A thinned lithosphere beneath coastal area of southeastern China as evidenced by seismic receiver functions

Abstract

During Mesozoic to Cenozoic time, the large-scale tectono-magmatism had strongly modified the lithosphere beneath the southeastern continent of China, leaving the present-day lithosphere as a new one evolving from the ancient lithosphere that was largely removed and replaced. But this model proposed from geochemical and petrological research is urgently in need of support from seismic observational evidence. In this paper, based on the dataset recorded by the dense stations of two NE ori- ented broadband seismic profiles deployed in the coastal area of southeastern China (SE China), both P-wave (P-RF) and S-wave (S-RF) receiver functions were isolated. We identified Pls phase converted from the Lithosphere-Asthenosphere Boundary (LAB) in P-RFs of individual stations. Migrated Pls phase indicated a depth of 60–70 km for LAB. Inver- sions/comparisons of P-RF (Pls phase) and S-RF (Slp phase) waveforms together with Ps and Sp imaging for the crust and up- per mantle structure further confirmed this result. P-RF and S-RF migrated images exhibit that a flat LAB is positioned at the depth of 60–70 km spreading along the profile, whereas a distinct structural change of lithospheric base appears at the Min River estuary. Both Ps and PpPs migrated images of P-RFs present an abrupt Moho drop across the Min River fault from south to north, which is consistent with previous result obtained from deep seismic sounding. By taking into consideration other ge- ological and geophysical features such as locally high anomalies of crustal Poisson’s ratios and heat flow at the Min River es- tuary, we infer that the Min River fault penetrates down to the Moho and may, furthermore, interfere in the deeper lithospheric structure.