Historical Earthquakes Research Articles

Physics-based assessment of earthquake potential on the Anninghe-Zemuhe fault system in southwestern China

The seismic hazard of a fault system is controlled by the maximum possible earthquake magnitude it can host. However, existing methods to estimate maximum magnitudes can result in large uncertainties or ignore their temporal evolution. Here, we show how the maximum possible earthquake magnitude of a fault system can be assessed by combining high-resolution fault coupling maps with a physics-based model from three-dimensional dynamic fracture mechanics confirmed by dynamic rupture simulations. We demonstrate the method on the Anninghe-Zemuhe fault system in southwestern China, where dense near-fault geodetic data has been acquired. Our results show that this fault system currently has the potential to generate Mw7.0 earthquakes with maximum magnitudes increasing to Mw7.3 by 2200. These results are supported by the observed rupture extents and recurrence times of historical earthquakes and the b values of current seismicity. Our work provides a practical way to assess the earthquake potential of natural faults.

Probabilistic seismic hazard analysis for the Dominican Republic

The Dominican Republic experiences moderate to high seismic hazard mostly caused by oblique convergence at the Caribbean/North American plate boundary that manifests as subduction zones, less-pronounced subduction-like trenches with thrust faulting, long strike-slip faults parallel to the plate boundary, and onshore deformation. Historical earthquakes have damaged the Dominican Republic’s large cities and those in neighboring Haiti, once requiring relocation. Given this, the Dominican Republic joined the “Training and Communication for Earthquake Risk Assessment” (TREQ) project funded by the United States Agency for International Development, which aimed to increase earthquake risk assessment capacity in Latin American cities. The TREQ project was the basis for developing an openly available probabilistic seismic hazard model for the Dominican Republic. The input model was developed from two main datasets: a homogenized earthquake catalog and an active faults database that combines results of recent local projects with a global database. The seismic source characterization used these to constrain source geometries and occurrence rates for active shallow crustal earthquakes, subduction interfaces and subduction-like thrusts, and intraslab earthquakes. Shallow crustal earthquakes, including those on subduction-like thrusts, are modeled by smoothed seismicity and fault sources, the latter using pre-defined geometries that permit multi-fault ruptures. Seismicity on the Puerto Rico Trench subduction interface is modeled as a fault source, while intraslab sources use pre-defined gridded ruptures inside the intraslab volume. The source characterization applies epistemic uncertainties to modeling assumptions affecting occurrence rates and maximum magnitudes. The ground motion characterization used residual analyses from past regional projects as a basis, updating some components with more recent ground motion models. Computed hazard results reinforce those from recent studies in terms of geographical hazard patterns and levels. For 475-year return periods, peak ground acceleration (PGA) in Santiago de los Caballeros reaches 0.50 g, controlled by the Septentrional Fault, while all tectonic region types contribute to the PGA 0.31 g computed for Santo Domingo.

Tectonic geomorphology and paleoseismology of the Angelochori fault segment of the Anthemountas extensional detachment fault, Central Macedonia, Greece: Paleoseismic evidence from the 1677 CE earthquake

This study presents the results of a geomorphological and paleoseismological investigation on the Angelochori normal fault. This fault controls the southern boundary of the Anthemountas basin and constitutes the western segment of the Anthemountas extensional detachment fault (AEDF), a ∼48 km-long, E-W-trending, north-dipping low-angle normal fault in Central Macedonia, Greece. To assess the relative tectonic activity of the Angelochori fault and to determine the number, timing, and displacement of surface-faulting earthquakes, we conducted detailed field mapping and paleoseismological investigations. Our approach involved utilizing geomorphic indices, analyzing stratigraphic and structural relations, considering luminescence ages, and employing OxCal modeling techniques. The acquired data reveal, for the first time, the Middle-Late Holocene activity of the Anghelochori fault, providing constraints on the age of three strong (M > 6) surface-rupturing earthquakes over the last ∼7.7 ka. The youngest of these events aligns with the historical earthquake of the Anthemountas basin in 1677 CE. The observed minimum displacement per event ranges from 0.48 m to 0.65 m, consistent with a fault length estimated at about 24–28 km, suggesting an earthquake magnitude on the order of 6.6. The cumulative slip rate over the recorded period averages 0.21 ± 0.02 mm/a, with an average open recurrence interval of 2.6 ± 0.2 ka. Nonetheless, the displacement pattern displays alternating intervals of rapid slip at 0.60 ± 0.16 mm/a and slower slip at 0.08 ± 0.01 mm/a. Classified as Class 1, the Angelochori fault signifies an active tectonic structure posing a significant seismic hazard for the Thessaloniki metropolitan area.

CFTIlandslides, Italian database of historical earthquake-induced landslides

Knowing the location, the extent and the characteristics of any earthquake-induced environmental phenomenon is becoming an increasingly pressing need for civil protection agencies and local administrations. In particular, earthquake-triggered landslides are known for being among the most important sources of secondary hazard, as they may cause significant losses and may delay rescue operations across large areas. The combination of the relatively frequent seismic release with a very high landslide susceptibility makes the Italian territory especially prone to the occurrence of earthquake-induced landslides. The CFTIlandslides dataset features over 1,000 landslides triggered by historical Italian earthquakes (up to 1997). The landslides effects are subdivided into classes based on location accuracy and type of movement. Knowing the distribution of the past earthquake-induced landslides provides the input information for assessing the related hazard. This dataset is addressed to a large audience of potential users, including researchers and scholars, administrators and technicians belonging to local institutions, and civil protection authorities.

Frictional Properties of Natural Granite Fault Gouge Under Hydrothermal Conditions: A Case Study of Strike‐Slip Fault From Anninghe Fault Zone, Southeastern Tibetan Plateau

AbstractThe Anninghe Fault (ANHF) is a major left‐lateral strike‐slip fault in southwestern China and one of the main seismogenic fault zones with a history of strong earthquakes. To understand the frictional properties of natural granitic gouges from the principal slip zone, we conducted hydrothermal friction experiments using both saw‐cut and ring shear methods. These experiments were performed at temperatures (T) of 25–600°C, pore pressures (Pf) of zero (dry), 30 and 100 MPa, sliding velocities (V) of 0.01–100 μm/s and effective normal stresses () of 68, 100, and 200 MPa. The (apparent) friction coefficient is low (μ < 0.5) at high T (600°C), high Pf (100 MPa) and low V (<1 μm/s); but high (μ > 0.6) under all other T, Pf and V conditions. Under high Pf, the velocity dependence of friction, (a‐b), displays three regimes with increasing temperature, from positive below ∼100°C to negative at 100–300°C (at V = 1–3 μm/s) or else 100–450°C (at V = 30–100 μm/s), becoming positive again above 300–450°C. At low Pf, the negative (a‐b) expands to the range ∼300–600°C. Microstructural observations and microphysical interpretation imply that the frictional weakening and transitions in (a‐b) are related to competition between dilatant granular flow and deformation of the fine‐grained gouge by intergranular pressure solution accompanied by healing phenomena (leading to cavitation‐creep‐like behavior). Our results provide a possible explanation for the distribution of earthquakes at different depths in the continental crust, in particular for the depth range of the seismogenic zone between 4 and 24 km along the ANHF.

Resolving the Location and Magnitude of the 1918 Queensland (Bundaberg), Australia, Earthquake

ABSTRACT Eastern Queensland (Australia) was struck by a major earthquake at ≈04:14 a.m. local time on 7 June 1918. Most previous studies have suggested that the epicenter of this earthquake lies off the coast of Bundaberg, between the port cities of Gladstone and Rockhampton. This epicentral location was based upon instrumental observations from the Riverview College observatory in Sydney. However, this epicenter lies ≈250 km to the northeast of an inland region that experienced both the strongest shaking effects and numerous felt aftershocks. We revisited available macroseismic data from 224 geographic locations and surviving instrumental observations for the 1918 Queensland earthquake to show that the most likely epicentral location was inland at ≈24.93° S and ≈150.88° E in the Banana Shire and North Burnett region. The re-estimated instrumental magnitude of Mw 6.0 ± 0.3 (1σ) makes it one of the largest onshore earthquakes in eastern Australia in the past century. Our observations also offer support for a viewpoint proposed in 1935 by an eminent Queensland geologist, Walter Heywood Bryan, that the 1918 earthquake was inland. Our study highlights the benefit of the critical evaluation of primary source materials, both archival and seismological, to study historical earthquakes in Australia that are relevant for modern seismic hazard analysis.

Seismicity and Tectonics of the Republic of Kosovo

Abstract Kosovo is distinguished by a particularly high degree of seismic activity as a result of its location in the alpine-Mediterranean seismic area. The thickness of the seismic zone in the Earth’s crust is a crucial element in seismotectonics, as it affects the design of fault systems, relative fault activity, earthquake size and distribution within a fault system, and the long-term accumulation of tectonic deformation. Kosovo’s large depressions and high relief make it challenging geomorphologically. The country of Kosovo is divided into numerous chunks along the fault lines because of the inclinations of these prevalent motions. Normal faults, along which differentiations on the order of 2000 m occurred during the neotectonics period, identify the contacts between these blocks. Understanding Kosovo’s seismotectonic characteristics requires an exact analysis of hypocenter parameters when historical earthquakes that have struck the country are reassessed for magnitude. This study deals with the seismicity and tectonics of the territorial space of the Republic of Kosovo.

Estimating S-wave amplitude for earthquake early warning in New Zealand: Leveraging the first 3 seconds of P-Wave

This study addresses the critical question of predicting the amplitude of S-waves during earthquakes in Aotearoa New Zealand (NZ), a highly earthquake-prone region, for implementing an Earthquake Early Warning System (EEWS). This research uses ground motion parameters from a comprehensive dataset comprising historical earthquakes in the Canterbury region of NZ. It explores the potential to estimate the damaging S-wave amplitude before it arrives, primarily focusing on the initial P-wave signals. The study establishes nine linear regression relationships between P-wave and S-wave amplitudes, employing three parameters: peak ground acceleration, peak ground velocity, and peak ground displacement. Each relationship’s performance is evaluated through correlation coefficient (R), coefficient of determination (R²), root mean square error (RMSE), and 5-fold Cross-validation RMSE, aiming to identify the most predictive empirical model for the Canterbury context. Results using a weighted scoring approach indicate that the relationship involving P-wave Peak Ground Velocity (Pv) within a 3-second window strongly correlates with S-wave Peak Ground Acceleration (PGA), highlighting its potential for EEWS. The selected empirical relationship is subsequently applied to establish a P-wave amplitude (Pv) threshold for the Canterbury region as a case study from which an EEWS could benefit. The study also suggests future research exploring complex machine learning models for predicting S-wave amplitude and expanding the analysis with more datasets from different regions of NZ.

Behind the Italian catalogues: overlooked but far from negligible earthquakes

The Italian parametric earthquake catalogue is the result of several decades of historical seismological research, based in its turn on a centuries-long tradition of descriptive earthquake compilations. Thanks to historical seismological research undertaken since the mid-1980s, knowledge of the major historical earthquakes in Italy has hugely improved. These studies, however, focused mainly on earthquakes already recorded in Mario Baratta’s extensive compilation I terremoti d’Italia (a summary of earlier descriptive earthquake studies, published in 1901), rather than on the identification of earthquakes still ‘unknown’ to the Italian seismological tradition. As the results of a systematic perusal of ‘serial’ historical sources show, it is still possible to discover locally significant earthquakes (i.e. important for improving seismic history and hazard assessment of given localities or areas) that no previous studies had ever considered. Initiating new research projects specifically aimed at the identification of earthquakes unknown to the seismological tradition is therefore essential to improve hazard assessments on a subregional and local level.

Imaging the Fault Plane Structure of Palu-Koro Fault from Earthquake Data Using Python

Abstract Palu-Koro Fault is one of the active faults located in Sulawesi and positioned in the middle of the Island, dividing the west and east-southeast arms. Its long history of earthquakes provides sufficient focal mechanisms data to be analyzed. This research used seven focal mechanism data of shallow magnitude earthquakes surrounding the pull-apart basin area of the Palu-Koro Fault. The focal mechanism data used is secondary data obtained containing the information needed. This research aims to create a 3D model of the pull-apart basin displaying the geometries of the fault planes and providing a closer look at the fault system surrounding the bounding fault zones. Python script was made to classify the mechanism of each earthquake based on its correlation to the trend of the Palu-Koro Fault. Nodal planes are categorized as whether it is presumed to be the fault plane or the auxiliary plane of the focal mechanism. The result found that not all earthquake data was classified through the assumed parameter set. Only five of seven earthquake data managed to be classified, while the rest showed a different focal mechanism. It is found from the python script created revealed the presence of three fault types: normal fault, normal left lateral oblique fault, and left lateral strike-slip. The 3D fault plane interpolation showed two distinct dipping directions, suggesting their association with the basin’s bounding fault, either the west or the east side. From the gathered information, previous research, and geological interpretation, the earthquake data can be concluded into three fault associations to the bounding fault: synthetic extension fault, antithetic extension fault, and sinistral strike-slip fault.

3D shear wave velocity and azimuthal anisotropy structure in the shallow crust of Binchuan Basin in Yunnan, Southwest China, from ambient noise tomography

The Binchuan Basin in northwest Yunnan, southwest China, is a rift basin developed at the intersection of the Red River Fault and Chenghai Fault, where historical earthquakes have occurred. Understanding the fine velocity structure of the shallow crust in this region can help improve earthquake location accuracy and our understanding of the relationship between fault zone structures and fault slip behaviors. Using the continuous waveform data recorded by 381 dense array stations in 2017, we obtained 7 915 Rayleigh-wave phase velocity dispersion curves in the period band of 0.2–6 ​s from ambient noise cross-correlation functions after rigorous data processing and quality control. We determined 3D isotropic and azimuthally anisotropic shear wave velocity models at depths above 6 ​km in the shallow crust based on the direct surface wave azimuthal anisotropic tomography method. The isotropic model reveals a strong correspondence between the S-wave velocity structure at depths of 0–1 ​km and the regional topography and lithology. The Binchuan depocenter, Zhoucheng depocenter, Xiangyun Basin, and Xihai Rift Basin are primarily composed of Quaternary deposits, which show low-velocity anomalies, while the regions with the Paleozoic shale, limestone, and basalt exhibit high-velocity anomalies. The nearly N–S orientation of fast directions from azimuthal anisotropy models are mainly controlled by the active Binchuan Fault with N–S strike as well as the NNW-oriented primary compressive stress.

<p>A Catalogue of Historical and Instrumentally-Recorded M<sub>s</sub> ≥ 7 Earthquakes in Taiwan</p>

A catalogue of forty-nine instrumentally-recorded earthquakes with magnitudes ≥ 7 in Taiwan from 1906 to date is compiled from regional and international catalogues and literature. Included also are seven historical earthquakes that occurred from 1792 to 1867. The earthquake magnitude is the surface-wave magnitude, Ms. The moment magnitude, Mw, is also evaluated either from Ms or obtained from related documents. Except for one event, Mw is smaller than or equal to Ms. There are the ‘doublets’, ‘triplets’, and ‘quadruplets’ in these earthquakes. The spatial distribution of epicenters shows that most of the events occurred in offshore eastern Taiwan and only a few inland events happened in western Taiwan. The shortest inter-occurrence time between two consecutive events is less than 1 day; while the longest one is 5742 days between No. 47 event and No. 48 event. The inter-occurrence time somewhat increases with time. The time series of earthquakes shows irregular recurrence behavior with aperiodicity, fractality, and a weak memory effect. The damage produced by earthquakes is much higher from inland events (mainly in western Taiwan) than from offshore ones.

First luminescence dating of exhumed fault-zone rocks of the North Tehran Fault, Iran

Here we report luminescence dating results on exhumed fault rocks from the North Tehran Fault (NTF, Iran), including the fault gouges. The NTF is an oblique-dip thrust fault expanding from west to east at the northern fringe of the megacity of Tehran. Although the fault is known to be active and a major threat to the city, only little is known about its earthquake history. We present first data on the timing of past fault motion using dating of fault rocks. Three sites have been selected for this study in which the fault damage zone is associated with Eocene volcaniclastic rocks (Karaj Formation). The fault gouge, transitional and damage zone were sampled for which we observed slip planes in the field. The fault rocks are composed of quartz and alkali feldspar favourable for luminescence dating. However, our study reveals that the quartz optically stimulated luminescence (OSL) signal of the Karaj Formation does not seem to have a measurable fast decaying signal component. Instead, the post-infrared stimulated luminescence at 225 °C (pIRIRSL225) of polymineral fine-grain fraction appears to be the most feasible signal for these samples. The first luminescence-based results presented here comprise an age range from 45 ± 5 ka to 72 ± 13 ka for fault gouges and transitional zone. Since dating the transitional zone close to the fault gouge led to a younger age than the fault gouge at one site, we conclude that the sampling location plays a crucial role in dating exhumed fault rock using luminescence dating. The obtained ages are far older than those of the previous palaeoseismological studies that dated earthquake-related sedimentary features in the region. Therefore, more research is required to shed light on the resetting mechanism and condition of these fault rocks due to the recent activity of the NTF.

Analysis and Statistical Assessment of Liquefaction Potential Using SPT-N Approach in Bhandara Region Maharashtra: Implications for Infrastructure Development

The Bhandara area in Maharashtra, India, has a lot of earthquakes, so its liquefaction potential needs to be studied in detail to help with building infrastructure. This research uses the Standard Penetration Test (SPT-N) method to check how easily the dirt in the area can become liquefied. When SPT-N numbers are added to soil qualities and seismic factors, they are used to figure out how likely it is that the ground will liquefy when it is loaded with earthquake energy. Different types of dirt and different levels are more or less likely to liquefy, according to the results. The makeup of the soil, the level of the groundwater table, and the history of earthquakes are some of the most important things that affect the liquefaction potential. The study finds places where there is a high risk of liquefaction that are also expected to have big building projects. These results make it clear how important it is to include liquefaction mitigating measures when designing and building roads, houses, and other important infrastructure to make sure it is safe and strong. The study also gives a plan for future earthquake risk ratings in the area, showing how important it is to keep an eye on and update records of soil data and earthquakes. Using the SPT-N method along with current geotechnical and earthquake analysis methods, this study gives a full picture of the area's liquefaction risk. The results have big effects on the growth of infrastructure because they help engineers and managers make smart choices about how to lower risks, improve design, and make infrastructure in the Bhandara region last longer and be safer. In the larger field of geotechnical engineering and crisis preparation, this study adds to it by showing how important specific studies are for building strong infrastructure in areas that are prone to earthquakes.

Geological and hydrogeological drivers of seismic deformation in L’Aquila, Italy: insights from InSAR analysis

Historical and recent earthquakes have struck the city of L'Aquila, located in the axial zone of the Central Apennines, Italy, causing severe damage to the historic centre. Recent studies have shown that higher intensity of damage to buildings in L’Aquila downtown, both in the case of the 2009 earthquake (Mw: 6.29) and the 1703 earthquake (Mw: 6.7), is associated with higher post-seismic subsidence rates, detected through A-DInSAR maps, in the time range 2010–2021. This finding suggests the existence of geological factors that drive deformation (and building damage). The availability of long time series of InSAR data acquired from the Cosmo-SkyMed and Sentinel-1 missions, has enabled us to analyze the relationships between ground deformations and geological, hydrogeological, and geomorphological factors that may affect them. The correlation analysis between predisposing factors and SAR deformation has highlighted an increase in subsidence strongly conditioned by the outcropping lithology, showing how compositional variations within lithology can significantly influence ground deformations. Furthermore, hydrogeology has been recognized as playing an important role in determining deformation processes: the water table depth locally influences long-term subsidence, while seasonal fluctuations in the water table may be responsible for secondary areal variations in ground deformations.

Numerical simulation of stress evolution and seismic moment budget along the central segments of the Xianshuihe-Xiaojiang fault system: Implications for seismic hazard assessment

The central segments of the Xianshuihe-Xiaojiang fault system (CSXXFS), which intersect densely populated areas, have remained seismically quiet without any strong earthquakes of M ≥ 7 for nearly two centuries. As such, conducting a comprehensive seismic hazard assessment of the CSXXFS serves as a crucial component of disaster mitigation efforts. To achieve this, we developed a finite element model that integrates heterogeneous mechanical properties constrained by interseismic deformation to estimate the fault locking depths within the CSXXFS. Subsequently, we performed an analysis of the seismic moment budget and Coulomb stress change to comprehensively assess the seismic hazards in the vicinity of the CSXXFS. Our findings revealed an overall average locking depth of 10 km for the Xianshuihe-Xiaojiang fault system (XXFS) and 15 km for the Daliangshan fault (DLSF). The discrepancy between the seismogenic depth and the fault locking depth indicates the presence of deep creep in certain segments of the CSXXFS. Additionally, historical earthquakes have caused stress modulation, resulting in potential earthquakes being either delayed or advanced in different segments of the CSXXFS. Specifically, the future seismic hazard is delayed in the entire Zemuhe fault (ZMHF), the northern segment of the Anninghe fault (ANHF), the southern section of the Shimian-Yuexi segment of the north Daliangshan fault (NDLSF), and the southernmost part of the south Daliangshan fault (SDLSF). Conversely, the potential earthquake on the Mianning-Xichang segment of the ANHF and the majority of the DLSF have been advanced due to positive earthquake-induced stress. Our estimation of the seismic budget suggests that the ANHF, ZMHF, NDLSF, and SDLSF have the potential to host earthquakes with magnitudes of M 6.9, M 7.3, M 7.4, and M 7.1, respectively. By adopting this integrated seismic hazard analysis, we highlight the necessity of closely evaluating potential risks and implementing appropriate mitigation strategies in this area.

Seismotectonics-Driven Estimation of b-Value: Implications for Seismic Hazard Assessment

Abstract Taking full advantage of good-quality historical earthquake and seismogenic source data available for Italy (Catalogo Parametrico dei Terremoti Italiani [CPTI15] and Database of Individual Seismogenic Sources [DISS] databases), we tested the regional variability of the b-value of the Gutenberg–Richter law, focusing on the dominantly extensional, nearly 1200-km-long seismogenic corridor straddling the Apennines chain; an 18,200 km2 area generating about 45% of the seismic moment released countrywide. We carefully chose and tested the most appropriate completeness interval and completeness magnitude (Mc), and used the Lilliefors method, the Utsu test, and a bootstrap technique to verify the quality of our results and inferences. The 0.65 b-value we obtained is substantially lower than b-values used in Italian seismic hazard models, often close to 1.0; yet it predicts more accurately the observed Apennines earthquake record, suggesting that most currently adopted magnitude-frequency distributions underpredict events in the Mw range 6.0–7.1 and overpredict those in the range 5.2–5.5. We also highlight that the time, space, and magnitude distribution of the largest Italian earthquakes hardly follows the Gutenberg–Richter law: it rather favors a characteristic behavior. We contend that the b-value is too critical of a parameter for being calculated using statistically weak data sets, such as those resulting from overly detailed area-source models: one may end up characterizing low-hazard areas more accurately than high-hazard areas. Conversely, we advocate the use of fewer, larger area sources that fully exploit the current understanding of regional seismotectonics, as a way of obtaining more realistic regional hazard models.

Hybrid seismic vulnerability models for regional structures considering bivariate intensity measures

The multiple-probability decision-making method for earthquake hazards considers multiple performance indicators and can be used to effectively estimate the seismic risk of structures. The seismic vulnerability model directly affects the development of the earthquake risk distribution in regional structures. This paper innovatively developed a bivariate intensity measurement method based on macroscopic and instrumental seismic intensities. An optimized instrument intensity calculation model was established considering the actual monitoring data of historical earthquakes in China. A hybrid seismic vulnerability quantification method based on empirical, expert judgement and analysis has been proposed and applied to evaluate the vulnerability levels of three types of building clusters in two typical earthquakes in Qinghai Province, China (the 2008 Dachaidan (DCD) earthquake and the 2009 Haixi (HX) earthquake). A structural hybrid vulnerability matrix and surface for nine zones based on bivariate intensity measures were developed. A synthetic vulnerability membership index considering fuzzy failure criteria and decision theory was proposed, and vulnerability membership curves for different vulnerability levels were established. An improved earthquake economic loss prediction function is proposed, and synthetic economic vulnerability index prediction models for three typical buildings in different regions are established. The estimated and calculated results of the developed multiscale variable parameter synthetic vulnerability model are highly consistent with the actual earthquake loss observations.

Influence of Farallon Slab Loading on Intraplate Stress and Seismicity in Eastern North America in the Presence of Pre‐Existing Weak Zones

AbstractDespite the stability of the continental interior, eastern North America has hosted many significant historical earthquakes. Seismicity concentrates within tectonically inherited structures, which can act as weak zones where stress accumulates. Within these zones, systematic stress rotations may be explained by long‐wavelength sources. We test the hypothesis that mantle‐flow driven by the Farallon slab contributes to intraplate seismicity via the reactivation of pre‐existing faults. We model the stress field using seismically constrained global high‐resolution finite‐element flow models with CitcomS. To isolate the slab's effect, we vary its buoyancy between a case of neutrality and a case with full negative thermal buoyancy derived from tomography. Low‐viscosity lithospheric weak zones located at failed rifts, loaded by a mass anomaly at depth, transmit elevated stresses to the overlying crust. The sinking of the Farallon slab drives localized mantle flow beneath the central‐eastern US, generating a large stress amplification of 100–150 MPa peaking over the New Madrid Seismic Zone (NMSZ). This stress amplification exerts a continent‐wide clockwise rotation on the stress field, which in the presence of weak zones reproduces some observed deviations of the seismically inferred SHmax from the regional borehole SHmax, bringing optimally oriented faults, closer to failure, some of which are associated with major historical earthquakes, including the Reelfoot Fault in the NMSZ and the Timiskaming Fault in Western Quebec. However, stronger lithospheric viscosity gradients, shallower weak zones, or weaker faults are still needed to fully reproduce the observed stress field in some areas.

Holocene surface-rupturing paleo-earthquakes along the Kachchh Mainland Fault: shaping the seismic landscape of Kachchh, Western India

This study explores the seismotectonics of Kachchh in western India, a region with a low-to-moderate strain rate and a history of significant earthquakes, notably the 1819, Mw 7.8 Allah Bund, and the 2001, Mw 7.6 Bhuj. Despite its substantial seismic risk, comprehensive studies on Kachchh’s seismogenic sources are scarce. This is attributed to the concealed nature of active structures, hindering definitive age constraints in paleoseismological research. Our research comprises a detailed paleoseismic analysis of the north-verging, reverse Jhura Fault underlying the Jhura anticline, a segment of the Kachchh Mainland Fault. This fault segment shows evidence of surface-rupturing earthquakes in the area south of the Great Rann of Kachchh. The investigation reveals three paleoseismic events: Event I before 9.72 ka B.P., Event II between 8.63–8.20 ka B.P., and Event III between 6.20–6.09 ka B.P. The elapsed time since the last event on this fault is > 8000 years, suggesting that the area is exposed to a significant earthquake hazard. This highlights the need for more precise characterization of individual seismogenic sources for future earthquake preparedness.