JOINT INVERSION OF RAYLEIGH WAVE VERTICAL-HORIZONTAL AMPLITUDE RATIOS AND DISPERSION BASED ON THE NEIGHBORHOOD ALGORITHM AND ITS APPLICATION

Abstract

Rayleigh wave ellipticity (or ZH ratio) is a function of frequency and is particularly sensitive to shallow crustal structure beneath the seismograph station. Since the depth sensitivity kernels of ZH ratios are different from those of dispersion data, the ZH ratio provides good complementary information for the dispersion-based inversion method. Therefore, we can combine the ZH ratio and dispersion data of Rayleigh wave fundamental mode to better invert for the velocity structure under a specific seismograph station. In this paper, we propose a joint inversion method using the dispersion and ZH ratio data based on the Neighborhood Algorithm. We conduct synthetic tests based on a theoretical model and prove the robustness of the joint inversion method, which can better constrain the shallow crustal structure. Compared to traditional inversion methods that only use dispersion data, the joint inversion can provide a more accurate crustal V_s model as well as V_p/V_s ratios for the layered crust. Finally, we apply the joint inversion technique to real measurements and obtain a more accurate crust shear velocity and V_p/V_s model beneath the station at Kunming (KMI) in southwest China.