[S-IT30] [EE] Characterizing/contrasting seismic discontinuities in the oceanic and continental lithosphere

[SIT30-03] Moho Depth Variations in the northeastern North China Craton Revealed by Receiver Function Imaging

*Huajian Yao¹、Ping Zhang¹、Ling Chen²、Yan Wu³、Lihua Fang³ (1.University Science & Technology of China、2.Institute of Geology and Geophysics, Chinese Academy of Sciences、3.Institute of Geophysics, China Earthquake Administration)

キーワード：Moho discontinuity, North China Craton, Lithospheric destruction, Receiver function imaging

The North China Craton (NCC), one of the oldest cratons in the world, has attracted wide attention in Earth Science for decades because of the unusual Mesozoic destruction of its cratonic lithosphere. Understanding the deep processes and mechanism of this craton destruction demands detailed knowledge about the deep structure of the region. In this study, we used two-year teleseismic receiver function data from the North China Seismic Array, which consists of ~200 broadband stations deployed in the northeastern NCC, to image the Moho undulation of this region. A 2-D wave equation-based poststack depth migration method (Chen et al., 2005) was employed to construct the structural images along 19 profiles, and a pseudo 3D crustal velocity model of the region based on previous ambient noise tomography and receiver function study was adopted in the migration. We considered both the Ps and PpPs phases, but in some cases we also conducted PpSs+PsPs migration, analyzed images using different back azimuth ranges of the data, and calculated the theoretical travel times of all the considered phases to constrain the Moho depths. By combining the structure images along the 19 profiles, we got a high-resolution Moho depth map beneath the northeastern NCC. Generally, the Moho depths are distinctly different on the opposite sides of the North-South Gravity Lineament. The Moho in the west are deeper than 40 km and shows a rapid uplift from ~40 km to ~30 km beneath the Taihang Mountain Range in the middle. To the east in the Bohai Bay Basin, the Moho further shallows to ~30-26 km depth and undulates by ~3 km, coinciding well with the depressions and uplifts inside the basin. The Moho depth beneath the Yin-Yan Mountains in the north gradually decreases from ~42 km in the west to ~35 km in the east, varying much smoother than that to the south. Our results broadly consist with the pattern of previous active source studies [http://www.craton.cn/data], and show a good correlation of the Moho depths with geological and tectonic features. We systematically compared our results with other seismic observations and discussed correlations of Moho depths with lithospheric thickness, seismic anisotropy, surface geology, reginal tectonics, and gravity anomaly as well as petrographic and geochemical data in detail. Furthermore, we discussed possible mechanisms accounting for fundamental destruction of the NCC lithosphere in Late Mesozoic.