2012 IRIS Workshop
Anisotropic Upper Mantle Shear-wave Structure of East Asia from Waveform Inversion
Jiajun Chong: UC Berkeley-Berkeley Seismological Laboratory and Univ. of Sci. & Tech. of China, Huaiyu Yuan: UC Berkeley-Berkeley Seismological Laboratory, Scott French: UC Berkeley-Berkeley Seismological Laboratory
Depth cross sections and 150-km map view of the isotropic Vs perturbation, showing well correlation with surface tectonics in East Asia.The map view shows dominant fast (west) and slow (east) velocity domains separated by Altai/Qilian orogenic belts. Cross sections show distinct subduction pattern of the Indian lithosphere between the western (AA') and eastern (BB') parts, each with different angle and northern reach. BB' also indicates clear subduction of the Asian lithosphere.
Full-resolution graphics file in original format: 0134.ai
East Asia is a seismically active region in the world which is surrounded by active tectonic belts, such as the Himalaya collision zone, western Pacific subduction zones and the Tianshan- Baikal tectonic belt. In this study, we applied full waveform time domain tomography to image 3D isotropic and anisotropic upper mantle shear velocity structure of East Asia. High quality seismic waveforms are collected for both permanent and temporary stations in target and its adjacent regions, which provide good ray path coverage of the study region with a combination of global data-set. Fundamental and overtone wave packets, filtered down to 60 s, are inverted for isotropic and anisotropic shear wave structure using normal mode asymptotic coupling theory (NACT: Li and Romanowicz, 1995). The preliminary 3D shear velocity model shows strong lateral heterogeneities in the region, which correlate well with surface geology in East Asia.
Acknoweldgements: This work was supported by NSF grant EAR-0738284.
For further reading: Chong J.J, Yuan H.Y., French, S.W., B. Romanowicz, Ni S.D. (2011), Imaging 3D anisotropic upper mantle shear velocity structure of Southeast Asia using seismic waveform inversion, T33B-2409, 2011 Fall Meeting, AGU, San Franciso.
Keywords: east_asia, upper-mantle_structure, anisotropy, waveform_inversion