Love wave phase velocity tomography in the south-central Mongolia from earthquakes

This paper utilized the data from broadband seismic arrays of the China-Mongolia cooperative project， and extracted the fundamental mode Love wave phase velocity dispersion curves along the 901 two-station paths in the south-central Mongolia by the wavelet transformation method. These phase velocity dispersion curves were applied to construct the 2-D Love wave phase velocity maps for the period range of 12--80 s with horizontal resolution about 50 km in the area. The distribution of phase velocity show that horizontal heterogeneity exists in the studied area. The phase velocity distributions at shorter periods (12--20 s) are obviously controlled by geologic units， for example， Hangay-Hentiy mountain basin exhibits high velocity anomaly while Ulaanbaatar basin， middle Gobi and southern Gobi desert exhibit low velocity anomaly. In the period range of 20--40 s， the features of phase velocity distribution are similar to those for shorter periods， but the amplitude of horizontal heterogeneity becomes weaker. At longer periods (40--70 s)， the southern Gobi and Hangay-Hentiy mountain basin show low velocity anomaly while the middle Gobi shows high velocity anomaly， which is distinctly different from that by Rayleigh wave phase tomography. The whole areas present the shape of low velocity anomaly in north and south and high velocity anomaly in middle. Therefore， combined with broad distribution of Cenozoic volcanic rocks in the middle Gobi， it is deduced that the stronger radial anisotropy exists in the studied area.