High resolution 3D Sv wave velocity model of China and surrounding area

In our study we determine the three dimensional Sv wave speed and azimuthal anisotropy model by analyzing vertical component multimode Rayleigh wave seismograms. We use data of broadband stations from in and around China. We construct the three dimensional model using a two step procedure. In the first step we use the automated version of the Cara and Leveque [1987] waveform inversion technique in terms of secondary observables for modeling each multimode Rayleigh waveform to determine the path-average mantle Sv wave speed structure. We have used the 3SMAC model (as a crustal part) and smooth version of PREM for the upper mantle velocity structure as an initial model. In the second stage we combine the 1-D velocity models in a tomographic inversion to obtain the three dimensional Sv wave speed structure and the azimuthal anisotropy as a function of depth. China is sitting at a triple junction of three major plates: the Eurasian plate, the Indo-Australian plate and the Philippine Sea plate. China itself has three major Precambian cratons: the North China craton (also called Sino-Korean craton), the Yangtze craton (also called South China craton) and the Tarim block. The interactions among different blocks have formed the tectonic features today and caused many intraplate earthquakes. These tectonics setting have made China an interesting place for various kind of study as all of these events have left their imprint on the upper mantle structure. It is generally agreed that the lithosphere is thick in west China while much of the lithospheric root was lost beneath some cratons in east China. Still it's an open debate whether the lithosphere beneath the Tibetan plateau has doubled its thickness as did the crust above or much of the thickened lithosphere was removed by mantle convection and delamination. The upper most part of our model is in good agreement with the finding from the deep seismic profile. It is also evident that the extent of crustal flow of Tibet is being restricted by Tarim in the north and Ordos, Sichuan in the east. Various receiver function and SS precursor results are also comparable with our results in terms of the lithosphere extent.