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shear-wave velocity structure of the crust and uppermost mantle in the Shanxi rift zone

Earthquake Science 2015年第2期28卷 135-149页

作者： Meiqing Song Yong Zheng Chun Liu Li Li Xia Wang Earthquake Prediction Center Earthquake Administration of Shanxi Province Institute of Geodesy and Geophysics Chinese Academy of Sciences Earthquake Administration of Shaanxi Province Earthquake Administration of Shanxi Province

The Shanxi rift zone is one of the largest and active Cenozoic grabens in the world, studying the velocity structure of the crust and upper mantle in this region may help us to understand the mechanisms of rift processes and the seismogenic environment of active seismicity in continental rifts. In this work, using the broadband seismic data of Shanxi, Hebei, Henan, Shaanxi provinces, and the Inner Mongolia Autonomous Region from February 2009 to November 2011, we have picked out 350 high-quality phase velocity dispersion curves of fundamental mode Rayleigh waves at periods from 8 to 75 s, and Rayleigh wave phase velocity maps have been constructed from 8 to 75 s period with horizontal resolution ranging from 40 to 50 km by two-station surface-wave tomography. Then, using a genetic algorithm, a 3D shear-wave speed model of the crust and uppermost mantle have been derived from these maps with a spatial resolution of 0.4° × 0.4°. Four characteristics can be outlined from the results：（1） Except in the Datong volcanic zone, in the depth range of 11-30 km, the location of a transition zone between the highand low-velocity regions is in agreement with the seismicity pattern in the study region, and the earthquakes are mostly concentrated near this transition zone; （2） In the depth range of 31-40 km, shear-wave velocities are higher to the south of the Taiyuan Basin and lower to the north, which is similar to the distribution pattern of Moho depth variations in the Shanxi region; （3） The shear-wave velocity pattern of higher velocities to the south of 38×N and lower velocities to the north is found to be consistent with that from the upper crustal levels to depth of 70 km. At the deeper depths, the spatial scale of the low-velocity anomalies zone in the north is gradually shrinking with depth increasing, the low-velocity anomalies are gradually disappearing beneath the Datong volcanic zone at the depth of 151-200 km. We proposed that the root of the Datong volcano may reac

关键词： Shanxi rift zone Two-station methodSurface wave shear-wave velocity Tomography

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Middle and upper crust shear-wave velocity structure of the Chinese mainland

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Acta Seismologica Sinica(English Edition) 2007年第4期20卷 359-369页

作者：冯梅安美建 Institute of Geomechanics Chinese Academy of Geological Sciences

In order to give a more reliable shallow crust model for the Chinese mainland, the present study collected many short-period surface wave data which are better sensitive to shallow earth structures. Different from traditional two-step surface wave tomography, we developed a new linearized surface wave dispersion inversion method to directly get a 3D S-wave velocity model in the second step instead of inverting for 1D S-velocity profile cell by cell. We convert all the regionalized dispersions into linear constraints for a 3D S-velocity model. Checkerboard tests show that this method can give reasonable results. The distribution of the middle- and upper-crust shear-wave velocity of the Chinese mainland in our model is strongly heterogeneous and related to different geotectonic terrains. Low-velocity anomalies delineated very well most of the major sedimentary basins of China. And the variation of velocities at different depths gives an indication of basement depth of the basins. The western Tethyan tectonic domain （on the west of the 95°E longitude） is characterized by low velocity, while the eastern Tethyan domain does not show obvious low velocity. Since petroleum resources often distribute in sedimentary basins where low-velocity anomaly appears, the low velocity anomalies in the western Tethyan domain may indicate a better petroleum prospect than in its eastern counterpart. Besides, low velocity anomaly in the western Tethyan domain and around the Xing＇an orogenic belt may be partly caused by high crustal temperature. The weak low-velocity belt along -105°E longitude corresponds to the N-S strong seismic belt of central China.

关键词： surface-wave tomography shear-wave velocity sedimentary basins shallow crust China

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Inversion of shear wave interval velocity on prestack converted wave data

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Acta Seismologica Sinica(English Edition) 2007年第2期20卷 180-187页

作者：魏修成王建民陈天胜 Petroleum Exploration and Production Research Institute SINOPEC Geophysical Exploration Company Daqing Petroleum Administrative Bureau

Seismic velocity is important to migration of seismic data, interpretation of lithology and lithofacies as well as prediction of reservoir. The information of shear wave velocity is required to reduce the uncertainty for discriminating lithology, identifying fluid type in porous material and calculating gas saturation in reservoir prediction. Based on Zoeppritz equations, a numeral and scanning method was proposed in this paper. shear wave velocity can be calculated with prestack converted wave data. The effects were demonstrated by inversion of theoretical and real seismic data.

关键词： converted wave prestack inversion shear-wave velocity

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An improved method of evaluating liquefaction potential with the velocity of shear-waves

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Acta Seismologica Sinica(English Edition) 2000年第6期13卷 679-686,718页

作者：柯瀚陈云敏 Geotechnical Engineering Research Institute Zhejiang UniversityHangzhou 310027China

According to the results of cyclic triaxial tests, a linear correlation is presented between liquefaction resistance and elastic shear modulus, which shows the relation of Gmax (kPa) with (σd/2)1/2(kPa)1/2. When applied to soils from different sites, the correlation can be normalized in reference to its minimum void ratio (emin). Accordingly, an improved method is established to evaluate the liquefaction potential with shear-wave velocity. The critical shear-wave velocity of liquefaction is in linear relation with 1/4 power of depth and the maximum acceleration during earthquakes, which can be used to explain the phenomenon that the possibility of liquefaction decreases with the increment of the depth. Compared with previous methods this method turns out simple and effective, which is also verified by the results of cyclic triaxial tests.

关键词： liquefaction potential shear-wave velocity cyclic triaxial te?

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Three-Dimensional Modeling of Shallow shear-wave Velocities for Las Vegas, Nevada, Using Sediment Type

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Journal of China University of Geosciences 2009年第3期20卷 555-562页

作者： Barbara Luke Helena Murvosh Wanda Taylor Jeff Wagoner University of Nevada Las Vegas Las Vegas NV USA Stanley Consultants Inc. Las Vegas NV USA Lawrence Livermore National Laboratory Livermore CA USA

A three-dimensional model of near-surface shear-wave velocity in the deep alluvial basin underlying the metropolitan area of Las Vegas, Nevada （USA）, is being developed for earthquake site response projections. The velocity dataset, which includes 230 measurements, is interpolated across the model using depth-dependent correlations of velocity with sediment type. The sediment-type database contains more than 1 400 well and borehole logs. Sediment sequences reported in logs are assigned to one of four units. A characteristic shear-wave velocity profile is developed for each unit by analyzing closely spaced pairs of velocity profiles and well or borehole logs. The resulting velocity model exhibits reasonable values and patterns, although it does not explicitly honor the measured shear-wave velocity profiles. Site response investigations that applied a preliminary version of the velocity model support a two-zone ground-shaking hazard model for the valley. Areas in which clay predominates in the upper 30 m are predicted to have stronger ground motions than the rest of the basin.

关键词： shear-wave velocity earthquake site response site amplification microzonation sediment type.

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A deep-learning-based approach for seismic surface-wave dispersion inversion(SfNet)with application to the Chinese mainland

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Earthquake Science 2023年第2期36卷 147-168页

作者： Feiyi Wang Xiaodong Song Mengkui Li SinoProbe Laboratory School of Earth and Space SciencesPeking UniversityBeijing 100871China Center of Artificial Intelligence Geosciences Institute for Artificial IntelligencePeking UniversityBeijing 100871China School of Geodesy and Geomatics Wuhan UniversityWuhan 430079China

Surface-wave tomography is an important and widely used method for imaging the crust and upper mantle velocity structure of the *** this study,we proposed a deep learning(DL)method based on convolutional neural network(CNN),named SfNet,to derive the vS model from the Rayleigh wave phase and group velocity dispersion *** a network model usually requires large amount of training datasets,which is labor-intensive and expensive to *** we relied on synthetics generated automatically from various spline-based vS models instead of directly using the existing vS models of an area to build the training dataset,which enhances the generalization of the DL *** addition,we used a random sampling strategy of the dispersion periods in the training dataset,which alleviates the problem that the real data used must be sampled strictly according to the periods of training *** using synthetic data demonstrate that the proposed method is much faster,and the results for the vS model are more accurate and robust than those of conventional *** applied our method to a dataset for the Chinese mainland and obtained a new reference velocity model of the Chinese continent(ChinaVs-DL1.0),which has smaller dispersion misfits than those from the traditional *** high accuracy and efficiency of our DL approach makes it an important method for vS model inversions from large amounts of surface-wave dispersion data.

关键词： deep learning surface-wave inversion shear-wave velocity Chinese mainland

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Crustal and uppermost mantle structure of SE Tibetan plateau from Rayleigh-wave group-velocity measurements

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Earthquake Science 2014年第4期27卷 411-419页

作者： Yonghua Li Jiatie Pan Qingju Wu Zhifeng Ding Key Laboratory of Seismic Observation and Geophysical Imaging China Earthquake Administration Institute of Geophysics China Earthquake Administration

A shear-wave velocity model of the crust and uppermost mantle beneath the SE Tibetan plateau was derived by inverting Rayleigh-wave group-velocity mea- surements of periods between 10 and 70 s. Rayleigh-wave group-velocity dispersions along more than 3,000 inter- station paths were measured based on analysis of telese- ismic wavelbrm data recorded by temporary seismic stations. These observations were then utilized to construct 2D group-velocity maps in the period range of 10-70 s. Tile new group-velocity maps have an enhanced resolution compared with previous global and regional group-velocity models in this region because of the denser and more uniform data coverage. The lateral resolution across the region is about 0.5° for the periods used in this study. Local dispersion curves were then inverted for a 3D shear-wave velocity model of the region by applying a linear inversion scheme. Our 3D shear-wave model confirms the presence of low-velocity zones （LVZs） in the crust beneath the northern part of this region. Our irnaging shows that the upper-middle crustal LVZ beneath the Tengchong region is isolated from these LVZs beneath the eastern and northern part of this region. The upper-middle crustal LVZ may be regarded as evidence of a rnagma chamber in the crust beneath the Tengchong Volcanoes. Our model also reveals a slow lithospheric structure beneath Tengchong and a fast shield-like mantle beneath the stable Yangtze block.

关键词： SE Tibetan plateau shear-wave velocity Rayleigh-wave tomography Group velocity

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Love and Rayleigh wave Tomography of the Qinghai-Tibet Plateau and Surrounding Areas

Love and Rayleigh Wave Tomography of the Qinghai-Tibet Plate...

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中国科学院地质与地球物理研究所第十届(2010年度)学术年会

作者： JOS BADAL Physics of the Earth Sciences BUniversity of Zaragoza Pedro Cerbuna 1250009 Zaragoza Spain

Surface wave data were initially collected from events of magnitude Ms≥5.0 and shallow or moderate focal depth occurred between 1980 and 2002:713 of them generated Rayleigh waves and 660 Love waves,which were recorded by 13 broadband digital stations in Eurasia and *** to 1,525 source-station Rayleigh waveforms and 1,464 Love wave trains have been processed by frequency-time analysis to obtain group *** inverting the path-averaged group times by means of a damped least-squares approach,we have retrieved location-dependent group velocities on a 2°×2°-sized grid and constructed Rayleighand Love-wave group velocity maps at periods 10.4-105.0 *** and covariance matrices and the rms group velocity misfit have been computed in order to check the quality of the ***,depth-dependent SV-and SH-wave velocity models of the crust and upper mantle are obtained by inversion of local Rayleigh- and Love-wave group velocities using a differential damped least-squares *** results provide:(a) Rayleigh-and Love-wave group velocities at various periods;(b) SV-and SH-wave differential velocity maps at different depths;(c) sharp images of the subducted lithosphere by velocity cross sections along prefixed profiles;(d) regionalized dispersion curves and velocity-depth models related to the main geological *** lithospheric root presents a depth that can be substantiated at～40 km (Qiangtang Block) and exceptionally at～80 km in some places (Lhasa Block),and which exhibits laterally varying fast velocity very close to that of some shields that even reaches～4.8 km/s under the northern Lhasa Block and the Qiangtang ***-velocity anomalies of 7-10% or more beneath southern Tibet and the eastern edge of the Plateau support the idea of a mechanically weak middle-to-lower crust and the existence of crustal flow in Tibet.

关键词： Surface waves group velocity shear-wave velocity tomography Qinghai-Tibet Plateau

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Effects of topography on propagation of high-frequency Love waves

Effects of topography on propagation of high-frequency Love ...

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信号处理在地球物理——浙江省信号处理学会2018年学术年会

作者： Chaoqiang Xi Jianghai Xia The School of Earth Science Zhejiang University

Multi-channel Analysis of Love wave(MALW) is a newly developed method for near-surface structural detecting,with simpler dispersion characteristics than Rayleigh *** Rayleigh waves,Love waves are formed by the interference of multiple reflection and refraction of SH waves and independent of P *** theory,surface wave propagation is usually strongly influenced by free surface *** study the propagation characteristics of Love wave on complex topographic conditions for near-surface applications,we simulate Love waves by the finite-difference method with two kinds of topographic model:depressed topographic surface models and uplifted topographic surface *** changing the slope of the topography,we study the changes of the energy,and analyze the impact of the topography change on the phase velocity dispersion *** numerical simulation results indicate that,depressed and uplifted topographies have different influence on the propagation of *** the analysis of dispersion spectrums of depressed topography model,the phase velocity of Love waves will be slightly less than theoretical velocity,especially in the low frequency *** dispersion energy was generate in the dispersion of uplifted topography *** with previous Rayleigh wave studieswith the same topography,the phase velocity of dispersion spectrums of Love waves is more accurate.

关键词： Love waves shear-wave velocity topography

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