Preliminary study on Moho reflection wave based on noise interference method and its application in crustal structure imaging of the northeastern margin of the Qinghai–Xizang Plateau

Based on the continuous waveform records of the dense seismic array deployed in the northern section of the north–south seismic belt, Moho reflected PmP waves on the northeast edge of the Qinghai–Xizang Plateau were obtained using array noise interferometry technology. The existing regional 3D crustal velocity model was used to establish the initial 3D crustal model of the study area using the sedimentary layer correction method. The noise cross-correlation function was then corrected for the reference plane, and the crustal thickness distribution of the study area was obtained using the common midpoint stacking method. The results revealed a significant difference in crustal thickness between different blocks on the northeast edge and surrounding areas of the Qinghai–Xizang Plateau. The crustal thickness decreases gradually along the northeast extension direction of the plateau. The crustal thickness of the middle and western sections of the Qilian Orogenic Belt is about 55–65 km. The thickness of the western Qinling Orogenic Belt decreases from about 53 km to about 42 km from west to east. The crustal thickness of the Alxa Block is about 50 km, and the result for the western edge of the Ordos Block is between 40 and 45 km. Local crustal thickening was observed near the Liupanshan Fault, Haiyuan Fault, and Tianjingshan Fault, with pulse Moho surface reflection phases indicating the possible existence of Moho structures with significant velocity jumps near the fault zone. The overlapping reflection phases of the fault on the northern edge of the Qilian Mountains may have formed by thrust superimposition of the lower crust.