3D Vs ambient noise tomography of the 2016 Mw 6.4 Meinong Earthquake source region in Taiwan

Abstract

Mw 6.4 Meinong earthquake occurred on 6 February 2016 in southern Taiwan, resulting in more than one hundred casualties and several collapsed buildings. The aftershocks occurred mostly at mid-to-lower crustal depths (10 - 30 km), related to a blind fault system. However, several centimeters of cosesimic surface uplift within the Liushuang, Erhchungli, and GutingKeng Formations, composed mainly of mudstone, was recorded from the InSAR results. The uplifted pattern is similar to that of GPS and leveling data from 2000 - 2010, which indicates the deformation is accomplished by creeping due to the shallow mudstone structure related to mud diapir. Previous studies have shown limited information about the shallow structure in this region due to few deployed seismic stations. We deployed 36 temporary seismic stations (~5 km spacing) in this study around one month after the main shock to obtain a 3-D shear wave shallow crustal velocity structure using ambient noise tomography. The reliable periods of group and phase velocities from Rayleigh waves were 0.6 - 5 s, corresponding to around 0 - 5 km at depths. As a result, the low S-wave pattern speeds at 0 - 4 km depths correspond to the uplift region from both InSAR data for the coseismic period and GPS and leveling data for the interseismic period. The results from this study are compatible with the reflected seismic profile. The results show that with dense seismic array deployment we can obtain high subsurface image resolution to link the relationship between the surface observations to the subsurface structures.