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.

Cenozoic Evolution of the Bohai Bay Basin: Constraints From Seismic Radial Anisotropy

“…Our models support this notion by revealing a shallow Moho depth (<28 km, more details can be found in Text S4 and Figure S12 of the Supporting Information ) and high S‐wave velocity anomalies in the uppermost mantle beneath Bohai Sea (Figures 2c and 3d). Previous studies (C. Li et al., 2018; C. L. Li et al., 2022; Pang et al., 2017) suggest that mantle‐heat flow from the upper mantle has permeated and risen along the Tanlu fault, potentially reaching the lower crust and forming a high‐velocity zone after prolonged cooling and solidification. Therefore, our findings lead further support to the opinion of underplating by mantle material beneath the Bohai Sea, with the Tanlu fault zone facilitating the upwelling of hot asthenospheric material (L. Chen et al., 2006; Hao et al., 2013; Jia et al., 2014; C. L. Li et al., 2022; L. Liu et al., 2015; T. Zheng et al., 2006).…”