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Shallow‐water hydrothermal vents have gained growing attention for their intricate characteristics caused by various epipelagic factors. The shallow‐water hydrothermal system offshore Kueishan Island, Taiwan, situated in an earthquake‐prone area, has prompted our exploration into the relationship between hydrothermal and seismic activities. Our 2‐yr observation uncovered that the hydrothermal venting entered a silent period in November 2020, followed by a resurgence of activity after September 2021, coinciding with high‐frequency shallow earthquakes occurring within 5 km of the vents. The pH level, dissolved inorganic carbon, alkalinity, pCO2, CO32−, and sulfide served as indicators of hydrothermal activity, contributing to environmental changes in habitats during period transition. However, peering physicochemical and soundscape conditions, distinctions may still arise during two separate active periods. Through multivariate analysis, this study highlights the variability of shallow‐water hydrothermal vents, emphasizing the necessity for more frequent and detailed investigations to further understand these extreme and dynamic marine ecosystems. [ABSTRACT FROM AUTHOR]

The devastating Chichi earthquake in Taiwan in 1999 highlighted the importance of disaster prevention and relief operations. In response to the challenge of extreme events and compound disasters, the National Science and Technology Center for Disaster Reduction (NCDR) contributes to operations at the Central Emergency Operation Center (CEOC) of Taiwan by providing integrated information and timely suggestions, and it delivers a common operational picture to central and local governments through a decision support system. This study was undertaken to explore the emergency response towards the reconnaissance of earthquake disasters in Taiwan to illustrate how resilient cities ensure rapid crisis response with a focus on the NCDR disaster response decision support system. This study examines the decision support system used following the 2016 ML 6.6 Meinong earthquake. The results demonstrate that the first line of relief for the emergency response commander is data-driven decision-making. [ABSTRACT FROM AUTHOR]

This article explores how collective memory of the 1999 Marmara earthquake frames collective thinking of "the expected Istanbul earthquake" through numerous catastrophic earthquake scenarios posted on the prominent Turkish social media platform called Ekşi Sözlük for nearly two decades. The article first integrates memory, media, and disaster studies to theorize how a looming catastrophe is (re)imagined in retrospect. It then analyzes earthquake scenarios using representative samples to illustrate how the oscillatory dynamics and acts of disaster memory shape the future thinking of a not-yet-come threat within a Turkish social media ecology. [ABSTRACT FROM AUTHOR]

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]

This study explores the potential of machine learning algorithms for earthquake prediction, utilizing fluid chemical anomaly data from hot springs. Six hot springs, located within an active fault zone along the southeastern coast of China, were carefully chosen as hydrochemical monitoring sites for an extended period of two and a half years. Using this data, a prediction model integrating six algorithms was developed to forecast M ≥ 5 earthquakes in Taiwan. The model's performance was validated against recorded earthquake events, and the factors influencing its predictive capability were analyzed. Our comprehensive analysis conclusively demonstrates the superiority of machine learning algorithms over traditional statistical methods for earthquake prediction. Additionally, including sampling time in the data sets significantly improves the model's predictive performance. However, it is important to note that the model's predictive performance varies across different hot spring and indicators type, highlighting the importance of identifying optimal indicators for specific scenarios. The model parameters, including the anomaly detection rate (P) and earthquake response time threshold (M), significantly impact the model's predictive capabilities. Therefore, adjustments are needed to optimize the model's performance for practical use. Despite limitations such as the inability to differentiate pre‐earthquake anomalies from post‐earthquake anomalies and pinpoint the precise location of earthquakes, this study successfully showcases the potential of machine learning algorithms in earthquake prediction, paving the way for further research and improved prediction methods. Plain Language Summary: This study explores the potential of utilizing machine learning algorithms for earthquake prediction based on hydrothermal fluid chemical anomaly data. An earthquake prediction model integrating six machine learning algorithms was developed using continuous hot spring hydrochemical monitoring data. The model's prediction performance was validated using actual earthquake event data, and various factors influencing its predictive capability were analyzed. The results demonstrate that the machine learning algorithm's prediction performance exceeds that of traditional methods, and the selection of hot springs, indicator types, and model parameters significantly impacts the model's prediction performance. This study successfully showcased the potential of machine learning algorithms in earthquake prediction, while also indicating new avenues for further research and improvement of prediction methods. Key Points: An earthquake prediction model based on machine learning using hydrochemical data from hot springs is proposed with sufficient accuracyThe earthquake prediction accuracy of the local outlier factor algorithm outperformed the traditional statistical methodThe predictive performance of the model varies across different hot springs, indicators type, and model parameters [ABSTRACT FROM AUTHOR]

The seismicity of the Philippines and Taiwan provides insight into the tectonics and seismic hazards of a region characterized by subduction and collision. We summarize the seismotectonics of the Philippines and Taiwan by documenting the distribution of hypocenters for earthquakes of magnitude M ≥ 4.6 and focal mechanisms for earthquakes of magnitude M ≥ 5.0 over ∼21 years. We quantify seismicity rates (earthquake frequency) and compare seismicity distributions with proposed tectonic and faulting models. 6,187 earthquakes of magnitude M ≥ 4.6 occurred between 1 January 2000 and 31 March 2021, 79% at depths <70 km and 70% having magnitudes M < 5.0. Approximately 88 earthquakes of magnitude M ≥ 5.0 occur per year, with 12 events of magnitude M ≥ 7.0 occurring since January 2000. Seismic activity decreases exponentially between 50 and 210 km depth at a rate ∼10% faster than the global average. Intermediate and deep earthquakes at depths >70 km trace the Wadati‐Benioff zones of subducting slabs, most of which are only seismically active to depths of ∼250 km. The distribution of earthquakes at depths >70 km is likely influenced by the subduction of young lithosphere, slab tearing, and phase boundary interactions between depths of 410 and 660 km. Shallow earthquakes at depths ≤70 km are generated by megathrust, crustal, and intraslab faulting. Crustal thrust and strike‐slip faulting are the most abundant and prevalent sources of damaging earthquakes. The Philippines and Taiwan are subject to high seismic risk, similar to nearby Indonesia. Plain Language Summary: The Philippines‐Taiwan region is tectonically active with frequent earthquakes. We summarize the geographical distribution, sources, and frequency of earthquakes in the region over 21 years, compare distributions to proposed tectonic models, and investigate earthquake hazards. This region experiences on average 88 earthquakes per year of magnitudes ≥5.0. Twelve events of magnitudes ≥7.0 occurred between January 2000 and March 2021. Most earthquake activity is shallow and occurs at depths ≤70 km. In some regions, such as Southern Mindanao in the Philippines, seismicity extends to depths >600 km. Shallow earthquakes are generated by various faulting sources, and seismic hazards are abundant and seismic risk is high, as several population centers are located near active faults. Key Points: We summarize seismotectonics of the Philippines‐Taiwan region using hypocenters, focal mechanisms, seafloor age, and tectonic modelsShallow seismicity is abundant, consisting of thrust, strike‐slip, and normal faulting, which all pose serious seismic hazardsSubduction zone seismicity occurs at depths ∼100–250 km for young (20–40 Ma) oceanic lithosphere, and up to 680 km for older (60–80 Ma) [ABSTRACT FROM AUTHOR]

Between 2 and 3 April 2024, two strong earthquakes occurred in Taiwan, resulting in a significant number of deaths and millions of euros in damage. The primary event also resulted in a tsunami that overwhelmed the population and infrastructure. In this study, the natural electromagnetic spectrum is analyzed a few days before these earthquakes occurred, with the aim of investigating any electromagnetic signals as possible candidates for physical phenomena in the preparatory phases of earthquakes. The signals detected are characterized by very low frequencies, already noted during other potentially destructive earthquakes, and by RDF signals attributable to candidate pre-seismic signals. [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]

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]

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]

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]

Critical infrastructure (CI) is exposed to natural hazards that may lead to the devastation of these infrastructures and burden society with the indirect consequences that stem from this. The vulnerability is a key determinant for understanding, assessing and reducing natural hazard-induced risks to these infrastructures. To date, however, essential vulnerability information for CI is distributed across literature instead of being accessible through a centralized dataset. This study, through a systematic literature review, synthesises the state-of-the-art of fragility and vulnerability curves for CI assets of energy, transport, water, waste, telecoms, health and education in context of natural hazards and offers a unique physical vulnerability database. The publicly available centralized database that contains over 1,250 curves can directly be used as input for risk assessment studies that evaluate the expected or potential damages to assets due to flooding, earthquakes, windstorms and landslides. The literature review highlights that vulnerability development has mainly focused on earthquake curves for a wide range of infrastructure types. Windstorms have the second largest share in the database, but are especially limited to energy curves. While all CI systems require more vulnerability research, additional efforts are needed for telecommunication which is largely underrepresented in our database. [ABSTRACT FROM AUTHOR]

Resilience in the face of crises is crucial for minimizing the impact of disasters and enabling rapid recovery. This study delves into the interlinked consequences of two seismic events that significantly impacted Türkiye in 1999 and 2023. Using an impact chain analysis, the aim is to provide a thorough understanding of the extensive effects on structures, infrastructure, and socio-economic dynamics. The research also examines the evolution of disaster management practices from the 1999 Kocaeli Earthquake to the more recent seismic events in 2023, highlighting advancements in risk management and resilience. Both seismic events revealed vulnerabilities in the construction of buildings, emphasizing seismic shortcomings that led to widespread damage. Earthquakes exert a profound impact on critical infrastructure, affecting transportation, communication, and energy systems, with cascading effects that extend to the broader socio-economic landscape. The effectiveness of the methodology, particularly, the impact chain analysis, is emphasized as it reveals complex causal relationships. Visual representations support effective communication and collaboration among stakeholders, offering a holistic perspective on systemic risks. In conclusion, this study contributes to understand disaster resilience and provides a foundation for subsequent research, policy formulation, and pragmatic strategies for disaster preparedness and response. [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]

The North Anatolian Fault Zone (NAFZ), which produced the 1999 Golcuk-Izmit earthquake, extends in three branches in the Marmara Region and causes a significant earthquake hazard. This study consists of processing and analysing data from three stations (TUBI, MER1 and DUMT) that are part of the IGS and MAGNET (Marmara Permanent GPS Network) network and are situated close to the epicentre of the Golcuk-Izmit earthquake. By analysing the time series generated from three daily solutions (TUBI, DUMT and MER1 stations), the displacements due to the earthquake were computed (17 August 1999). When GPS processing on 15–16 August 1999, especially for the Golcuk-Izmit earthquake, is examined, it is possible to interpret this situation as a precursor of the earthquake, as a result of the examination of the data obtained from the process of 15 and 16 August 1999. On August 17, 1999, the movement at the TUBI, DUMT and MER1 points before the earthquake was 2–6 cm while it was computed on average 38–86 cm during and after the earthquake. The earthquake clearly had substantial impact on the horizontal components on 17 Aug 1999. The horizontal coordinates of TUBI, DUMT and MER1 stations have changed by around 49–87 cm, and the height components have changes by around 14–137.10 cm based on the time series of coordinate discrepancies. [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]

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]

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]

A major portion of the cultural heritage consists of old structures that are susceptible to earthquakes. These structures are prone to significant damage from natural disasters, particularly earthquakes. This study's primary goal is to assess the historical masonry bridge's seismic response to strong far-fault ground motions (FFGM) and near-fault ground motions (NFGM). The historical Sultan Suyu Masonry Bridge is used as a case study in this study. It was created with three-dimensional finite element software. The time history response of the bridge model is contrasted with one another in terms of stresses and displacements produced for FFGM and NFGM. The assessments take into account the FFGM and NFGM of the 1999 Düzce, 1999 Kocaeli, and 1992 Erzincan earthquakes, which had nearly equal peak ground accelerations. The results show that FFGM is equally significant as NFGM and that FFGM could be used in conjunction with NFGM to further evaluation of historical masonry arch bridges. [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]

We examined the stratigraphy of alluvial fans formed at the steep range front of the Southern Alps at Te Taho, on the north bank of the Whataroa River in central West Coast, South Island, New Zealand. The range front coincides with the Alpine Fault, an Australian‐Pacific plate boundary fault, which produces regular earthquakes. Our study of range front fans revealed aggradation at 100‐ to 300‐year intervals. Radiocarbon ages and soil residence times (SRTs) estimated by a quantitative profile development index allowed us to elucidate the characteristics of four episodes of aggradation since 1000 CE. We postulate a repeating mode of fan behaviour (fan response cycle [FRC]) linked to earthquake cycles via earthquake‐triggered landslides. FRCs are characterised by short response time (aggradation followed by incision) and a long phase when channels are entrenched and fan surfaces are stable (persistence time). Currently, the Te Taho and Whataroa River fans are in the latter phase. The four episodes of fan building we determined from an OxCal sequence model correlate to Alpine Fault earthquakes (or other subsidiary events) and support prior landscape evolution studies indicating ≥M7.5 earthquakes as the main driver of episodic sedimentation. Our findings are consistent with other historic non‐earthquake events on the West Coast but indicate faster responses than other earthquake sites in New Zealand and elsewhere where rainfall and stream gradients (the basis for stream power) are lower. Judging from the thickness of fan deposits and the short response times, we conclude that pastoral farming (current land‐use) on the fans and probably across much of the Whataroa River fan would be impossible for several decades after a major earthquake. The sustainability of regional tourism and agriculture is at risk, more so because of the vulnerability of the single through road in the region (State Highway 6). [ABSTRACT FROM AUTHOR]

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Faults often form through reactivation of pre-existing structures, developing geometries and mechanical properties specific to the system's geologic inheritance. Competition between fault geometry and other factors (e.g., lithology) to control slip at Earth's surface is an open question that is central to our knowledge of fault processes and seismic hazards. Here we use remote sensing data and field observations to investigate the origin of the 2019 M7.1 Ridgecrest, California, earthquake rupture geometry and test its impact on the slip distribution observed at Earth's surface. Common geometries suggest the fault system evolved through reactivation of structures within the surrounding Independence dike swarm (IDS). Mechanical models testing a range of fault geometries and stress fields indicate that the inherited rupture geometry strongly controlled the M7.1 earthquake slip distribution. These results motivate revisiting the development of other large-magnitude earthquake ruptures (1992 M7.3 Landers, 1999 M7.1 Hector Mine) and tectonic provinces within the IDS. Faults responsible for the 2019 M7.1 Ridgecrest, California earthquake likely evolved through reactivation of pre-existing Independence dike swarm structures. The inherited rupture geometry strongly controlled the earthquake slip distribution. [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 Bosphorus Suspension Bridge, which connects the Asian and European sides, has a geopolitical importance in terms of its location, and has also been integrated with Istanbul. The bridge has a main span of 1074 m, and it had inclined hanger configuration until recently. On January 2004, a hanger-to-deck connection close to European side tower was damaged due the storm. This resulted in discussion of changing the inclined hangers with vertical ones. Inclined hangers increase the aerodynamic stability of the bridge; however some of them can remain as slack and easily swing under wind load. This occurred at the Bosphorus Suspension Bridge. On July 2015, the inclined hangers were replaced with vertical ones. This study aim to investigates changing of hanger configuration on the structural behavior of the Bosporus Suspension Bridge. When the suspensions of an inclined designed bridge are later changed vertically, the changes that occur in the other carrier elements of the bridge (tower, deck, cable, etc.) are examined and interpreted, and how the existing unchanged other carrier system of the bridge is affected by this change has been investigated. For this aim, three-dimensional finite element analyses were employed for both inclined and vertical hanger configurations. Modal, static and dynamic analyses were practiced by considering geometrical nonlinearity. At the end of the analyses, dynamic characteristics, displacements and internal forces were obtained and presented in detail. The GBZ000 component of Gebze station records of 1999 Kocaeli earthquake is utilized as a ground motion for dynamic analysis. From the analyses, it was evident that the vertical hanger configuration had a positive effect on the bridge response in terms of vertical displacement and internal forces obtained. Also, it was seen that all hangers were loaded as equal in the event of vertical configuration and this made the bridge more stable. Based on these, the vertical hanger configuration is recommended in terms of more safety. [ABSTRACT FROM AUTHOR]

Natural disasters have some environmental impacts as well as economic impacts. For example, when disasters such as earthquakes are not prevented, efforts must be made to minimize the economic and environmental costs that may arise. Although the interest of society and governments in the economic consequences of the earthquake is more intense, environmental effects should also be calculated, and the significance of the situation should be shown. Herein, it estimated the CO2 emissions caused by debris transport from the 1999 Marmara earthquake in Turkey in Yalova, a province of Turkey, and the reconstruction of the destroyed structures. As a result of the calculations, it has been found that 2031 x 103 tons of CO2 were released during the transport of debris and reconstruction of 9462 building that was destroyed before the end of their life in Yalova. Moreover, 42% of these emissions are caused by concrete alone. In addition, this value corresponds to 0.73% of the CO2 emitted in Turkey in 1999. [ABSTRACT FROM AUTHOR]

Sustained coseismic changes in groundwater level due to static strain during earthquakes could be considered as an indicator of crustal deformation. These changes usually occur abruptly but recover slowly after earthquakes. High-frequency data indicate a time lag between the coseismic change of well water levels and that of the groundwater levels in the aquifer. Abnormal post-seismic changes in groundwater level were observed, possibly caused by cross-formation flow, fracturing, or strain relief. Although sustained changes are generally induced by a local earthquake, they could also be triggered by a distant large earthquake that has occurred at the same tectonic plate. The magnitude and polarity of coseismic changes may vary in wells of different depths at multiple-well stations, revealing additional information about the complexity of crustal deformation in the subsurface. Coseismic falls dominated near the ruptured seismogenic fault during the 1999 M7.6 earthquake, which implied crustal extension adjacent to the thrust fault. However, coseismic rises prevail in most areas, suggesting that crustal compression caused by plate convergence plays a major role on the island of Taiwan during earthquakes. [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]

An earthquake of magnitude 6.4 occurred in Yangbi County, Yunnan Province on 21 May 2021, with a focal depth of 8 km, and strong ground motion with vertical components was monitored by Yangbi station (53YBX). A total of 14,122 houses were damaged in Yangbi in the earthquake, and 232 of them collapsed. Vertical components of ground motions have been gained more attention for its effect on structure's seismic response in epicenter or near-fault regions at present. Taking the three earthquake ground motions of Yangbi, Chi-Chi, and Loma Prieta as inputs, and modeling based on Perform-3D, this research carried out the seismic dynamic time history analysis of an RC (reinforced concrete) frame structure and a brick-concrete structure under both horizontal and vertical working conditions. The results showed that vertical components of the three ground motions had no evident impact on the top horizontal displacement and acceleration of the two types of structures. Among the three ground motions, the vertical component of Yangbi ground motion has largely influenced the top vertical displacement, acceleration, and axial force of the frame column bottom (or masonry wall bottom). The vertical component had different amplification effects on the axial pressure and the bending moment of a single column at the bottom of the RC frame structure, thus causing resonance amplification effect of the brick-concrete structure floors and amplifying the vertical acceleration of the top floor. In addition, it considerably increase the maximum axial tensile strain of masonry walls and the possibility of faster tensile failure of the brick-concrete structure. Influence of vertical ground motion on the bearing capacity of RC frame structure's columns and the brick-concrete structure's masonry walls should not be ignored. The results of the research may provide a reference for the earthquake-resistant design of building structures, especially the earthquake-resistant design considering the vertical seismic effect. [ABSTRACT FROM AUTHOR]

Research in earthquake engineering heavily relies on strong motion observation. The quality of strong motion records directly affects the reliability of earthquake disaster prevention, rapid reporting of seismic magnitude, earthquake early warning, and other areas. Currently, basic mathematical methods, such as zero-line adjustment and filtering, are commonly employed to ensure the quality of strong motion records. However, these methods often rely on subjective judgment based on human experience when dealing with abnormal waveforms in strong motion records, leading to relatively low efficiency. To address this challenge, this paper proposes an innovative Transformer model based on Bayesian optimization to efficiently identify baseline drift anomalies in strong motion records. By partitioning the strong motion record data from the 1999 Chi-Chi earthquake in Taiwan, China, into two categories: high-quality records (with minimal baseline drift) and low-quality records (with significant baseline drift), we extracted data with distinct features and inputted them into the proposed model for training. Data with distinct features were extracted and input into the proposed model for training. Finally, the model was used to predict whether strong motion records exhibited baseline drift abnormalities. The experimental results show that the optimized Transformer model achieves a performance exceeding 85% in key evaluation metrics such as accuracy and F1 scores. It is capable of efficiently identifying a substantial volume of strong motion records with baseline drift within a short period of time. The model effectively performs the baseline drift classification task for strong motion records and can be used for subsequent identification of abnormalities after baseline drift correction, enabling automation in handling abnormal data related to baseline drift. [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]

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]

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]

During the Last Glacial Maximum (LGM) (~20,000 years ago), the sea level was lower than that during the present day by 120 m and the heads of most submarine canyons were close or connected to the coastline or shore, with enhanced terrestrial sediment input due to direct connections with river mouths. This was followed by a relative sea-level rise of 120 m and the migration of coastlines landward. As a result, the heads of some paleo-submarine canyons were no longer near river mouths or connected to the shore. Such canyons became inactive due to the lack of terrestrial sediment input. Only 4% of the world's submarine canyons reach the coastline and remain active today. Among 13 submarine canyons off the shore of Taiwan, we identified seven (n = 7, 54%) that remain connected to the shore and are active during the present-day highstand. The purpose of this study is to determine the key controls of canyon heads that remain connected to the shore with terrestrial sediment input during the Holocene sea-level rise. As a result of high uplift rates, narrow coastal range, steep gradients, frequent earthquakes, and typhoon development in the Taiwan mountain belt, Taiwan has the highest-yield river and sediment supply. This has led to the transportation of large volumes of sediment to the surrounding deep seas. Narrow steep shelves and large sediment volumes associated with small mountain rivers are the main controls involved in the development of shore-connected canyons on the active Taiwan margin. Shore-connected canyons are present in greater numbers in the major earthquake zone on the eastern Taiwan margin. Frequent earthquake events are another significant factor in the occurrence of shore-connected canyons in the Taiwan region. [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]

Geoelectric time series (TS) has long been studied for its potential for probabilistic earthquake forecasting, and a recent model (GEMSTIP) directly used the skewness and kurtosis of geoelectric TS to provide Time of Increased Probabilities (TIPs) for earthquakes in several months in future. We followed up on this work by applying the Hidden Markov Model (HMM) on the correlation, variance, skewness, and kurtosis TSs to identify two Hidden States (HSs) with different distributions of these statistical indexes. More importantly, we tested whether these HSs could separate time periods into times of higher/lower earthquake probabilities. Using 0.5-Hz geoelectric TS data from 20 stations across Taiwan over 7 years, we first computed the statistical index TSs, and then applied the Baum-Welch Algorithm with multiple random initializations to obtain a well-converged HMM and its HS TS for each station. We then divided the map of Taiwan into a 16-by-16 grid map and quantified the forecasting skill, i.e., how well the HS TS could separate times of higher/lower earthquake probabilities in each cell in terms of a discrimination power measure that we defined. Next, we compare the discrimination power of empirical HS TSs against those of 400 simulated HS TSs, then organized the statistical significance values from these cellular- level hypothesis testing of the forecasting skill obtained into grid maps of discrimination reliability. Having found such significance values to be high for many grid cells for all stations, we proceeded with a statistical hypothesis test of the forecasting skill at the global level, to find high statistical significance across large parts of the hyperparameter spaces of most stations. We therefore concluded that geoelectric TSs indeed contain earthquake-related information, and the HMM approach to be capable at extracting this information for earthquake forecasting. [ABSTRACT FROM AUTHOR]

Earthquakes as a natural hazard have caused substantial economic losses and human life loss in many countries. Taiwan, which is located on the western Circum-Pacific seismic belt, encountered this problem in the form of the Meishan, Hsinchu-Taichung, and Chi-Chi earthquakes a few years ago. In this paper, the researchers propose a novel robot-event integrated system capable of doing the automated inspection and emergency response due to a significant earthquake. As the household's earthquake warning receiving device picks up an alert, its built-in wireless communications system will send a signal to the robot. The robot will then commence the inspection of the indoor area via real-time image recognition and tracking. Upon detecting fallen people, it will approach them, regulating their movements via the robot operating system monitoring interface. The robot is designed to operate in a house that remains standing with acceptable damage in which the furniture might be falling and injure the occupants after an earthquake hit. The indoor experiment was conducted to verify the robot system and operation with a designed condition such as fallen and non-fallen people as the detected object. The precision of the robot arm was tested in the case of the delivery of supplies to the fallen people while waiting for the rescuers to arrive. The tests indicated that the proposed smart robot has prospective implementation in real-world applications with more research and development. The smart robot integrated with an earthquake early warning system is a promising approach to the temporary care of people affected by earthquakes. [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]

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]

In Taiwan, the main purpose of earthquake fault zone legislation is to prevent earthquake-related disasters around the surface traces of active faults, particularly in urban areas. Here, the Geologically Sensitive Area (GSA) of the Milun Fault (Milun Earthquake Fault Zone) is used as an example to reveal the importance of such legislation. Field data collected along the Milun Fault before and after the 2018 Hualien Earthquake were used to reveal the reappearance of damages within the GSA. The 2018 Hualien Earthquake represents one of the shortest recurrence intervals (67 years) among all major faults in Taiwan. Most of the surface ruptures and damaged buildings in Hualien City were within the Milun Fault GSA and concentrated on the hanging wall of the fault. Moreover, 61% (91/148) of the damaged buildings and 83% (692/835) of the surface ruptures occurred within 100 m of the fault line. The results of this study demonstrate the importance of defining GSAs of active faults for mitigating earthquake hazards. [ABSTRACT FROM AUTHOR]

Frequent earthquakes have brought enormous life and property losses to Taiwan Island, and thus reliable earthquake forecasts are valuable. We form 20 tectonics-based shallow earthquake forecasts of Taiwan Island for the years 2019 and after, each with a different threshold moment magnitude, ranging from 5.45 in steps of 0.05 up to 6.40. Our results suggest that Taiwan Island may experience about 25 Mw ≥ 6.25, 40 Mw ≥ 6.00, 65 Mw ≥ 5.75 and 106 Mw ≥ 5.50 shallow earthquakes every 100 years. We demonstrate the consistency between the forecast results and the seismic catalog used for the forecasts and carry out retrospective tests against the seismic catalogs of Taiwan Island not used in the forecasts, which show higher forecast success relative to previous studies of global earthquake forecasts. We identify three gaps of Mw ≥ 6.40 shallow earthquakes, located in Yilan County, Hualien County and Taitung County. We find a general negative correlation between our Mw ≥ 6.40 shallow earthquake forecast and the population density distribution in Taiwan Island. However, we emphasize that the regions with relatively low forecast values need special attention, because these regions generally have relatively high population densities but may also experience strong earthquakes. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to compare the static and dynamic behavior of a historical single-span masonry arch bridge under different near-fault earthquakes. The historical Tokatlı Bridge, built in Karabük, is chosen for this study. To investigate the behavior of near-fault earthquakes on the historical masonry bridge, first, a finite element model is built and analyzed under various near-fault earthquakes by using ANSYS and SAP2000. To build a finite element model, 162920 nodes and 47818 elements are used in ANSYS. First, finite element analysis results are compared to each other under Earth gravity. Then, ground motions near the fault are chosen to be used in this study. These earthquakes can be listed as follows: Cape Mend (1992), Kobe (1995), Superstition Hills (1987), Northridge (1994), Imperial Valley (1979), and Chi-Chi (1999). The behavior of the single-span historical bridge is obtained under these ground motions, and the results are compared with each other using contour diagrams using ANSYS. Furthermore, at the end of these analyses, it is observed that the tensile stresses have reached the permissible masonry tensile strength, especially on the upper side of the large belt, on the upper side of the belt, and on the side of the belt, and pose a risk for damage. [ABSTRACT FROM AUTHOR]