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Geometry-preserving full-waveform tomography and its application in the longmen shan area

Science China Earth Sciences 2022年第3期65卷 437-448页

作者： Xingpeng DONG Dinghui YANG Hejun ZHU Yun CHEN Institute of Geology China Earthquake AdministrationBeijing 100029China Department of Mathematical Sciences Tsinghua UniversityBeijing 100084China Department of Geosciences The University of Texas at DallasDallas 75080USA State Key Laboratory ofLithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China

Classic L2-norm-based waveform tomography is often plagued by insurmountable cycle skipping problems;as a result,the iterative inversion falls into local minima,yielding erroneous images.According to the optimal transportation theory,we adopt a novel geometry-preserving misfit function based on the quadratic Wasserstein metric(W2-norm),which improves the stability and convexity of the inverse problem.Numerical experiments illustrate that W2-norm-based full-waveform tomography has a larger convergence radius and a faster convergence rate than the L2-norm and can effectively mitigate cycle skipping issues.We apply this method to the longmen shan area and obtain a reliable lithospheric velocity model.Our tomographic results indicate that the crystalline crust underlying the Sichuan Basin wedges into the crustal interior of the Tibetan Plateau,and the mid-lower crust of the eastern Tibetan Plateau is characterized by low shear-wave velocities,indicating that ductile crustal flow and strong interactions between terranes jointly dominate the uplift behavior of the longmen shan.Furthermore,we find that large earthquakes(e.g.,the Wenchuan and Lushan events)occur not only at the junction between high-and low-velocity regions but also in the transition zone from positive to negative radial anisotropy.These findings improve our understanding of the mechanism responsible for large earthquakes in this region.

关键词： Optimal transportation Geometry-preserving properties Cycle skipping problem longmen shan Lower crustal flow model

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Interpreting the Coseismic Uplift and Subsidence of the longmen shan Foreland Basin System during the Wenchuan Earthquake by a Elastic Flexural Model

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Acta Geologica Sinica(English Edition) 2016年第2期90卷 555-566页

作者： YAN Zhaokun LI Yong SHAO Chongjian ZHOU Rongjun YAN Liang ZHAO Guohua YAN Binglei State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation (CDUT) Chengdu 610059 China Sichuan Earthquake Administration Chengdu 610041 China

The coseismic surface uplift of the longmen shan（LMS） created an instantaneous topographic load over the western margin of the Sichuan Basin, where surface subsidence, decreasing eastward, has been measured using several methods, such as GPS, SAR and levelling. Using an elastic flexural model, we aim to interpret the coseismic surface uplift and subsidence, and constrain the effective lithospheric elastic thickness（Te） of the Sichuan Basin. Using different effective elastic thickness values for the Sichuan Basin, a series of subsidence curves were computed by the elastic flexure model equation for a broken elastic plate. The curves, produced by models using an effective elastic thickness of 30–40 km, provided the best fit to the general pattern of observed coseismic subsidence of the Sichuan Basin. However, the calculated subsidence（-40–70 cm） at the front of the LMS is evidently lower than the observed values（-100 cm）, suggesting that the effective elastic thickness therein should be lower. These results indicate that the lithospheric strength may decrease westward from the Sichuan Basin to the LMS.

关键词： flexural model longmen shan Wenchuan Earthquake coseismic uplift and subsidence foreland basin system

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Active Tectonics of the longmen shan Region on the Eastern Margin of the Tibetan Plateau

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Acta Geologica Sinica(English Edition) 2007年第4期81卷 593-604页

作者： ZHOU Rongjun LI Yong Alexander L.DENSMORE Michael A. ELLIS HE Yulin LI Yongzhao LI Xiaogang Institute of Earthquake Engineering Seismological Bureau of Sichuan Province Chengdu 610041 China National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Chengdu University of Technology Chengdu 610059 China Institute of Geology Department of Earth Sciences ETH Zentrum CH-8092 Ziirich Switzerland Center for Earthquake Research and Information University of Memphis 3890 Central Avenue Memphis TN 38152 USA

There is a massive amount of geomorphic evidence for active tectonics in the longmen shan at the eastern margin of the Tibetan plateau. We have surveyed some typical geomorphic markers including the Wenchuan-Maowen, Beichuan-Yingxiu and Pengxian-Guanxian faults, terrace offsets, scarps, fault-controlled saddles, dextral shutter ridges, dextral channel offsets, graben, shatter belts, and pull-apart basins. Electron spin resonance （ESR） and thermoluminescence（TL） ages were obtained using silty sand taken from below the surface of the sediments. According to these data, we calculated the rates of thrusting and strike-slip, and the results indicate that Cenozoic tectonic shortening at the plateau margin is minor with the rate of thrusting less than 1.10 mm/a and the rate of strike-slipping less than 1.46 mm/a. The longmen shan is a zone of NNE-trending dextral shear with slip-dip ratio of 6：1-1.3：1. From NW to SE, the thrust component becomes smaller, whereas the strike-slip component becomes larger.

关键词： tectonics strike-slip thrusting Late Cenozoic longmen shan Tibetan plateau

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Surface deformation related to the 2008 Wenchuan earthquake,and mountain building of the longmen shan,eastern Tibetan Plateau

Surface deformation related to the 2008 Wenchuan earthquake,...

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中国科学院地质与地球物理研究所第11届（2011年度）...

作者： Satoshi Okuyama Yoshiki Ninomiya Sarah Wright Geological Survey of Japan AISTTsukuba 305-8567Japan School of Earth Sciences University of MelbourneVictoria 3010Australia

The 12 May 2008 M 8.0 Wenchuan earthquake,China,was one of largest continental thrusting events worldwide.Based on interpretations of post-earthquake high-resolution remote sensing images and field surveys,we investigated the geometry,geomorphology,and kinematics of co-seismic surface ruptures,as well as seismic and geologic hazards along the longmen shan fold-and-thrust belt.Our results indicate that the Wenchuan earthquake occurred along the NE-SW-trending Yingxiu-Beichuan and Guanxian-Anxian faults in the longmen shan fold-and-thrust belt.The main surface rupture zones along the Yingxiu-Beichuan and Guanxian-Anxian fault zones are approximately 235 and 72 km in length,respectively. These sub-parallel ruptures may merge at depth.The Yingxiu-Donghekou surface rupture zone can be divided into four segments separated by discontinuities that appear as step-overs or bends in map view.Surface deformation is characterized by oblique reverse faulting with a maximum vertical displacement of approximately 10 m in areas around Beichuan County.Earthquake-related disasters(e.g., landslides) are linearly distributed along the surface rupture zones and associated river valleys. The Wenchuan earthquake provides new insights into the nature of mountain building within the longmen shan,eastern Tibetan Plateau.The total crustal shortening accommodated by this great earthquake was as much as 8.5 m,with a maximum vertical uplift of approximately 10 m.The present results suggest that ongoing mountain building of the longmen shan is driven mainly by crustal shortening and uplift related to repeated large seismic events such as the 2008 Wenchuan earthquake.Furthermore, rapid erosion within the longmen shan fold-and-thrust belt occurs along deep valleys and rupture zones following the occurrence of large-scale landslides triggered by earthquakes.Consequently,we suggest that crustal shortening related to repeated great seismic events,together with isostatic rebound induced by rapid erosion-related unloading,is a key component of the geo

关键词： MS 8.0 Wenchuan earthquake Co-seismic oblique reverse faulting Crustal shortening Mountain building longmen shan Eastern Tibetan Plateau

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Tectono–sedimentary Evolution of the Late Triassic Xujiahe Formation in the Sichuan Basin

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Acta Geologica Sinica(English Edition) 2013年第6期87卷 1554-1568页

作者： LUO Liang JIA Dong QI Jiafu WEI Guoqi DENG Fei State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum College of Geosciences China University of Petroleum School of Earth Sciences And Engineering Nanjing University Research Institute of Petroleum Exploration and Development PetroChina Company Limited Foshan Geological Survey

The early stage of Sichuan Basin formation was controlled by the convergence of three major Chinese continental blocks during the Indosinian orogeny that include South China,North China,and Qiangtang blocks.Although the Late Triassic Xujiahe Formation is assumed to represent the commencement of continental deposition in the Sichuan Basin,little research is available on the details of this particular stratum.Sequence stratigraphic analysis reveals that the Xujiahe Formation comprises four third-order depositional sequences.Moreover,two tectono-sedimentary evolution stages,deposition and denudation,have been identified.Typical wedge-shaped geometry revealed in a cross section of the southern Sichuan Basin normal to the longmen shan fold-thrust belt is displayed for the entire Xujiahe Formation.The depositional extent did not cover the Luzhou paleohigh during the LST1 to LST2 （LST,TST and HST mean Iowstand,transgressive and highstand systems tracts,1,2,3 and 4 represent depositional sequence 1,2,3 and 4）,deltaic and fluvial systems fed sediments from the longmen shan belt,Luzhou paleohigh,Hannan dome,and Daba shan paleohigh into a foreland basin with a centrally located lake.The forebulge of the western Sichuan foreland basin was located southeast of the Luzhou paleohigh after LST2.According to the principle of nonmarine sequence stratigraphy and the lithology of the Xujiahe Formation,four thrusting events in the longmen shan fold-thrust belt were distinguished,corresponding to the basal boundaries of sequences 1,2,3,and 4.The northern Sichuan Basin was tilted after the deposition of sequence 3,inducing intensive erosion of sequences 3 and 4,and formation of wedge-shaped deposition geometry in sequence 4 from south to north.The tilting probably resulted from small-scale subduction and exhumation of the western South China block during the South and North China block collision.

关键词： Xujiahe Formation tectono-sedimentary denudation longmen shan Sichuan Basin

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Stick-slip nucleation triggering of Wenchuan earthquake

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Geodesy and Geodynamics 2021年第1期12卷 11-20页

作者： Shuangxi Zhang Lingxi Liu Menkui Li Yu Zhang Jie Tang Xuchong Yi Department of Geophysics School of Geodesy and GeomaticsWuhan UniversityWuhan430079China Key Laboratory of Geospace Environment and Geodesy of the Ministry of Education Wuhan University430079WuhanChina

The MS8.0 Wenchuan earthquake occurred on May 12 th,2008 on the steeply reverse fault of the longmen shan fault zone,Western China.Catastrophic failure and rupture occurred along the listric sliding surface.Several numerical simulations have been performed to reconfigure the dynamic processes of this strong earthquake.However,few scientific studies on the stick-slip of the listric fault have been conducted.In this study,finite element method is utilized to simulate the instant stick-slip fault responses at the triggering moment.The fault surface is a non-continuous and frictional contact interface.The simulation results demonstrated that the sliding friction and sticking friction interact spatially.This interaction occurred temporarily on swarms of slip patches,rather than the entire fault slipping surface.Stick-slip causes serrated energy release,and transient aseismic slip can occur spontaneously.These tremors propagate from the epicenter upwards to the ground surface.Therefore,they may provide important details on earthquake onset rupture.

关键词： Stick-slip Tremor Wenchuan earthquake longmen shan Earthquake triggering Friction Numerical simulation

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Late Cenozoic denudation by large-magnitude landslides in the eastern edge of Tibetan Plateau

Late Cenozoic denudation by large-magnitude landslides in th...

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中国科学院地质与地球物理研究所2006学术年会

作者： Erchie Wang Institute of Geology and Geophysics Chinese Academy of SciencesBeituchengxilu 19Chaoyang District

Eastern edge of the Tibetan Plateau is marked by the longmen shan,which experienced pronounced denudation in late Cenozoic and was previously attributed to river erosion.Our recent work,however,demonstrated that the landsliding must have played an important integral role in the surface processes.Various-scale landslides are present in the peripheral zone of the southern longmen shan,which were interpreted as overthrust-related klippen in previous works.We revisited these exotic blocks,and demonstrated that they were actually gravity-driven landslides in origin.The landslides are composed mostly of thick-bedded marine limestone and sandstone of Paleozoic-Early Triassic ages,and were detached along some weak zones like Lower Silurian phyllite and unconformities.Three types of landslides can be categorized,distributed,stacked,and coherent,and their differential occurrence is considered to bear upon both uplift rates of the longmen shan and foreland topography.Outward flow of lowercrustal materials from the Tibetan Plateau interior provides a feasible mechanism for initiating the uplift of its eastern flank in Cenozoic.Positive feedbacks are believed to have existed between extrusion of lower-crustal channel flow and surface denudation processes.Rapid denudation by large-magnitude landslides in conjunction with coeval river erosion in the southern longmen shan might have led to predominant sub-vertical extrusion of lower-crustal flow channel,as evidenced by nearly symmetric exhumation of the Pengguan massif.The northern longmen shan was comparatively less denuded,with few basement rocks cropping out,and landslides are absent in its front as well.Differential denudation between the southern and northern longmen shan might have in large part resulted from the lower-crustal flow that presumably moved to the southeast and had less impact on the northern longmen shan.

关键词： Tibetan Plateau longmen shan Cenozoic denudation landslide

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Cosmogenic nuclide burial ages and provenance of Late Cenozoic deposits in the Sichuan Basin:Implications for Early Quaternary glaciations in east Tibet

Cosmogenic nuclide burial ages and provenance of Late Cenozo...

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中国科学院地质与地球物理研究所第11届（2011年度）...

作者： Ping Kong~(a,*),Yong Zheng~a,Bihong Fu~a a Key Laboratory of the Earth’s Deep Interior,Institute of Geology and Geophysics,Chinese Academy of Sciences,P.O.Box 9825,Beijing 100029,China

Collision between the Indian and the Eurasian plates since the early Cenozoic produces one of the world’s most remarkable continental escarpments between the Tibetan Plateau and the adjacent Sichuan Basin. Yet Tertiary sediments are rare in the Sichuan Basin;the oldest preserved Late Cenozoic deposits called Dayi conglomerates directly overlie the Cretaceous or Jurassic red beds.Using cosmogenic Be and Al burial dating,we obtain deposition ages of～2.0 Ma and catchment erosion rates of～400 mm/ka for the Dayi conglomerates.Zircon U-Pb age distributions suggest derivation of these conglomerates from the Songpan-Ganzi flysch,the Pengguan complex and Late Permian and Triassic granite plutons in the headwater regions of the Min Jiang(Jiang,a Chinese term,means river).The formation of the poorly-sorted, sub-angular to sub-rounded and tens-centimeter-sized deposits in the western margin of the Sichuan Basin,after long distance transportation,is best explained by glacial activity～2.0 Ma ago in east Tibet.

关键词： Dayi conglomerate longmen shan Cosmogenic nuclide Zircon U-Pb age Min Jiang Glaciations

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