Depth Extent and Vp/Vs Ratio of the Chenghai Fault Zone, Yunnan, China Constrained From Dense‐Array‐Based Teleseismic Receiver Functions

Abstract

AbstractFault zone (FZ) structure is critical for understanding earthquake rupture propagation and assessment of seismic hazard. In this study, we develop a new 2‐D dense‐array‐based inversion method to obtain high‐resolution FZ structure model using teleseismic receiver function. In our method, coherent travel times of converted waves and their multiples are first identified from teleseismic receiver functions; then the travel times are inverted for both depth extent and ratio beneath the seismic dense array. Synthetic tests with various shallow low‐velocity‐zone (LVZ) models demonstrate the effectiveness and robustness of our new method. We apply our method to the data recorded by a linear dense array across the southern segment of the Chenghai fault (CHF) in Yunnan, southwestern China. The inversion results suggest that the depth of the LVZ beneath the CHF extends to ∼1.1 km. Furthermore, we derive the ratio simultaneously and obtain the P‐wave velocity model from a S‐wave velocity model of the LVZ that were derived from ambient noise tomography. Travel times predicted by the newly obtained model are consistent with teleseismic P‐ and S‐wave arrivals. In addition, our method shows clear improvement in stability compared with the single‐station H‐ method. With dense seismic arrays deployed globally, our method would be a useful tool in shallow low‐velocity structure imaging studies, including fault zones and sedimentary basins.