu forearc area. [ABSTRACT FROM AUTHOR]

The precursor time, T, is the time interval between the occurrence time of a precursor and that of a forthcoming earthquake with local magnitude, ML. The precursors are classified into four types of earthquake prediction with different time windows: long-term prediction (T = 3 to 10 years); intermediate-term prediction (T = 6 months to 3 years); short-term prediction (T = 8 days to 6 months); and imminent prediction (T = 7 days). Since the 1999 Chi-Chi earthquake, the precursors for numerous earthquakes in Taiwan have been observed and studied. The values of T and ML are compiled from scientific literature. The plots of T versus ML are made for some precursors when the data sets are large with the values of T for respective events. Such precursors are the b-value anomalies, foreshocks, thermal infrared radiation anomalies, geochemical composition changes, radon changes, γ-ray emission anomalies, and total electron content (TEC) anomalies. There is a positive correlation between T versus ML for the b-value anomalies, foreshocks, Rn changes, and γ-ray emissions. The relationship of log(T) versus ML is also inferred for Rn changes. The precursor time for Rn changes is positively correlated with that for γ-ray emissions. The time difference between the precursor time for Rn changes and that for γ-ray emissions is positively correlated to ML. However, the plots for thermal infrared radiation, geochemical composition changes, and TEC anomalies are quite scattered and thus not any correlation can be obtained. The positive correlations between T and ML or some precursors suggest the possibility of earthquake prediction in future. [ABSTRACT FROM AUTHOR]

Historical masonry arch bridges which might be vulnerable to natural disasters are important part of the cultural heritage. Natural disasters, especially earthquakes can inflict damage to these structural systems. This paper aims to investigate a comparison of the effects of near and far-fault ground motions on the seismic response of masonry arch bridges under different earthquakes. Kalender masonry arch bridge which is located in Ergani, Turkey is selected as a numerical model. For this purpose, three-dimensional finite element model of the bridge is generated with ANSYS finite element software with macro modelling approach. Seismic response of the bridge is assessed by means of time-history analyses. The near-fault and far-fault ground motions, which have approximately equal peak ground accelerations, of 1979 Imperial Valley, 1999 Chi-Chi, 1999 Kocaeli and 2010 Darfield earthquakes are considered for the analyses. Comparisons between maximum displacements, maximum and minimum stress, which were acquired from the dynamic analyses of the masonry bridge subjected to each fault effect, are obtained. The study demonstrates that far-fault ground motions are as important as near-fault ground motions and it can be used together with near-fault ground motion for further evaluation of such historical masonry bridges. [ABSTRACT FROM AUTHOR]

Earthquake prediction has been a long-term debatable problem in earthquake science. There were numerous studies of possible precursors after the Mw 7.6 Chi-Chi, Taiwan, earthquake of 20 September 1999. A deep study about these precursors will be useful for the exploration of the debatable problem. In this study, based on the time window (or the precursor time, T) prediction for earthquakes in Taiwan are defined as follows: very-long-term prediction (T > ten years or longer); long-term prediction (ten years> T > three years); intermediate-term prediction (T = six months to three years); short-term prediction (T = eight days to six months); and imminent prediction (T = seven days). Meanwhile, the precursors are classified into four categories: mechanical, electromagnetic, geochemical, and biological precursors. Each category may include several items. First, we will compile all given possible precursors and the respective precursor times. Secondly, we will examine these possible precursors based on known physical and chemical theories. Thirdly, we will discuss the possible correlations between two precursors. From the results of this study, most of precursors are reliable and few of them need re-examinations. This suggests the possibility of earthquake prediction. Nevertheless, earthquake scientists cannot yet preciously predict an earthquake just based on the reliable observations. Like weather forecasting, it is very necessary to construct the physical and chemical models of respective precursors or even a unified model for all precursors. Based on the models or a unified model, it is possible to predict earthquakes. [ABSTRACT FROM AUTHOR]

The 1604 Quanzhou earthquake occurred offshore southeastern China in the Taiwan Strait and with magnitude estimated ranging from 7.5 to 8.0, which is the largest earthquake observed in the low seismicity zone of the Taiwan strait for the last 400 years. According to literature, this earthquake caused several casualties and severe damage along the coast of southeastern China. Although no document reported the impact of this earthquake on Taiwan, the impact of an earthquake like the 1604 Quanzhou event is of great concern for the region considering the densely populated areas on both sides of the Taiwan Strait. In this study, we review the literature and past studies of this earthquake, and we simulate the level of ground shaking through various models based on past studies. Our results show that the 1604 Quanzhou earthquake had a magnitude of Mw 8.1 with maximum slip of 16 - 20 m on an asperity, and with an average stress drop of 10 MPa. The comparison of the simulation to the developed response spectra suggests that this earthquake brought a larger long period motion (< 0.4 Hz) to Taiwan compared to that from the regional recorded crustal earthquakes. The long period motion from an earthquake in this magnitude scale warrants attention regarding seismic hazard mitigation for high-rise buildings for cities across the Taiwan Strait. [ABSTRACT FROM AUTHOR]

The recent advances in satellite based ionosphere monitoring provided more evidence about earthquake (EQ) precursors from lithosphere ionosphere coupling mechanism. In this paper, we investigate ionospheric anomalies associated with the December 19, 2009, Taiwan EQ (Mw = 6.4), that occurred on UT = 13:02 h. Seismo ionospheric anomalies are evaluated during 31 days (20 day before followed by 10 days after the EQ) in the data of French Satellite Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) and validated from Global Navigation Satellite System (GNSS) retrieved Total Electron Content (TEC). The day time values of ISL (Langmuir Probe) and IAP (Ion Analyzer) from DEMETER point to significant ionospheric perturbations within 5 days associated with EQ day. Moreover, GNSS stations of International GNSS Service (IGS) within EQ preparation zone also validate anomalies in ionosphere prior/after the Mw 6.4, Taiwan EQ. Moreover, spatial and temporal analyses of daily ionospheric indices from DEMETER and GNSS point to simultaneous enhancement in electron density, ion density, electron temperature and TEC related to the main shock during quiet geomagnetic storm (Dst < − 30 nT, Kp ≤ 3). All these evidence aids in promoting the lithosphere- ionosphere coupling over the epicenter of Mw 6.4 during the preparation period from DEMETER and GNSS TEC. [ABSTRACT FROM AUTHOR]

Due to the global climate change and the substantial increase in impervious area, 'never flooding' becomes an unrealistic goal. From the perspective of integrated flood management, the government and public need to reach a consensus on disasters and disaster response, and set a reasonable regional protection standard for the city to jointly respond to disasters. This study establishes an operable framework for setting protection standard. The framework uses cost-benefit analysis and data envelopment analysis to maximize the efficiency of water management, so as to compare the differences between different administrative districts under the same return period and between different return period under the same administrative districts, and then determines the best protection standard. The results find that adopting a unified protection standard will not maximize the benefits of resources, but it can be used as a basis for setting flood control standards for different public facilities and building types. [ABSTRACT FROM AUTHOR]

Recently, researchers have conducted long-term statistical studies to prove the correspondence between earthquakes and thermal infrared (TIR) anomalies. Upon obtaining relatively high true positive rates (TPR), it was concluded that TIR anomalies are closely related to earthquakes. However, the temporal-spatial clustering of earthquakes and overly large temporal-spatial windows will also contribute to high TPRs, and it is improper to correlate TIR anomalies with earthquakes without excluding these influences. In this paper, relevant studies will be tested according to the prior probability, random earthquake catalogs and Molchan diagram weighted by the Relative Intensity (RI) index. Our results show that the high TPR in the previous studies were caused by overly large determining windows, and the result was close to random guessing, which means that the extracted TIR anomalies make no contributions to predicting the timing, epicenter and magnitude of earthquakes. By comparing the original Molchan diagram and the Molchan diagram weighted by the RI index, we found that simply taking the fraction of space-time occupied by alarm may give a wrong evaluation for alarm. Moreover, long-term statistical evidence proving the correspondence between earthquakes and TIR anomalies in Greece and Taiwan are still absent. [ABSTRACT FROM AUTHOR]

We present a magnetic fabric investigation of small oriented rock fragments from gouges and wall rocks from the Chelungpu fault (Taiwan), where the Chi‐Chi earthquake occurred (Mw 7.6, 1999). Samples are obtained from surface outcrops and at a depth of ~1 km, including the 3‐mm‐thick Chi‐Chi principal slip zone. Wall rocks at depth show magnetic foliation roughly parallel to bedding, whereas they are oblique at the surface. Within the gouges, the mean shape of magnetic ellipsoid is oblate, and the degree of anisotropy is up to 12%. The magnetic foliation diverges of ~40° from the fault plane, compatible with a simple shear westward. The magnetic lineation is oblique, resulting probably from coseismic and interseismic records. The reconstructed focal mechanism from the magnetic fabric closely matches the focal mechanism solutions for the Chi‐Chi earthquake. Our work demonstrates that magnetic fabric of gouge fragments can bring valuable kinematic information on modern earthquakes. Plain Language Summary: Fault gouges often provide important and valuable information that can help to understand the fault mechanisms and to assess the seismic hazard, but to get access to the shape preferred orientation of micrometric minerals is generally a complex, time consuming and expensive procedure. In this study, we show that the anisotropy of magnetic susceptibility, which is a fast and nondestructive technique, can be a proxy of the structural fabric of historical gouges. This technique has already been previously applied to gouge zones, but this is the first time that it is used in the gouge from one of the best documented historical large seismic events: the 1999 Chi‐Chi earthquake (Mw 7.6) along the Chelungpu fault (Taiwan). Samples within and around this fault were obtained from fresh surface outcrop and 1‐km‐deep borehole (Hole B, Taiwan Chelungpu‐fault Drilling Project). The 1‐km‐deep gouge hosts the 3‐mm‐thick principal slip zone of the Chi‐Chi earthquake. The results show that the reconstructed focal mechanism based on the magnetic fabric geometry matches closely the focal mechanism solutions for the Chi‐Chi earthquake estimated by several previous studies. Key Points: For the first time, the bulk fabric of small fragments of historical gouge, including the 1999 Chi‐Chi earthquake (Mw 7.6) slip zone, has been analyzed successfullyThe bulk fabric of gouge is anisotropic, reflecting the grain orientation of billions of clays and magnetic particlesThe magnetic fabric of gouge mimics the focal mechanism solutions of historical earthquakeWe provide a new tool to elucidate earthquake properties from fault gouges [ABSTRACT FROM AUTHOR]

Observations from several earthquakes indicate that near-fault (NF) ground motions have a significant influence on the seismic response of structures. However, existing studies have only discussed the influence of a certain NF characteristic on the seismic response, rather than systematically discussing and comparing the influence of different NF characteristics. Furthermore, current research is only suitable for a specific structure while the influence of NF characteristics on structures with different dynamic characteristics has not been revealed. As an important lifeline project, the safety of a cable-stayed bridge (CSB) during earthquakes is of great concern. Therefore, this paper investigates the influence of NF ground motions on the seismic response of CSB. Firstly, three major characteristics (i.e., the hanging wall effect, rupture directivity effect and high velocity pulse) of NF ground motions are analyzed using NF records of the Chi–Chi earthquake. Secondly, a finite element (FEM) model for modeling a prototype CSB is developed and benchmarked. Then, the seismic responses of the prototype CSB subjected to NF ground motions with different characteristics are analyzed using the benchmarked FEM model. The analyses show that hanging wall effect, rupture directivity effect, and high velocity pulse affect the seismic demand of the CSB to varying degrees. Furthermore, the influences of NF characteristics on the displacement response of CSBs with different fundamental periods are investigated using SDOF systems. The analysis results show that different NF characteristics have various influences on the displacement response of CSBs with different fundamental periods. [ABSTRACT FROM AUTHOR]

This paper shows that while China now attaches geostrategic importance to Taiwan, it has not always done so. It has only accorded such significance to Taiwan in the post-Mao era. By reviewing how Taiwan became a Japanese colony, how it came under the control of Chiang Kai-shek's government, and how it came to be seen by the government of the People's Republic of China as a sacred territory before being deemed geostrategically significant, this paper seeks to demonstrate that Taiwan's importance to China is not based on geography, an immutable factor. Instead, it was the result of contingencies of history and the changed calculations of succeeding governments in China. This leads to the important conclusion that the geostrategic importance the Chinese government now attaches to Taiwan may change if the Chinese leadership alters its strategic calculus or if the government itself is replaced. [ABSTRACT FROM AUTHOR]

Satellite measurements are becoming popular among the scientific community to identify earthquake precursors since its spatial coverage is more and round the clock measurements are possible. In this paper, we analyzed Total Electron Content (TEC), Outgoing Longwave Radiation (OLR), Sea Level Pressure (SLP), Surface Latent Heat flux (SLHF) and Sea Surface Temperature(SST) to identify any abnormal anomalies before Taiwan earthquakes which occurred on 4th February 2018 (M = 6.1, depth = 12 km) and 6th February 2018 (M = 6.4, depth = 17 km). The GPS data of International GNSS Service(IGS) stations (TWTF and CKSV) which operated 90 and 200 km away from the epicenter of the earthquake on 6th February 2018 respectively, were used for calculation of VTEC. The locations of these stations are within the preparatory zone of these earthquakes. The global parameters such as Dst, Kp, and IMF are also analyzed for the corresponding period of VTEC. We noticed the raise of temporal variations of 5–8 TECU before few days of the present earthquakes. The VTEC and other parameters such as SLP, SST, SLHF, and OLR were analyzed using the "Sliding Interquartile range method" during the period of 09th Jan to 10th Feb 2018 (33 days) to identify the abnormal signal due to these earthquakes. Strong positive anomalies occurred one day before the earthquake of 4th February and 1st, 3rd and 5th day before the Taiwan earthquake of 6th February 2018 with strong anomalous nature with an absolute amplitude of 5–8 TECU.The Cross wavelet analysis between Kp and TEC is carried out to study the impact of global geomagnetic activity on TEC during the seismic event and we found a negligible influence of global geomagnetic activity. The good raise of SLP on the day of the earthquake on 6th February 2018 have been noticed with the raise of 300 mb, the SLHF anomalies are observed at the interface of the earth's surface and atmosphere. Moreover, anomalous variations in air temperature and OLR were observed 2 days before the occurrence of the earthquake on 6th February 2018. Well co-ordinated scrutiny of various parameters such as TEC, SLHF, and OLR indicates that they can be used as promising precursors to the impending devastating earthquakes with reasonable accuracy. [ABSTRACT FROM AUTHOR]

Large dip‐slip earthquakes have a major contribution to mountain building while earthquake‐induced landslides lower mountains simultaneously. The amount of the coseismic uplift and landslides may dominate long‐term mountain evolution. However, how earthquakes contribute to mountain evolution through coseismic uplift and landslides is less constrained in real cases. We present the regional coseismic uplift of the 1999 Mw7.6 Chi‐Chi earthquake by using synthetic aperture radar (SAR) images and GPS. The coseismic uplift pattern is consistent with field observations showing increasing movement to the north with ~8 m of uplift toward the northern end. We estimated uplifted rock volume of 2.60 ± 1.09 km3, which is five times greater than the coseismic landslide volume. Intense erosion of the Taiwan orogen may erode elevated rocks rapidly, but the uplift and landslide distributions do not match and correlate more inversely, suggesting the frontal orogenic topography should be increased rather than annulled over earthquake cycles. Plain Language Summary: Earthquakes can raise mountains but they can cause landslides to lower the mountains at the same time. For large earthquakes, mountains could reduce the size due to more landslides than uplift. It is important to analyze earthquakes occurred within mountain ranges to examine how much volume of rocks is elevated and how much volume of rocks is trampled down. Because complete observations of uplift and landslides for large earthquakes are rare, we used geodetic methods to estimate the volume of the elevated rocks for one of the largest earthquakes in mountain ranges in the world, the Chi‐Chi, Taiwan, earthquake in 1999. The volume of elevated rocks is much larger than the landslide volume, and the uplift area is close to the frontal mountains and the landslide areas are distributed in the deeper mountains. If this finding holds for other mountain ranges in similar settings, this means that large earthquakes should raise mountains, especially in the frontal part of the mountains. Key Points: We estimate the regional pattern of the coseismic uplift of the Chi‐Chi earthquakeIncreased rock volume is significantly greater than coseismic landslide volume for the Chi‐Chi earthquakeThe distributions of coseismic uplift and landslides suggest differential topographic increase at frontal orogen [ABSTRACT FROM AUTHOR]

Taiwan that is located at the junction of the Eurasian Plate and the Philippine Sea Plate is one of the most active seismic zones in the world. Devastating earthquakes have occurred around the island and have caused severe damages from time to time. To avoid the severe loss, earthquake early warning (EEW) is of great importance, and one of the most critical issues of EEW is fast and reliable detection for the presence of earthquakes. Traditional methods for earthquake detection usually use criterion-based algorithms to detect the onset of the earthquake waves. Currently, the thresholds for those criteria are usually decided empirically and may result in excessive false alarms. Obviously, false alarms can cause undue panics and diminish the credibility of the system. In this article, the recurrent neural network (RNN) models are adopted to develop a real-time EEW system. The developed system is designed to identify the occurrence of an earthquake event, and the duration of the P-wave and the S-wave. It was trained and tested using the seismograms recorded in Taiwan from 2016 to 2017. From the simulation results, the proposed scheme outperforms the traditional criterion-based schemes in terms of detection accuracy and processing time. [ABSTRACT FROM AUTHOR]

South Korea and Taiwan are former Japanese colonies that have undergone similar processes of state-building since WWII. But they have chosen different rhetorical frameworks in their maritime disputes with Japan. In South Korea, negotiating with Japan can be viewed as threatening the country's independence and pride, whereas in the Taiwanese government, cooperation with Japan is considered mutually beneficial. Why have these two countries taken such divergent stances toward Japan? This article examines the territorial disputes between South Korea and Japan over Dokdo, and between Taiwan and Japan over the Senkaku Islands. It sets forth a rhetorical framework of comparison, and it proposes a constructivist perspective in understanding South Korea's and Taiwan's legitimation strategies toward Japan from the late 1990s to 2018. This comparative study suggests that the differences between their legitimation strategies can be traced to their different colonial experiences with Japan. [ABSTRACT FROM AUTHOR]

• A framework to model UAV-based humanitarian logistics missions is defined. • A mixed integer programming formulation for the problem is presented. • An effective Large Neighbourhood Search approach is proposed to solve this problem. • The algorithm optimises trajectories, depot location and battery allocation. Unmanned Aerial Vehicles (UAVs) are being increasingly deployed in humanitarian response operations. Beyond regulations, vehicle range and integration with the humanitarian supply chain inhibit their deployment. To address these issues, we present a novel bi-stage operational planning approach that consists of a trajectory optimisation algorithm (that considers multiple flight stages), and a hub selection-routing algorithm that incorporates a new battery management heuristic. We apply the algorithm to a hypothetical response mission in Taiwan after the Chi-Chi earthquake of 1999 considering mission duration and distribution fairness. Our analysis indicates that UAV fleets can be used to provide rapid relief to populations of 20,000 individuals in under 24 h. Additionally, the proposed methodology achieves significant reductions in mission duration and battery stock requirements with respect to conservative energy estimations and other heuristics. [ABSTRACT FROM AUTHOR]

This study presents a rapid screening method for health monitoring of building structures based on earthquake records. Compared with conventional damage detection techniques, the rapid screening system with few sensors is more attractive and cost-effective in assessing the global behaviors of a building structure. Only two tri-axial accelerometers are required for a building. One is mounted at the ground level, and another one is mounted at the top floor. First, the relative displacement of top floor to ground is calculated by on-line integration. Then, the diagram of absolute acceleration versus relative displacement of top floor is used to determine the pseudo stiffness of the whole building by linear regression. The decrease of pseudo stiffness denotes the occurrence and degree of damage in the building. A novel real-time damage technique is also proposed to detect nonlinear behavior of a building. A five-story shear-type building under earthquake excitations was illustrated for sensitivity analysis of pseudo stiffness considering different damage cases. Shaking-table-test data of a three-story benchmark building were used to verify the accuracy of the proposed damage assessment technique. In addition, the proposed method was also applied to evaluate a new eight-story residential building equipped with accelerometers in Taipei, Taiwan. Finally, the acceleration response records of a real building, which experienced moderate damages caused by the main shock of 1999 Taiwan Chi-Chi earthquake (ML = 7.3), were considered to examine the applicability of the proposed method to generate a real-time damage indicator for a building with nonlinear behavior. All of the results show that the proposed method is reliable and effective for rapid diagnosis of building health. [ABSTRACT FROM AUTHOR]

Cities with our living spaces; they are seen as the second upheaval after the Neolithic Revolution, accepted as the greatest work of mankind. Cities are constantly changing in motion, and the reading of this change over urban space with the concept of urban morphology dates back to the last century. As a result of the interactions of many disciplines, urban morphology, which has emerged as a new field of study, aims to analyze the changes that a city or a part of the city has undergone by analyzing ıts existing tissue. In particular, these changes that occur due to economic, social conditions or disasters are analyzed with this method. Most of our country is under different earthquake risks. Düzce is also under the influence of the North Anatolian Fault line, which covers the northern part of our country, and two fault zones, which are called with their own name and which can produce severe earthquakes at certain intervals. In this study, the spatial development of the city of Düzce, which is located on the plain of Düzce, which is an old lake bed, has been examined through the economic and planning decisions and the macro form of the city which changed after the disaster. A general evaluation of urban development has been made, starting with the first zoning plan and applications of Düzce. The zoning plans made after the 1999 earthquakes were discussed and the change of the city macro form was examined. [ABSTRACT FROM AUTHOR]

B Correction b : B I Bulletin of Earthquake Engineering i b 21, B 233 (2023) b https://doi.org/10.1007/s10518-023-01638-6 Original article was published with incorrect references and should be read as: Somma F, Flora A, Bilotta E, Viggiani GM (2021b) Numerical analysis on shallow foundations lateral disconnection. The online version of the original article can be found at https://doi.org/10.1007/s10518-023-01638-6. In: 8th ECCOMAS thematic conference on computational methods in structural dynamics and earthquake engineering. [Extracted from the article]

The large number of pulses recorded during the 1999 Mw7.6 Chi-Chi Taiwan earthquake provided an important data for this study. The prediction of near-fault velocity pulses generated by large earthquakes can provide some reference for the Engineering anti-earthquake design. Based on the established source model and velocity structure model, this paper attempts to use the 3D finite difference method to simulate the 39 near-fault large velocity pulses. The conclusions are the following: (1) Two-segment "shovel-like" fault model constructed by 3D bending plane can better describe the characteristics of the underground real fault. (2) The seismic moment and rise time of the six asperities determine the peak and period of the velocity pulse. The asperities located at shallow low angle mainly affect the horizontal pulse components, and the asperities at high angle contribute more to the vertical pulse component. (3) The difference in sliding properties between the north and south ends of the fault causes a difference in the horizontal pulse components, reflecting the characteristics of the fling-step effect and directivity effect. (4) The characteristic period of the velocity response spectrum has the maximum near the turning point at the north end of the fault and shows a very obvious hanging wall effect in the near-fault region, resulting in the large-scale structures having severe damage because of large resonance effect. (5) Peak ground velocity (PGV) gradually increases from south to north along the fault and PGV on the hanging wall is significantly larger than PGV on the footwall, and the distribution of the pulses in front of the rupture is wider than that of the rear. Because the simulation results are basically consistent with the real records, this also verifies the feasibility of simulating pulse-like ground motions with the 3D finite difference method. [ABSTRACT FROM AUTHOR]

We initially assumed that earthquake-induced liquefaction caused the collapses; however, we did not find any surface manifestations - an observation echoed by our Taiwanese colleagues who were in the field immediately after the earthquake. Our analyses will use the data from HVSR testing, ground motions records, supplemental data provided by our Taiwanese colleagues, and liquefaction analysis procedures for ground motions with pulselike directivity effects (e.g., [1]). We recently returned from a post-earthquake reconnaissance trip to Taiwan sponsored by the National Science Foundation-funded Geoengineering Extreme Events Reconnaissance (GEER) Association. [Extracted from the article]