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ambient noise Tomography, Green’s Function and Earthquakes

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International Journal of Geosciences 2022年第12期13卷 1082-1088页

作者： Panayiotis K. Varotsos Efthimios S. Skordas Department of Geology and Geoenvironment National and Kapodistrian University of Athens Athens Greece Department of Physics Section of Condensed Matter Physics and Solid Earth Physics Institute National and Kapodistrian University of Athens Athens Greece

Green’s function is well-known, among others, in the application of ambient noise tomography methodologies that may demonstrate the potential of hydrocarbon entrapment in the study area. Here it is also shown to be of key importance in identifying the fractal dimension in the unified scaling law for earthquakes as well as in studying an explicit relationship of a future strong earthquake epicenter to the average earthquake potential score. Such studies are now in progress.

关键词： Surface Wave Tomography Shear Velocity Model Inversion Green’s Function ambient noise Earthquakes

ambient noise H/V spectral ratio in site effects estimation in Fateh jang area, Pakistan

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Earthquake Science 2015年第1期28卷 87-95页

作者： S.M.Talha Qadri Bushra Nawaz S.H.Sajjad Riaz Ahmad Sheikh Department of Earth Sciences University of Sargodha College of Earth and Environmental Sciences University of the Punjab

Local geology or local site effect is a crucial component while conducting seismic risk assessment studies. Investigations made by utilization of ambient noise are an effective tool for local site estimation. The present study is conducted to perform site response analysis at 13 different sites within urban settlements of Fateh jang area （Pakistan）. The aim of this study was achieved by utilizing Nakamura method or H/V spectral ratio method. Some important local site parameters, e.g., the fundamental fre- quencies f0 of soft sediments, amplitudes A0 of corre- sponding H/V spectral ratios, and alluvium thicknesses over 13 sites within the study area, were measured and analyzed. The results show that the study area reflects low fundamental frequency fo. The fundamental frequencies of the sediments are highly variable and lie in a range of 0.6-13.0 Hz. Similarly, amplification factors at these sites are in the range of 2.0-4.0.

关键词： Local site effectspectral ratios Fundamentalfactor Alluvium thickness ambient noise H/Vfrequency Amplification

ambient noise as the new source for urban engineering seismology and earthquake engineering: a case study from Beijing metropolitan area

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Earthquake Science 2014年第1期27卷 89-100页

作者： Lanbo Liu Qi-fu Chen Weijun Wang Eric Rohrbach Department of Civil & Environmental Engineering University of Connecticut Institute of Earthquake Science China Earthquake Administration Institute of Geology and Geophysics Chinese Academy of Sciences

In highly populated urban centers, traditional seismic survey sources can no longer be properly applied due to restrictions in modern civilian life styles. The ambient vibration noise, including both microseisms and microtremor, though are generally weak but available anywhere and anytime, can be an ideal supplementary source for conducting seismic surveys for engineering seismology and earthquake engineering. This is funda- mentally supported by advanced digital signal processing techniques for effectively extracting the useful information out from the noise. Thus, it can be essentially regarded as a passive seismic method. In this paper we first make a brief survey of the ambient vibration noise, followed by a quick summary of digital signal processing for passive seismic surveys. Then the applications of ambient noise in engi- neering seismology and earthquake engineering for urban settings are illustrated with examples from Beijing metro- politan area. For engineering seismology the example is the assessment of site effect in a large area via microtremor observations. For earthquake engineering the example is for structural characterization of a typical reinforced con- crete high-rise building using background vibration noise.By showing these examples we argue that the ambient noise can be treated as a new source that is economical, practical, and particularly valuable to engineering seis- mology and earthquake engineering projects for seismic hazard mitigation in urban areas.

关键词： ambient noise Resonance frequency -Ground motion amplification Seismic vulnerability ~Horizontal to vertical spectra/ratio （HVSR） ~Seismic interferometry （SI） ~ Beijing metropolitan area

Three-Dimensional S-Wave Velocity Structure in Eastern Tibet from ambient noise Rayleigh and Love Wave Tomography

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Journal of Earth Science 2011年第2期22卷 195-204页

作者：徐小明李红谊宫猛丁志峰 Institute of Geophysics China Earthquake Administration School of Geophysics and Information Technology China University of Geosciences

We apply ambient noise tomography to continuous three-component broadband seismic data between January 1,2008 and December 31,2008 from the regional networks of 76 stations de-ployed by China Earthquake Administration.ambient noise cross-correlations were performed to produce the Green＇s functions of each station-pair.Within the period from 6 to 50 s,Rayleigh and Love wave dispersion curves were measured using the multiple filter analysis method.Then three-dimensional（3-D） S-wave velocity structures from the surface down to 70 km are inverted from both Rayleigh and Love wave dispersion results.The obtained S-wave velocity maps show strong lateral variations and correlate well with the distinct geological and tectonic features in the study area.The Sichuan basin displays low velocity in shallow depth due to thick sedimentary deposits but high velocity in the mid-lower crust;the eastern Tibetan plateau is clearly featured with a low-velocity zone in its mid-to-lower crust which is consistent with the crustal flow model proposed to explain the mechanism of uplift and pattern of deformation for the Tibetan plateau.Meanwhile,our results also exhibit that the crustal thickness decreased from the eastern Tibetan plateau to the Sichuan basin.

关键词： eastern Tibet ambient noise Green＇s function crustal and uppermost mantle structure.

Lithospheric structure and deformation in SE Tibet revealed by ambient noise and earthquake surface wave tomography: Recent advances and perspectives

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Earthquake Science 2012年第5期25卷 371-383页

作者： Huajian Yao Laboratory of Seismology and Physics of Earth's Interior School of Earth and Space SciencesUniversity of Science and Technology of China

High-resolution lithospheric structure is essential for understanding the tectonic evolution and deformation patterns of the southeastern Tibetan plateau. This is now possible due to recent advances in ambient noise and earthquake surface wave tomography, and great improvements in data coverage from dense portable array stations deployed in SE Tibet. In this review paper, I first give a brief overview of the tomographic methods from ambient noise and earthquake surface waves, and then summarize the major findings about the lithospheric structure and deformation in SE Tibet revealed by ambient noise and earthquake surface wave tomography as well as by other seismic and geophysical observations. These findings mainly include the 3-D distribution of mechanically weak zones in the mid-lower crust, lateral and vertical variations in radial and azimuthal anisotropy, possible interplay of some fault zones with crustal weak zones, and importance of strike-slip faulting on upper crustal deformation. These results suggest that integration of block extrusion in the more rigid upper-middle crust and channel flow in the more ductile mid-lower crust will be more compatible with the current geophysical observations. Finally I discuss some future perspective researches in SE Tibet, including array-based tomography, joint inversion using multiple seismic data, and integration of geodynamic modeling and seismic observations.

关键词： SE Tibet lithospheric structure deformation ambient noise earthquake surface waves

A pilot project of ambient noise tomography on a dense seismic array in Ji'nan urban area

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Earthquake Science 2018年第5期31卷 262-271页

作者： Feng Liang Lei Gao Zhihui Wang Tao Wang Kai Liu Sinoprobe Center-China Deep Exploration Center Chinese Academy of Geological Sciences

In this study, we conducted ambient noise tomography(ANT), with 33-day data, to investigate the nearsurface shear-velocity structure in downtown Ji’nan, Shandong Province, China. The cross-correlation functions with quiet clear Rayleigh waves are obtained with more symmetrical energy distribution which indicates that strong human activities, such as moving vehicles and municipal engineering construction, can produce approximately isotropic distribution of noise sources for high-frequency signals. The direct surfacewave tomographic method with period-dependent ray-tracing is used to invert all surface-wave dispersion data in the period band 0.2–1.5 s simultaneously for 3D variations of shear-velocity structure. The study result can help us better understand the local geologic structures, evaluate the distribution and geometry of the fracture-karst media, and assess hazards of the concealed active fault and its effect on the springs in the future.

关键词： ambient noise shear wave velocity urban geophysics urban underground space dense array

Love wave tomography in Italy from seismic ambient noise

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Earthquake Science 2010年第5期23卷 487-495页

作者： Hongyi Li Fabrizio Bernardi Alberto Michelini Key Laboratory of Geo-detection (China University ofGeosciences Beijing) Ministry of Education Beijing 100083 China School of Geophysics andlnformation Technology China University of Geosciences Beijing 100083 China Istituto Nazionale di Geofisica e Vulcanologia Via di Vigna Murata 605 Rome 00143 Italy

We estimate Love wave empirical Green＇s functions from cross-correlations of ambient seismic noise to study the crust and uppermost mantle structure in Italy. Transverse-component ambient noise data from October 2005 through March 2007 recorded at 114 seismic stations from the Istituto Nazionale di Geofisica e Vulcanologia （INGV） national broadband network, the Mediterranean Very Broadband Seismographic Network （MedNet） and the Austrian Central Institute for Meteorology and Geodynamics （ZAMG） yield more than 2 000 Love wave group velocity measurements using the multiple-filter analysis technique. In the short period band （5-20 s）, the cross-correlations show clearly one-sided asymmetric feature due to non-tmiform noise distribution and high local activities, and in the long period band （〉20 s） this feature becomes weak owing to more diffusive noise distribution. Based on these measurements, Love wave group velocity dispersion maps in the 8-34 s period band are constructed, then the SH wave velocity structures from the Love wave dispersions are inverted. The final results obtained from Love wave data are overall in good agreement with those from Rayleigh waves. Both Love and Rayleigh wave inversions all reveal that the Po plain basin is resolved with low velocity at shallow depth, and the Tyrrhenian sea is characterized with higher velocity below 8 km due to its thin oceanic crust.

关键词： ambient noise Love wave tomography crustal structure Italy

Three dimensional shear wave velocity structure of the crust and upper mantle beneath China from ambient noise surface wave tomography

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Earthquake Science 2010年第5期23卷 449-463页

作者： Xinlei Sun Xiaodong Song Sihua Zheng Yingjie Yang Michael H. Ritzwoller Department of Geology University of Illinois at Urbana-Champaign Urbana IL 61801 USA Institute of Earthquake Science China Earthquake Administration Beijing 100036 China CIEI Department of Physics University of Colorado at Boulder Boulder CO 80309 USA

We determine the three-dimensional shear wave velocity structure of the crust and upper mantle in China using Green＇s functions obtained from seismic ambient noise cross-correlation. The data we use are from the China National Seismic Network, global and regional networks and PASSCAL stations in the region. We first acquire cross-correlation seismograms between all possible station pairs. We then measure the Rayleigh wave group and phase dispersion curves using a frequency-time analysis method from 8 s to 60 s. After that, Rayleigh wave group and phase velocity dispersion maps on 1°by 1°spatial grids are obtained at different periods. Finally, we invert these maps for the 3-D shear wave velocity structure of the crust and upper mantle beneath China at each grid node. The inversion results show large-scale structures that correlate well with surface geology. Near the surface, velocities in major basins are anomalously slow, consistent with the thick sediments. East-west contrasts are striking in Moho depth. There is also a fast mid-to-lower crust and mantle lithosphere beneath the major basins surrounding the Tibetan plateau （TP） and Tianshan （Junggar, Tarim, Ordos, and Sichuan）. These strong blocks, therefore, appear to play an important role in confining the deformation of the TP and constraining its geometry to form its current triangular shape. In northwest TP in Qiangtang, slow anomalies extend from the crust to the mantle lithosphere. Meanwhile, widespread, a prominent low-velocity zone is observed in the middle crust beneath most of the central, eastern and southeastern Tibetan plateau, consistent with a weak （and perhaps mobile） middle crust.

关键词： ambient noise surface wave tomography crust and upper mantle China

Composition of high frequency ambient noise from cross-correlation:A case study using a small aperture array

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Earthquake Science 2010年第5期23卷 433-438页

作者： Weitao Wang Sidao Ni Baoshan Wang Institute of Geophysics China Earthquake Administration Beijing 100081 China Mengcheng National Geophysical Observatory School of Earth and Space Science University of Science and Technology of China Hefei 230026 China

Long-time cross correlation of ambient noise has been proved as a powerful tool to extract Green＇s function between two receivers. The study of composition of ambient noise is important for a better understanding of this method. Previous studies confirm that ambient noise in the long period （3 s and longer） mostly consists of surface wave, and 0.25-2.5 s noise consists more of body waves. In this paper, we perform cross correlation processing at much higher frequency （30-70 Hz） using ambient noise recorded by a small aperture array. No surface waves emerge from noise correlation function （NCF）, but weak P waves emerge. The absence of surface wave in NCF is not due to high attenuation since surface waves are strong from active source, therefore probably the high ambient noise mostly consists of body wave and lacks surface wave. Origin of such high frequency body waves in ambient noise remains to be studied.

关键词： ambient noise cross correlation Green＇s function body wave high frequency