Crustal thickness and average Vp/Vs ratio variations in southwest Yunnan, China, from teleseismic receiver functions

Abstract

Recently, many portable broadband three-component seismic stations have been deployed in Yunnan, China. We use teleseismic receiver functions to determine the crustal thickness (H) and the crustal average compressional to shear wave velocity (Vp/Vs) ratio (k) variations beneath in southwest Yunnan. By comparing the synthetics generated from dipping Moho models with those from a flat Moho model, it reveals that for the rays traveling along or around the updip direction, the differential arrival times of Ps and multiples generated at the dipping Moho are comparable with those generated at the flat Moho and the result from stacking with these synthetics is a better estimate of model structure. For the synthetics traveling along or around the downdip direction, the differential arrival times of Ps and multiples generated at dipping Moho are smaller than those generated at flat Moho and make the H-k stacking results deviate from the model structure. Thus, the ambiguity induced by dipping Moho can be reduced significantly by only stacking with the rays traveling along or around the updip direction. Applying this technique to 19 stations, we obtained that H ranges from ∼35-42 km and the k ranges from ∼1.66-1.78. From the central Simao basin, H increases northward and northeastward; k increases significantly northeastward across the Ailao Shan-Red River shear zone. © 2010 by the American Geophysical Union.