Ambient Noise Tomography of the Shandong Province and its Implication for Cenozoic Intraplate Volcanism in Eastern China

Abstract

New images of shear wave velocity (VS) structure of the crust and uppermost mantle in the Shandong province of China are presented based on inversion of ambient seismic noise data from 47 broadband stations. Interstation Rayleigh wave phase-velocity dispersion curves for periods of 1–40 s are obtained from noise cross correlations between stations. Two-dimensional phase-velocity maps at periods of 5–30 s are obtained by tomographic inversion of these dispersion curves, which are then inverted for 3-D Vs heterogeneity to ~80-km depth. Our results show clear indications of Moho uplift and crustal thinning beneath the northern segment of the Yishu fault zone and the Jiaobei uplift, thus providing seismological evidence for the steep geometry and deep penetration of the fault system. Instead of large-scale, low-velocity anomalies beneath eastern China as imaged by previous regional tomography, our high-resolution Vs results reveal fine-scale focused low-velocity anomalies beneath the isolated Cenozoic basalts. There are strong spatial correlations between the narrow low Vs zones in the uppermost mantle and the thinned crust, as well as the locations of the isolated Cenozoic volcanism in the study area. Our results suggest that the asthenosphere upwelling possibly originating from the stagnant Pacific slab is focused into localized features at 50- to 80-km depth that supply the isolated Cenozoic volcanoes of the eastern China continental margin.