Geophysical forward modeling serves as a fundamental theoretical approach for characterizing subsurface structures and material properties, essentially involving the computation of gravity responses at surface or spatial observation points based on a predefined density distribution. With the rapid development of data-driven techniques such as deep learning in geophysical inversion, forward algorithms are facing increasing demands in terms of computational scale, observable types, and efficiency. To address these challenges, this study develops an efficient forward modeling method based on voxel discretization, the enabling rapid calculation of gravity anomalies and radial gravity gradients on multiple observational surfaces. Leveraging the parallel computing capabilities of graphics processing units (GPU), together with tensor acceleration, Compute Unified Device Architecture (CUDA) execution, and Just-in-time (JIT) compilation strategies, the method achieves high efficiency and automation in the forward computation process. Numerical experiments conducted on several typical theoretical models demonstrate the convergence and stability of the calculated results, indicating that the proposed method significantly reduces computation time while maintaining accuracy, thus being well-suited for large-scale 3D modeling and fast batch simulation tasks. This research can efficiently generate forward datasets with multi-view and multi-metric characteristics, providing solid data support and a scalable computational platform for deep-learning-based geophysical inversion studies.

The deep learning-based gravity anomaly inversion method addresses the complex challenge of deriving subsurface density variation models from surface gravity anomaly data. In order to generate various geological environments and their corresponding surface gravity anomaly datasets, three-dimensional density models considering different spatial locations and density variations are created in this paper. At the same time, the residual module and spatial attention mechanism are introduced into the U-Net architecture to improve the learning ability and inversion accuracy of complex geological structures. Experimental results demonstrate that the proposed method achieves the high-precision reconstruction of density variation models in complex anomaly environments, with a model residual error lower than 3%. Additionally, the inversion results of the density change and the gravity change in the Longshoushan fault zone show that the 2022 Menyuan MS6.9 earthquake is in the middle of the positive and negative density changes, which verifies the applicability of the U-Net network in the field of gravity change data, highlighting the method’s value in the real-world environment.

The concentration of 56 volatile organic compounds (VOCs) in the ambient air of Shenyang was continuously monitored at four sites in 2021. The characteristics, sources, secondary pollution potential and health risks of VOCs in different functional regions of Shenyang were discussed. The results indicate that the concentration of VOCs in industrial regions was significantly higher than that in non-industrial regions, with a mean of 41.09 ± 69.82 parts per billion volumes (ppbv) compared to 19.99 ± 17.86 ppbv (commercial & residential region in urban fringe), 27.51 ± 28.81 ppbv (educational & scenic region) and 29.71 ± 23.97 ppbv (commercial & residential region in urban center). The positive matrix factorization (PMF) model was utilized to assign the sources of VOCs in Shenyang, and six factors were recognized: gasoline vehicles (34.8 %), diesel vehicles (28.3 %), combustion (11.4 %), biogenic emissions (9.7 %), industrial processes (8.2 %), and fuel evaporation (7.7 %). The results of the reactivity evaluation indicated that the ozone (O3) formation potential (OFP) was primarily influenced by industrial processes (29.2 %), diesel vehicles (25.7 %), biogenic emissions (17.0 %). These three factors were also the top three contributors to secondary organic aerosol formation potential (SOAP), accounting for 44.2 %, 9.4 % and 30.3 %, respectively. At the all four sites, the non-carcinogenic and carcinogenic risks of VOCs ranged from 1.6 × 10-2 to 3.8 × 10-2 and from 2.3 × 10-6 to 3.3 × 10-6, respectively. And the main risks can be attributed to emissions from industrial processes and gasoline vehicles. These findings suggested to strengthen the control of vehicle emissions throughout all regions in Shenyang and industrial processes emissions in industrial regions.

On September 5, 2022, Luding County in Sichuan Province, China experienced a Ms 6.8 earthquake. It is of significance to investigate the deep geodynamics and nucleation mechanism of the Luding earthquake for seismic hazard analysis and earthquake monitoring and forecasting in this region. In this study, we utilized EIGEN6C4 Bouguer gravity anomalies and SIO V15.1 topographic data to calculate the effective elastic thickness, Te, of the lithosphere in the southeastern margin of the Tibetan Plateau by finite difference method. The results indicate that the Luding earthquake occurred in a gradient zone with a steep change in Te between the eastern edge of the Tibetan Plateau and the Sichuan Basin, and that Te changes significantly, increasing from approximately 0-10 km in the west to about 10-30 km in the east. Based on the rheological structure information provided by Te , we constructed a two-dimensional numerical model to study the distribution of strain energy and displacement vector fields in the region. The results reveal that lower crustal flow is the key factor of the Luding earthquake nucleation. The lower crustal flow in the eastern edge of the Tibetan Plateau, impeded along the Shimian-Mianning-Xichang segment , migrates upward along the strong and weak lithospheric interface between the Sichuan-Yunnan rhumb block and the Gongga Mountain blocks, resulting in the gradual accumulation of stress and strain energy in the transitional zone between the upper and middle crust. This, in turn, triggers fluid migration upwards, facilitating the rupture of shallow rocks and the nucleation of the Luding earthquake. Drawing insights from Te and numerical simulation results, we proposes a plausible deep geodynamic model for the nucleation of the Luding earthquake and analyzes the seismic hazard of the Shimian-Mianning-Xichang segment along the Juanshui River-Anning River fault.

High-precision repeated absolute gravity observations conducted at the Luzhou observatory provide valuable insights into the processes of mass redistribution in the station's vicinity. In this study, we analyze four campaigns absolute measurements from two absolute gravimeters, FG5X-255 and FG5X-259, observed at the Luzhou gravity observatory and find a decrease in the gravity value of (− 93.3 ± 3.1) × 10 –8 m·s −2 from October 2020 to July 2022. By subtracting the contributions of vertical deformation, hydrological change, earthquake, and offset between instruments from the observation results, we derive a residual gravity change of (− 92.7 ± 4.1) × 10 –8 m·s −2 . Further analysis of field site photos and satellite images reveals that excavation related to the construction of a building near the Luzhou station is responsible for the observed gravity decrease. We use the load theory to calculate the gravity change at the Luzhou station due to the mass removal in the construction area and find that this factor could produce a gravity decrease consistent with the magnitude of the residual gravity change. Our results demonstrate that localized sources of mass redistribution, such as excavation at construction sites, can cause gravity variations exceeding 90 × 10 –8 m·s −2 nearby. Overall, our study highlights the importance of considering local mass redistribution when interpreting gravity variations.

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.

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.

We estimate the seismic hazard potential in the Sichuan-Yunnan region, western China using three different approaches. Our first approach, based on the assumption that the earthquake probability is proportional to the past seismicity rate, uses a regional earthquake catalog to constrain the probability model. A retrospective test shows that the 'forecasts' have some predictive power for strong events occurred on fault segments with shorter earthquake recurrence time, but not for that with longer recurrence time such as the Longmenshan fault. Our second approach, based on the assumption that the earthquake probability is proportional to crustal strain rate, uses secular geodetic strain rate deduced from GPS velocity data to constrain the probability model. A retrospective test of the model with earthquake occurrence of the past 30 years shows that the model 'forecasted' poorly. However, the model seems to 'forecast' spatial intensity of earthquakes for the past 500 years reasonably well, suggesting that the geodetic strain rate obtained at the decadal scale may still be a good indicator of long term earthquake activity in the region, but only at a time scale of hundreds of years. Our third approach uses GPS velocity data to determine the seismic moment accumulation rates on major faults, and a historical earthquake catalog to estimate seismic moments released in the past. Comparison of the two yields estimates of present day seismic moments cumulated on major faults, and a retrospective test shows some predictive power of the method. Our result suggests that numerous faults in the Sichuan-Yunnan region have cumulated seismic moments capable of producing M > 7.5 earthquakes, including the Xiaojiang, Jiali, Northern Nujiang, Nandinghe, and Red River-Puer faults, and the junction fault between the Xianshuihe and Ganzi-Yushu faults. (C) 2015 Elsevier Ltd. All rights reserved.

We present an algorithm to calculate horizontal strains (or strain rates) through interpolation of geodetically derived displacements (or velocities). This is an underdetermined inverse problem to derive smoothly distributed strains (or strain rates) using spatially discretized geodetic observations. A priori information, in the form of weighted smoothing, is critical to facilitate the solution. At a given site, the horizontal displacement (or velocity) field in its vicinity is approximated by a bilinear function and represented by rigid block translation, rotation, and strains (or their rates). The weighted displacement (or velocity) data in the neighborhood are used to estimate the field parameters through a least-squares inversion procedure. Optimal weightings are prescribed for the neighboring data, based on their distances to the interpolation site and their spatial coverage. Nonelastic strains resulted from surface fault rupture and creep may also be excluded from the solution. We apply this method to the Southern California Earthquake Center Crustal Motion Map version 4.0 velocity field and derive the strain-rate field in southern California. Our result shows that (1) distance-dependent weighting can be optimally achieved by employing either a Gaussian or quadratic decay function, with the former offering a slightly sharper result than the latter. (2) Spatially dependent weighting is important to improve the interpolation, and can be done by invoking either an azimuthal weighting or a Voronoi cell areal weighting function. (3) The strain-rate pattern in southern California is dominated by dextral shear of the San Andreas fault (SAF) system, and the secondary faults surrounding the Big Bend of the SAF strike at oblique angles with respect to the maximum shear direction, suggesting that tectonic deformation field on and off the SAF is dominated by mechanic processes of the SAF.

Research Article| January 01, 2014 Coulomb Stress Change and Evolution Induced by the 2008 Wenchuan Earthquake and its Delayed Triggering of the 2013 Mw 6.6 Lushan Earthquake Yanzhao Wang; Yanzhao Wang aState Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, Chinawangyz0513@gmail.commwang@gps.gov.cn Search for other works by this author on: GSW Google Scholar Fan Wang; Fan Wang bNational Geomatics Center of China, Beijing 100830, Chinawangfan0003@gmail.com Search for other works by this author on: GSW Google Scholar Min Wang; Min Wang aState Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, Chinawangyz0513@gmail.commwang@gps.gov.cn Search for other works by this author on: GSW Google Scholar Zheng‐Kang Shen; Zheng‐Kang Shen cDepartment of Earth and Space Sciences, University of California, Los Angeles, Los Angeles, California 90095‐1567 U.S.A.zshen@ucla.eduzhengkangshen@pku.edu.cn Search for other works by this author on: GSW Google Scholar Yongge Wan Yongge Wan dInstitute of Disaster Prevention Science and Technology, Yanjiao, Sanhe City, Hebei Province 065201, Chinawanyg217217@vip.sina.com Search for other works by this author on: GSW Google Scholar Author and Article Information Yanzhao Wang aState Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, Chinawangyz0513@gmail.commwang@gps.gov.cn Fan Wang bNational Geomatics Center of China, Beijing 100830, Chinawangfan0003@gmail.com Min Wang aState Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, Chinawangyz0513@gmail.commwang@gps.gov.cn Zheng‐Kang Shen cDepartment of Earth and Space Sciences, University of California, Los Angeles, Los Angeles, California 90095‐1567 U.S.A.zshen@ucla.eduzhengkangshen@pku.edu.cn Yongge Wan dInstitute of Disaster Prevention Science and Technology, Yanjiao, Sanhe City, Hebei Province 065201, Chinawanyg217217@vip.sina.com Publisher: Seismological Society of America First Online: 14 Jul 2017 Online ISSN: 1938-2057 Print ISSN: 0895-0695 © 2014 by the Seismological Society of America Seismological Research Letters (2014) 85 (1): 52–59. https://doi.org/10.1785/0220130111 Article history First Online: 14 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Yanzhao Wang, Fan Wang, Min Wang, Zheng‐Kang Shen, Yongge Wan; Coulomb Stress Change and Evolution Induced by the 2008 Wenchuan Earthquake and its Delayed Triggering of the 2013 Mw 6.6 Lushan Earthquake. Seismological Research Letters 2014;; 85 (1): 52–59. doi: https://doi.org/10.1785/0220130111 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search Almost five years after the 12 May 2008 Mw 7.9 Wenchuan earthquake, the Longmenshan fault zone was struck by the April 20 Mw 6.6 Lushan earthquake, with its hypocenter located ∼45 km southwest of the southern end of the Wenchuan surface rupture (Han et al., 2014; Zhang et al., 2014; Fig. 1). Such proximity in space and time between the two events implies that the later event is an aftershock of the previous one, or in other words, the previous event played a more important role in the occurrence of the latter... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

As the southeastern margin of the Tibetan plateau,the Sichuan-Yunnan region is carved by ample tectonic active faults. Many strong earthquakes have taken place in the past,and some of which resulted in massive damages and great losses of human lives. In this study we attempt to estimate the seismic hazard potential using two different approaches. Our first approach follows Kagan and Jackson(1994)and uses earthquake catalog data to estimate the mid-to long-term spatial probability of strong earthquakes,based on the assumption that earthquake likelihood is proportional to the intensity and quantity of past events. A retrospective test shows that the model offers reasonable ‘forecasts'statistically over the last 37 years,based on the catalog data of previous 470 years for model constraints. Our second approach is to use secular geodetic strain rate deduced from GPS velocity data to constrain earthquake probability model,assuming that likelihood of strong earthquakes is spatially proportional to the geodetic strain rate. A retrospective test of the model with earthquake occurrence of the past 30 years shows that the model ‘forecasted’poorly,but did reasonably well when comparing with the catalog data of the past 500 years,suggesting that the geodetic strain rate obtained at the decade scale may still be a good indicator of long-term earthquake activity in the region,but only at a time scale of hundreds of years.

The 14 April 2010 Mw 6.9 Yushu earthquake ruptured the northwestern segment of the Ganzi-Yushu fault in Qinghai Province, China. Using GPS data obtained from 1999 to 2007 in the vicinity of the Ganzi-Yushu fault, we estimate the slip rates of the Fenghuoshan and Ganzi-Yushu faults, and the northwestern segment of the Xianshuihe fault as 6.1±1.9, 6.6±1.5, and 9.7±0.7mm/a for left lateral components, and 2.8±1.9, 1.7±1.6, and −2.0±0.9mm/a for shortening components, respectively. The Maduo-Gande fault slips left laterally at a rate of about 1–2mm/a, and ~3mm/a sinistral shear motion is left unexplained, possibly caused by deformation across one or more unknown faults in the region. These results agree with geological estimates of the fault slip rates, and show a progressive increase of shear motion from northwest to southeast across segments of the Xianshuihe–Ganzi-Yushu fault zone, implying variation in transferring and absorbing deformation in different regions in and around the Tibetan plateau.

Two days after the March 11, 2011, M w 9.0 Tohoku-oki earthquake, Shinmoedake volcano, located on the Japanese island of Honshu, erupted. Was this eruption triggered by the Tohoku-oki earthquake? Could Mount Fuji and Changbaishan volcanoes also be triggered to erupt? By calculating changes in the regional stress-strain field that resulted from the earthquake, we find that Mount Fuji, Shinmoedake and Changbaishan volcanoes are all located in regions of volumetric expansion. The volumetric expansions at a depth of 10 km are up to ∼220 nano-strain, ∼8 nano-strain, and ∼14 nano-strain, respectively, for the three volcanoes. The strain changes inferred from GPS co-seismic displacements also suggest that these three volcanoes are located in regions with surface areal expansion. Considering that the expansional stress may cause the opening of magma channels, exsolution of CO2 gases stored in magma, and a series of positive feedback effects, the Tohoku-oki earthquake may result in an increase in the activity of these volcanoes. Attention should be paid to potential triggering of volcanic eruptions by stress changes induced by the Tohoku-oki earthquake.

Analysis of GEONET observations covering the entire territory of Japan shows that the great Tohoku-oki earthquake that occurred on March 11, 2011 off the east coast of Honshu in Japan caused an eastward movement of the northern part of the island by as much as 5.3 m. The GPS data from TEONET in China were used to derive far-field coseismic displacements and to assess the impact of the Tohoku-oki earthquake on crustal deformation in eastern China. The results reveal that the coseismic horizontal displacements induced by the earthquake are the level of millimeters to centimeters in North and Northeast China, with a maximum of 35 mm. Strain analysis also indicates that the earthquake resulted in an increase in the tensile strain on the north-northeast trending faults in North and Northeast China. The tensile strain imposed on the Yilan-Yitong and Dunhua-Mishan faults is more significant than that imposed on the faults in North China; the maximum normal strain reaches about 40 nano-strain. Considering that the static Coulomb stress loaded on the faults is limited, its effect on the regional seismic activity may not be significant.

2008年3月21日新疆于田发生Ms7.3级地震.本文通过处理、分析GPS数据,得到破裂断层北侧100 km附近的同震位移及震后形变信息.在观测区域GPS点监测到10 mm左右的同震位移,其中最大为南向14 mm,东向5 mm.同震位移呈现一致性的东南向运动特征,证实于田地震存在显著的左旋走滑分量.震后台站向西南方向运动,与同震位移方向不同,说明同震位移和震后形变具有不同的形变源.近普鲁断裂两侧的GPS点震后运动方向存在明显差异,表明于田地震可能触发了普鲁断裂的左旋滑动.普鲁断裂在于田地震发生后呈现的构造活动特征揭示普鲁断裂是康西瓦—西阿尔金断裂带的一部分,兼具左旋走滑与逆冲分量,吸收了青藏高原西北缘相对于塔里木盆地的东向逃逸与北向入侵作用.

The 14 April 2010 MW 6.9 Yushu earthquake ruptured the northwestern segment of the Ganzi-Yushu Fault in Qinghai,China.Accurate estimation of the secular slip rate across the fault would help understand tectonic structure of the fault and its seismogenic process.GPS data obtained from 1999 to 2007around the Ganzi-Yushu Fault spanning 89°～103°E,28°～39°N make such estimation possible.After removing GPS stations whose displacements were affected by fault locking effects and/or deformation of other faults,we decompose the remaining GPS station velocities into strike-parallel and strike-normal components and examine the data along profiles across corresponding fault segments.The slip rates of the Fenghuoshan,Ganzi-Yushu,and northwestern segment of the Xianshuihe Faults are estimated as 6.1±1.9,6.6±1.5,and 10.2±0.7mm/a,respectively.These results agree with geological estimates of the fault slip rates,which show progressive increase from northwest to southeast across segments of the Ganzi-Yushu-Xianshuihe Fault zone,implying variation in transferring and absorbing patterns of deformation in different regions in and around the Tibetan plateau.Estimation of present-day slip rates along segments of the Ganzi-Yushu Fault would provide valuable data for future research on seismo-tectonics of the fault and tectonic evolution of the Tibetan plateau.

据覆盖日本全境的GEONET网络GPS观测资料显示,2011年3月11日的日本宫城MW9.0级地震造成日本半岛向东移动,最大达到了5.3m.利用国家重大科技基础设施项目"中国大陆构造环境监测网络"的GPS观测资料,分析此次地震对中国大陆构造形变场的同震影响,结果显示,地震造成我国东北和华北地区产生毫米至厘米级的同震水平位移,最大值为35mm.通过应变分析发现,地震导致东北和华北地区一系列北北东走向的断裂产生了不同程度的张性应变.虽然在东北地区张性应变相对比较明显,最大处约为40nano-strain,但对断裂带的静态库仑应力加载有限,不会对区域地震活动产生大的影响.