Climatic and anthropogenic changes are reshaping global water resources, with the North China Plain (NCP) experiencing significant surface subsidence due to severe groundwater overexploitation over the past half-century. In this study, we integrate data from Interferometric Synthetic Aperture Radar, Global Navigation Satellite System, and hydraulic head measurements observed in 2015-2019 to investigate aquifers' physical properties and corresponding changes in groundwater storage in NCP. Geodetic measurements indicate seasonal and long-term deformation patterns. The amplitude of seasonal variation of deformation is up to 25 mm with phase lag behind the seasonal variation of water head. The integration of geodetic and hydrological data indicates that local aquifer storativity and clay lens thickness are 0.67x10-3-14.38x10-3 $0.67\times {10}<^>{-3}-14.38\times {10}<^>{-3}$ and 0.15-1.98 $0.15-1.98$ m, respectively. The average long-term subsidence due to sustained water storage loss is about 29 mm/yr, with a peak rate of similar to 120 mm/yr. Even though all regions show a long-term ongoing subsidence, the subsidence trend has slowed in about half of the NCP, which can be attributed to the impact of the South-to-North Water Diversion (SNWD) Project, especially in areas near the SNWD aqueducts. Moreover, we find a disparity in subsidence rates between Hebei and Shandong Provinces, reflecting the impact of different groundwater exploitation management in mitigating the subsidence. This research underscores the effectiveness of combining geodetic and hydrological data for assessing groundwater circulation and optimizing groundwater management.

Tibet Plateau is bordered to the east by the Longmen Shan Fault, adjacent to Sichuan Basin of the stable Yangtze Block. Across the Longmen Shan Fault zone, the topographic differential extends to 5 km, with the deep lithosphere varying by nearly 20 km. In contrast to the large strike-slip faults found within the plateau, the Longmen Shan Fault is an oblique thrust fault that shapes the plateau's boundary, enveloped in a more intricate structural and dynamic environment.The role of the Longmen Shan Fault remains a pivotal point in the ongoing debate regarding the formation of the Tibet Plateau. We have developed a two-dimensional viscoelastic finite element model, encompassing the Longmen Shan Fault, the Tibet Plateau, and the Sichuan Basin on either side. The model simulates, over geological timescales, the thickening process of the Tibet Plateau and the activity of the Longmen Shan Fault under the influence of gravity and the pushing of the Indian plate. The results demonstrate the adjusting role of the Longmen Shan Thrust Fault in the deformation pattern at the eastern edge of the plateau, explaining the difference in the topographic and lithosphere thickness between the Tibet and Sichan Basin. The thrust Longmen Shan Fault not only contributes to cumulative crustal thickening but also plays a role in the thickening of the mid-lower crust and upper mantle viscoelastic media on the Tibet Plateau side.

We present the 2023 U.S. Geological Survey time -independent earthquake rupture forecast for the conterminous United States, which gives authoritative estimates of the magnitude, location, and time -averaged frequency of potentially damaging earthquakes throughout the region. In addition to updating virtually all model components, a major focus has been to provide a better representation of epistemic uncertainties. For example, we have improved the representation of multifault ruptures, both in terms of allowing more and less fault connectivity than in the previous models, and in sweeping over a broader range of viable models. An unprecedented level of diagnostic information has been provided for assessing the model, and the development was overseen by a 19 -member participatory review panel. Although we believe the new model embodies significant improvements and represents the best available science, we also discuss potential model limitations, including the applicability of logic tree branch weights with respect different types of hazard and risk metrics. Future improvements are also discussed, with deformation model enhancements being particularly worthy of pursuit, as well as better representation of sampling errors in the gridded seismicity components. We also plan to add time -dependent components, and assess implications with a wider range of hazard and risk metrics.

The US National Seismic Hazard Model (NSHM) was updated in 2023 for all 50 states using new science on seismicity, fault ruptures, ground motions, and probabilistic techniques to produce a standard of practice for public policy and other engineering applications (defined for return periods greater than ∼475 or less than ∼10,000 years). Changes in 2023 time-independent seismic hazard (both increases and decreases compared to previous NSHMs) are substantial because the new model considers more data and updated earthquake rupture forecasts and ground-motion components. In developing the 2023 model, we tried to apply best available or applicable science based on advice of co-authors, more than 50 reviewers, and hundreds of hazard scientists and end-users, who attended public workshops and provided technical inputs. The hazard assessment incorporates new catalogs, declustering algorithms, gridded seismicity models, magnitude-scaling equations, fault-based structural and deformation models, multi-fault earthquake rupture forecast models, semi-empirical and simulation-based ground-motion models, and site amplification models conditioned on shear-wave velocities of the upper 30 m of soil and deeper sedimentary basin structures. Seismic hazard calculations yield hazard curves at hundreds of thousands of sites, ground-motion maps, uniform-hazard response spectra, and disaggregations developed for pseudo-spectral accelerations at 21 oscillator periods and two peak parameters, Modified Mercalli Intensity, and 8 site classes required by building codes and other public policy applications. Tests show the new model is consistent with past ShakeMap intensity observations. Sensitivity and uncertainty assessments ensure resulting ground motions are compatible with known hazard information and highlight the range and causes of variability in ground motions. We produce several impact products including building seismic design criteria, intensity maps, planning scenarios, and engineering risk assessments showing the potential physical and social impacts. These applications provide a basis for assessing, planning, and mitigating the effects of future earthquakes.

On 6 February 2023, two large earthquakes (moment magnitude 7.8 and 7.6) shocked a vast area of southeastern Türkiye and northern Syria, leading to heavy casualties and economic loss. To investigate the rupture process over multiple fault segments, we performed a comprehensive analysis of local seismic and geodetic data and determined supershear ruptures on the initial branch and the Pazarcık and Erkenek segments and subshear ruptures on the Amanos segment of event 1. The bilateral rupture of event 2 also presents distinct sub- and supershear velocities. The dynamic stress of the branch fault rupture triggered the Pazarcık segment initial rupture at a point 9 kilometers west of the junction of these two faults, boosting the supershear rupture of the Pazarcık segment of the main fault. The geometry and prestress level of multiple segments controlled the rupture behaviors and influenced the ground shaking intensity.

基于2015—2019共4年的合成孔径雷达(SAR)卫星影像,提出一种广域合成孔径雷达干涉测量(In-SAR)时序分析技术,对华北平原的地表形变进行高精度连续监测.首先对SAR影像进行干涉处理,得到干涉图.在此基础上,使用经过并行化改进的永久散射体技术斯坦福改进(StaMPS)方法,提取干涉图中所有永久散射体(PS)像元,获取研究区域全分辨率的时序形变信息.之后,使用大气模型校正法与共景叠加法相结合的联合大气校正方法,估计并去除形变信息中的大气噪声.经过上述处理流程后,成功地获取华北平原地表大空间尺度、长时间跨度、全空间分辨率和高精度的形变信息,进而监测到平原内部由长期地下水开采导致的高达100 mm/a的大范围强烈沉降信号.相较于既有算法,并行化StaMPS方法通过在多个计算节点之间的实时分配,节约至少60％的计算时间,联合大气校正方法则可以去除约74.3％的大气噪声项,有效性显著高于两种校正方法的单独使用效果.广域InSAR时序分析技术可以有效地实现对大范围地表形变的高精度连续监测.

ABSTRACT We present the 2023 U.S. Geological Survey time-independent earthquake rupture forecast for the conterminous United States, which gives authoritative estimates of the magnitude, location, and time-averaged frequency of potentially damaging earthquakes throughout the region. In addition to updating virtually all model components, a major focus has been to provide a better representation of epistemic uncertainties. For example, we have improved the representation of multifault ruptures, both in terms of allowing more and less fault connectivity than in the previous models, and in sweeping over a broader range of viable models. An unprecedented level of diagnostic information has been provided for assessing the model, and the development was overseen by a 19-member participatory review panel. Although we believe the new model embodies significant improvements and represents the best available science, we also discuss potential model limitations, including the applicability of logic tree branch weights with respect different types of hazard and risk metrics. Future improvements are also discussed, with deformation model enhancements being particularly worthy of pursuit, as well as better representation of sampling errors in the gridded seismicity components. We also plan to add time-dependent components, and assess implications with a wider range of hazard and risk metrics.

Crustal deformation and seismicity in Europe are still poorly understood. Seismic activity is classically ascribed to crustal strain rates generated by edge‐driven tectonic forces. However, crustal deformation is not only due to tectonic loading, but can also be related to isostatic and mantellic processes that induce additional stress and strain on the crust by flexure. The influence that those processes have on seismic activity, as well their interaction, is still controversial. The main limitation to study it is because the deformation and its causal mechanisms are usually analyzed separately in small regions. We present here a 3D secular velocity field that covers Eurasia and its plate boundaries including 4,863 Global Navigation Satellite System stations obtained by combining 10 different datasets. We have developed a method based on spatial filtering to identify outliers and smooth the velocity field, and have computed both strain and uplift rate maps that are interpreted in the light of the different driving processes that contribute to the 3D deformation in Europe. The vertical and horizontal deformation features are compared with seismic rates obtained from the spatial and temporal distribution of the seismicity in Europe. Our results suggest that is not possible to explain the seismicity in Europe with edge‐driven horizontal tectonic forces only. In some areas markers of the crustal flexure such as the vertical velocity field and its derivative, resulting from buoyancy‐driven processes, may help to interpret earthquake distribution.

This report describes geodetic and geologic information used to constrain deformation models of the 2023 update to the National Seismic Hazard Model (NSHM), a set of deformation models to interpret these data, and their implications for earthquake rates in the western United States. Recent updates provide a much larger data set of Global Positioning System crustal velocities than used in the 2014 NSHM, as well as hundreds of new faults considered as active sources for the 2023 NSHM. These data are interpreted by four geodetic models of deformation that estimate fault slip rates and their uncertainties together with off-fault moment release rates. Key innovations in the 2023 NSHM relative to past practice include (1) the addition of two new (in addition to two existing) deformation models, (2) the revision and expansion of the geologic slip rate database, (3) accounting for fault creep through development of a creep-rate model that is employed by the four deformation models, and (4) accounting for time-dependent earthquake-cycle effects through development of viscoelastic models of the earthquake cycle along the San Andreas fault and the Cascadia subduction zone. The effort includes development of a geologic deformation model that complements the four geodetic models. The current deformation models provide a new assessment of outstanding discrepancies between geologic and geodetic slip rates, at the same time highlighting the need for both geologic and geodetic slip rates to robustly inform the earthquake rate model.

Groundwater overexploitation is a critical issue in the North China Plain (NCP), resulting in groundwater level decline and surface subsidence for the last half-century. This problem, however, has been greatly alleviated by the South-to-North Water Diversion (SNWD) Project since 2015. Monitoring of this process has been steadily improved in recent years using water level and geodetic observations. Here, we characterize the water storage change at the Huairou groundwater reserve site (HGRS) in Beijing due to the SNWD by combining Interferometric Synthetic Aperture Radar (InSAR) data of the Sentinel-1 satellites, continuous Global Positioning System (GPS) data, and well water level data observed during the same time. InSAR observations revealed subsidence up to ~400 mm in the Beijing plain but uplift at ~40 mm in the HGRS during 2015–2019, and more than 70% of the uplift occurred from October 2018 to January 2019. By integrating the most significant uplift deformation during October 2018 to January 2019 with water level observations at the same time, we estimated the storativity of the confined aquifer system at HGRS as 1.68–7.82×10−3, weighing in the correction for effective stress and surface deformation for various situations. Based on the estimated aquifer storativity and the observed water level change in the unconfined and confined aquifer, the recharged water storage for the confined and unconfined aquifers was estimated as 1.20–1.39×107 m3 and ~2.86×108 m3 from 6 October 2018 to 22 January 2019, respectively, which is about 4% and 91% of the surface water recharge through river channels in the same period due to the SNWD Project. Our study demonstrates that integration of geodetic and hydrological data can provide crucial information for the assessment of groundwater circulation and assistance of groundwater management.

SUMMARYThe 2021 Mw7.4 Maduo earthquake occurred on the Jiangcuo fault within the Bayan Har block in eastern Tibet. It is a rather unique event and attests that large earthquakes can occur in the interior of major tectonic blocks within the Tibetan plateau. By processing GPS data observed in the eastern Tibet region, we produce a data set documenting 3-D coseismic displacements of the Maduo earthquake. Using the data set to constrain a coseismic slip model, we find that the earthquake ruptured a nearly vertical fault about 170 km in length, with ∼90% of the moment released in the shallow layer above 20 km depth. The maximum slip of ∼3.6 m occurred near the surface around a bend in the east segment of the fault. The overall seismic moment release is 1.82 × 1020 N m and is equivalent to Mw7.4. Driven by the eastward extrusion of the Tibetan plateau, the deformation field in eastern Tibet is dominated by left-lateral shear, with the strikes of the tectonic faults rotating clockwise from west to east along with the shear stress orientation. This deformation pattern explains the mechanisms of earthquakes along block boundary faults, as well as the ones on faults within the blocks. The Jiangcuo fault is located ∼70 km south of the East Kunlun fault and could be connected to the Kunlun Mountain Pass fault to its WNW that ruptured during the 2001 Kokoxili earthquake, and a seismic gap of ∼240 km long between the two faults is worth special attention for its increased earthquake potential.

Postseismic processes provide important opportunities to probe into and investigate the frictional, viscous, and porous properties of the seismogenic fault and the surrounding Earth media. To accommodate the temporal and spatial resolutions and long‐term baseline stability of different deformation data, we develop a full time‐series inversion (FTI) technique, which jointly inverts for afterslip patterns using full time series of Global Navigation Satellite System, SAR, and strainmeter data. The FTI linearizes the inversion problem with a prescribed source evolution function to achieve efficient inversion. We conduct synthetic tests to validate the spatial and temporal resolution of the FTI algorithm. FTI outperforms static inversion techniques in terms of inversion stability under high noise level. We apply different parameterization strategies to evaluate its resolution for slip evolution parameters. The tests show that FTI can discriminate spatially separated afterslip with distinct evolution functions. Finally, we apply FTI to investigate the afterslip process following the 2017 M w 7.3 Sarpol‐e Zahab earthquake that occurred along the Iran‐Iraq border in northwestern Zagros using Synthetic Aperture Radar Interferometry time series derived from the Sentinel‐1 observations 1 year after the mainshock. Similar to the synthetic tests, the algorithm is capable to discriminate afterslip with different evolution functions in the up‐ and downdip portions of the coseismic rupture zone. By comparing with the stress‐driven afterslip model simulated using rate‐strengthening frictional law, we demonstrate the stability of FTI in resolving the afterslip process. We emphasize the importance of incorporating early postseismic observations for deciphering afterslip evolution and frictional parameters.

We develop a crustal deformation model of the western conterminous United States for the 2023 update of the National Seismic Hazard Model (NSHM). The kinematic finite-element code NeoKinema is used to describe crustal deformation, including long-term slip on faults and off-fault strains (both elastic and permanent). Three different data sets-Global Positioning System (GPS) velocities, geological fault offset rates, and crustal stress orientations-are used to constrain the model, and the plate tectonic rotation of Pacific relative to North America is also imposed on some boundaries. Compared to the last NSHM model update in 2014, the GPS and geological fault data are substantially updated, and new corrections are implemented in both the data and modeling approach, including the correction of the "ghost transient" effect due to postseismic deformation following large historic earthquakes, and correction for shallow creep on faults estimated from independent data. Based on these modeling results and a plate tectonic model of the Cascadia subduction zone, a long-term seismicity rate map is also computed for the western United States; this map is independent of the local seismic catalog and can, therefore, be tested retrospectively as well as prospectively. We find good success in most of the region, except in Cascadia, where the 45 yr instrumental seismicity record is much quieter than the forecast of our long-term model.

The deformation mode of the Tibetan Plateau is of crucial importance for understanding its construction and extrusion processes, as well as for the assessment of regional earthquake potential. Block motion and viscous flow models have been proposed to describe the deformation field but are not fully supported by modern geophysical observations. The 2021 Mw 7.4 Maduo earthquake, which occurred inside the Songpan-Ganzi terrane (SGT) in central-east Tibet, provides a chance to evaluate the associated deformation mode of the region. We conduct a joint inversion for this earthquake and resolve a bilateral rupture process, which is characterized by super- and subshear rupture velocities, respectively. We interpret this distinct rupture behavior to be the result of the respective slip concentration depths of the two ruptured segments. We analyze geological, seismic, and geodetic evidence and find that the SGT upper crust shows distributed shear deformation and distinct transverse anisotropy, which are associated with folded structures originating from compression of the paleo-Tethys ocean accretional prism realigned by following shear deformation. The SGT receives lateral shear loading from its NS boundary and accommodates a right-step sinistral motion across the terrane boundary faults. The unique tectonic setting of the SGT defines locations and behaviors of internal faulting and strong earthquakes such as the 2021 Maduo earthquake, with the latter occurring on slow-moving faults at intervals of several thousands of years.

Crustal deformation and seismicity in Europe are still poorly understood. Seismic activity is classically ascribed to crustal strain rates generated by tectonic deformation. However, crustal deformation is not only due to tectonic loading, but can also be related to isostatic and buoyancy processes that induce additional strains on the crust by flexure. The influence that those processes have on seismic activity, as well their interaction, is still controversial, and the main limitation to study it is because the deformation processes are commonly analyzed separately in small regions. We present here a 3D secular velocity field that covers Eurasia and its plate boundaries including 4508 GNSS stations obtained by combining 10 different datasets. We have developed a method based on spatial filtering to identify outliers and smooth the velocity field, and have computed a strain rate map representative of the main deformation processes that affect Europe. The vertical and horizontal deformation features were compared with earthquake recurrence models obtained from the spatial and temporal distribution of the seismicity in Europe. Our results suggest that is not possible to explain the seismicity of Europe based on the horizontal strain rate maps only. In some areas markers of the crustal flexure such as the vertical velocity field and its derivative, may help to interpret earthquake distribution models derived from geodetic data.

We establish a continuous GPS transect crossing the central Altyn Tagh fault at 90°E with eight years of observations. GPS velocities along this profile and another one crossing the fault at 86°E suggest a fault slip rate of 12.4 ± 0.7 mm/yr, but with asymmetric straining of adjacent terrain. On the south side, ∼8.2 mm/yr of left‐lateral shear is absorbed across a region ∼210 km from the fault, but only ∼4.2 mm/yr is found on the north side. This estimate of slip rate is ∼30% larger than the consensus estimate of previous models. By treating the deforming regions as elastic plates with different thicknesses overlying a substrata that obeys a linear Maxwell viscoelastic constitutive relationship, we infer a viscosity of ∼5.1 × 10 19 Pa s (between 3.5 and 9.1 × 10 19 Pa s at 1‐σ) on the south side, beneath northern Tibetan Plateau. This low viscosity, compared to some estimates for the asthenosphere, concurs with the Tibetan Plateau being underlain by a relatively hot and weak lower crust and upper mantle. The effective elastic thickness on the south side is 16.5–20 km, which is significantly smaller than that of the Tarim Basin of >60 km.

Tectonic research of the Tibetan Plateau has long focused on its deformation style and mechanisms. The 2008 Mw7.9 Wenchuan earthquake ruptured the Longmen Shan fault located at the eastern rim of the plateau and excited a viscoelastic response of the lithosphere. We infer a three‐dimensional (3D) rheological structure of eastern Tibet from modeling nine years of postseismic displacements observed by GPS. Our solution provides tight constraints on the lower‐crustal and upper‐mantle steady‐state viscosities of the Songpan‐Ganzi Terrane as (5.0 ± 0.7) × 1018 and (1.3 ± 0.3) × 1019 Pa s, respectively, consistent with a “jelly sandwich” model of Tibet, but not with some crustal channel flow models featuring much lower viscosities. The inferred lower‐crustal and upper‐mantle transient viscosities are (5.0 ± 1.3) × 1017 and (5.0 ± 1.5) × 1018 Pa s, respectively, suggesting nonlinear deformation mechanisms. The adjacent West Qinling and Sichuan blocks feature an order‐of‐magnitude higher rheological strength, which is consistent with the changes in the crustal material properties and interseismic deformation style across the East Kunlun‐Tazang and Longmen Shan faults. Our results enable us to propose a conceptual 3D tectonic deformation model, in which the eastward extrusion of Tibet is absorbed in the Songpan‐Ganzi crust mainly by E‐W shortening and N‐S extension, accommodated through faulting of conjugate strike‐slip faults in the upper crust and distributed shear in the lower crust.

Industrial production activities associated with salt mining, hydraulic fracturing, or geothermal exploitation can induce pore pressure and stress field changes, thus inducing seismic activity. Most of the events are not disastrous due to limited energy radiated. Here we report a Mw 5.8 damaging event that occurred in Changning, China on June 17, 2019, probably the largest induced event by industrial exploitation ever recorded. The earthquake is located within the Changning anticline, and it raises great concerns on why and how the event occurred in a relatively quiescent area in terms of tectonic activity. Moreover, it has been debated whether this earthquake ruptured solely on the fold-accommodation faults or also involved a deep-rooted fault under the anticline. By using InSAR data from two satellites, we investigate the detailed rupture and slip pattern of this earthquake. We propose a cascade rupture mode of the fold-accommodation faults, through poroelastic modeling of excess pore pressure by fluid injection and pumping operations and static Coulomb stress calculation on the pre-stressed faults. We argue that water injections may have triggered this event. The result highlights the importance of reassessing seismic hazard over similar tectonic environments with intensive industrial exploitation.

Despite the importance of viscoelasticity in the evolution of crustal stress/strain being widely recognized, the interpretation of interseismic geodetic measurements for assessing earthquake potential is still based overwhelmingly on elastic models. The reasons for this disparity include conflating deformation rates with deformation itself and the lack of a succinct representation of the seismic readiness of a locked fault in a viscoelastic Earth. Using a classical viscoelastic model for strike‐slip faults, we reiterate the commonly overlooked message that, if the recurrence interval is long, most of the strain energy for the next earthquake accrues early in the cycle, and low strain rates later in the cycle by no means indicate diminished rupture potential. Fault stress stays near failure for much of the late interseismic period which may explain why slow slip‐rate faults have more variable recurrence intervals than fast slip‐rate faults. We propose to use displacement deficit instead of slip deficit to represent seismic readiness.