scholarly journals Seismic-velocity inversion using surface-wave tomography

Author(s):  
Zheshu Wu ◽  
James Rector
2020 ◽  
Author(s):  
Petr Kolínský ◽  
Tena Belinić ◽  
Josip Stipčević ◽  
Irene Bianchi ◽  
Florian Fuchs ◽  
...  

<p>The Alpine-Dinarides are a complex orogenic system, with its tectonic evolution controlled by the ongoing convergence between Eurasian and African plates with the Adriatic microplate wedged between them. Our study focuses on the upper mantle of the wider Alpine-Dinarides region, and we present surface-wave tomography of two overlapping subregions, interpreting the seismic velocity features in the context of regional geodynamics.</p><p>In the first part, we use records of 151 teleseismic earthquakes (2010-2018) at 98 stations distributed across the wider Dinarides region. Surface-wave phase velocities are measured in the range of 30 – 160 s by the two-station method at pairs of stations aligned along the great circle paths with the epicenters. We apply several data-quality tests before the dispersion curves are measured. We use Rayleigh waves recorded on both radial and vertical components. Only the dispersions measured coherently at both components are used for the tomography. In total, we reach the number of 9000 phase velocity measurements for the period of 50 s. Tomographic results including resolution estimates are provided for various frequencies; the local dispersion curves are inverted for depths from the surface down to 300 km. Results are shown as maps for various depths and as cross-sections along several profiles of shear-wave velocities in the whole region.</p><p>The other study focuses on the Alps. The AlpArray seismic network stretches hundreds of kilometers in width and more than thousand kilometers in length. It is distributed over the greater Alpine region (Europe) and consists of around 250 temporary and around 400 permanent broadband stations with interstation distances around 40 km. The earthquakes are selected between years 2016-2019. The methodology differs from the Dinarides case in a sense, that while before we used many earthquakes and less stations pairs (due to sparser station coverage), for the Alps, we use less earthquakes (32) and many more stations pairs (tens of thousands) making use of the dense station coverage of the AlpArray network.</p><p>Results of the depth inversion of the local dispersion measurements for the Alps are compared with local surface-wave phase-velocity measurement obtained from the (sub)array approach.</p>


2020 ◽  
Vol 224 (2) ◽  
pp. 1287-1300
Author(s):  
Małgorzata Chmiel ◽  
Philippe Roux ◽  
Marc Wathelet ◽  
Thomas Bardainne

SUMMARY We propose a new surface wave tomography approach that benefits from densely sampled active-source arrays and brings together elements from active-source seismic-wave interferometry, full waveform inversion and dense-array processing. In analogy with optical interferometry, seismic Michelson interferometer (SMI) uses seismic interference patterns given by the data-based diffraction kernels in an iterative inversion scheme to image a medium. SMI requires no traveltime measurements and no spatial regularization, and it accounts for bent rays. Furthermore, the method does not need computation of complex synthetic models, as it works as a data-driven inversion technique that makes it computationally very fast. In an automatic way, it provides high-resolution phase-velocity maps and their error estimation. SMI can complete traditional surface wave tomography studies, as its use can be easily extended from land active seismic data to the virtual source gathers of ambient-noise-based studies with dense arrays.


2012 ◽  
Vol 4 (1) ◽  
pp. 1-31 ◽  
Author(s):  
P. Kumar ◽  
X. Yuan ◽  
R. Kind ◽  
J. Mechie

Abstract. The dense deployment of seismic stations so far in the western half of the United States within the USArray project provides the opportunity to study in greater detail the structure of the lithosphere-asthenosphere system. We use the S receiver function technique for this purpose which has higher resolution than surface wave tomography, is sensitive to seismic discontinuities and has no problems with multiples like P receiver functions. Only two major discontinuities are observed in the entire area down to about 300 km depth. These are the crust-mantle boundary (Moho) and a negative boundary which we correlate with the lithosphere-asthenosphere boundary (LAB) since a low velocity zone is the classical definition of the seismic observation of the asthenosphere by Gutenberg (1926). Our S receiver function LAB is at a depth of 70–80 km in large parts of westernmost North America. East of the Rocky Mountains its depth is generally between 90 and 110 km. Regions with LAB depths down to about 140 km occur in a stretch from northern Texas over the Colorado Plateau to the Columbia Basalts. These observations agree well with tomography results in the westernmost USA and at the east coast. However, in the central cratonic part of the USA the tomography LAB is near 200 km depth. At this depth no discontinuity is seen in the S receiver functions. The negative signal near 100 km depth in the central part of the USA is interpreted by Yuan and Romanowicz (2010) or Lekic and Romanowicz (2011) as a recently discovered mid lithospheric discontinuity (MLD). A solution for the discrepancy between receiver function imaging and surface wave tomography is not yet obvious and requires more high resolution studies at other cratons before a general solution may be found. Our results agree well with petrophysical models of increased water content in the asthenosphere, which predict a sharp and shallow LAB also in continents (Mierdel et al., 2007).


2007 ◽  
Vol 171 (3) ◽  
pp. 1098-1117 ◽  
Author(s):  
D. Peter ◽  
C. Tape ◽  
L. Boschi ◽  
J. H. Woodhouse

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