Rayleigh wave group velocity distribution in Ningxia

In this article, seven months ambient noise data and 10 events recorded at seven digital stations from the Ningxia (宁夏) regional seismic network and 5 500-t controlled source explosion data recorded by 15 temporary and 7 permanent seismic stations are used to measure dispersion curves of fundamental mode Rayleigh waves. The study region was divided into grids with 0.1°×0.1°; group velocity distributions of Rayleigh waves from 6–22 s were determined with the Occam’s inversion technique. These velocity distribution maps show the lateral velocity variations in the study area, and the velocity structures are correlated with surface geology and tectonic units. The Yinchuan (银川) basin is clearly featured with low velocities, and the Helan (贺兰) Mountain and southern mountain areas are revealed with high velocities.