scholarly journals Shear wave tomography of China using joint inversion of body and surface wave constraints

2012 ◽  
Vol 117 (B1) ◽  
pp. n/a-n/a ◽  
Author(s):  
Mathias Obrebski ◽  
Richard M. Allen ◽  
Fengxue Zhang ◽  
Jiatie Pan ◽  
Qingju Wu ◽  
...  
Keyword(s):  
Surface Wave ◽  
Shear Wave ◽  
Joint Inversion ◽  
Wave Tomography

scholarly journals Shear Wave Tomography Beneath the United States Using a Joint Inversion of Surface and Body Waves

2018 ◽  
Vol 123 (6) ◽  
pp. 5169-5189 ◽  
Author(s):  
E. M. Golos ◽  
H. Fang ◽  
H. Yao ◽  
H. Zhang ◽  
S. Burdick ◽  
...  
Keyword(s):  
United States ◽  
Shear Wave ◽  
Joint Inversion ◽  
The United States ◽  
Body Waves ◽  
Wave Tomography

Direct inversion of 3-D shear wave speed azimuthal and radial anisotropy from surface-wave traveltime data: methodology and applications

2020 ◽  
Author(s):  
Yao Huajian ◽  
Liu Chuanming ◽  
Hu Shaoqian
Keyword(s):  
Surface Wave ◽  
Shear Wave ◽  
Wave Speed ◽  
Joint Inversion ◽  
Azimuthal Anisotropy ◽  
Crust And Upper Mantle ◽  
Shear Wave Speed ◽  
Dispersion Data ◽  
Radial Anisotropy ◽  
Deformation Patterns

<p>Seismic anisotropy plays a key role in understanding deformation patterns of Earth’s material.  Surface wave dispersion data have been widely used to invert for azimuthal and radial anisotropy of shear wave speeds in the crust and upper mantle typically based on a 1-D pointwise inversion scheme. Here we present new methods of inverting for 3-D shear wave speed azimuthal and radial anisotropy directly from surface-wave traveltime data with the consideration of period-dependent surface wave raytracing. For the inversion of 3-D azimuthal anisotropy, our new method includes two steps: (1) inversion for the 3-D isotropic Vsv model directly from Rayleigh wave traveltime data (DSurfTomo; Fang et al., 2015, GJI); (2) joint inversion for both 3-D Vsv azimuthal anisotropy and additional 3-D isotropic Vsv perturbation. The joint inversion can significantly mitigatethe trade-off between the strong heterogeneity and azimuthal anisotropy. We apply the new method (DAzimSurfTomo) (Liu et al., 2019, JGR)to a regional array in Yunnan, southwestern China using the Rayleigh-wave phase velocity dispersion data in the period band of 5-40 s extracted from ambient noise interferometry. The obtained 3-D model of shear wave speed and azimuthal anisotropy indicates differentdeformation styles between the crust and upper mantle insouthern Yunnan. For the inversion of 3-D radial anisotropy, we presented a new inversion matrix that directly inverts Rayleigh and Love wave traveltime data jointly for 3-D Vsv and radial anisotropy parameters (Vsh/Vsv) simultaneously without intermediate steps (Hu et al., submitted to JGR).  The new approach allows for adding the smoothing or model regularization terms directly on the radial anisotropy parameters, which helps to obtain more reliable radial anisotropy structures compared to the previous division approach (Vsh/Vsv) from separate inversion of Vsv and Vsh structures. We apply this new approach (DRadiSurfTomo) to the region around the eastern Himalayan syntaxis using ambient noise dispersion data (5-40s). The obtained 3-D Vs and radial anisotropy models reveals complex distribution of crustal low velocity zones and spatial variation of deformation patterns around the eastern syntaxis region.</p>

Seismic Surface Wave Tomography on dense 3D active data

2020 ◽  
Author(s):  
Ilaria Barone ◽  
Emanuel Kästle ◽  
Claudio Strobbia ◽  
Giorgio Cassiani
Keyword(s):  
Surface Wave ◽  
Phase Velocity ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Seismic Exploration ◽  
Surface Wave Tomography ◽  
Travel Times ◽  
Velocity Models ◽  
Wave Tomography

<p>Surface Wave Tomography (SWT) is a well-established technique in global seismology: signals from strong earthquakes or seismic ambient noise are used to retrieve 3D shear-wave velocity models, both at regional and global scale. This study aims at applying the same methodology to controlled source data, with specific focus on 3D acquisition geometries for seismic exploration. For a specific frequency, travel times between all source-receiver couples are derived from phase differences. However, higher modes and heterogeneous spatial sampling make phase extraction challenging. The processing workflow includes different steps as (1) filtering in f-k domain to isolate the fundamental mode from higher order modes, (2) phase unwrapping in two spatial dimensions, (3) zero-offset phase estimation and (4) travel times computation. Surface wave tomography is then applied to retrieve a 2D phase velocity map. This procedure is repeated for different frequencies. Finally, individual dispersion curves obtained by the superposition of phase velocity maps at different frequencies are depth inverted to retrieve a 3D shear wave velocity model.</p>

Rapid Post-Earthquake Microtremor Measurements for Site Amplification and Shear Wave Velocity Profiling in Kathmandu, Nepal

2017 ◽  
Vol 33 (1_suppl) ◽  
pp. 55-72 ◽  
Author(s):  
Sheri Molnar ◽  
John Onwuemeka ◽  
Sujan Raj Adhikari
Keyword(s):  
Surface Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Joint Inversion ◽  
Ambient Vibration ◽  
Site Classification ◽  
Source Surface ◽  
Individual Measurement ◽  
Site Period

This paper presents application of microtremor (ambient vibration) and surface wave field techniques for post-earthquake geotechnical reconnaissance purposes in Kathmandu, Nepal. Horizontal-to-vertical spectral ratios (HVSR) are computed from microtremor recordings at 16 individual measurement locations to obtain an estimate of fundamental frequency (site period) of the subsurface soils. A combination of active- and passive-source surface wave array testing was accomplished at five key sites including Kathmandu's Durbar Square and Airport. Joint inversion of each site's higher frequency dispersion and lower frequency HVSR data sets provides an estimate of subsurface material stiffness [i.e., shear wave velocity ( V S) depth profiles]. Direct comparison of our V S profiling at Kathmandu Durbar Square and that accomplished by downhole V S and/or standard penetration testing (SPT) profiling yield similar results. Classification of the five sites based on average V S, site period, and/or basin depth is presented. There is little differentiation in these site classification designations amongst the five sites, which does not capture significant differences in observed earthquake damage.

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