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During the early Cenozoic, the collision and convergence between India and Eurasia resulted in the uplift of the Tibetan Plateau and continuous northward compression, forming the Circum‐Tibetan Plateau Basin and Orogen System (CTPBOS). The Tarim Basin, located between the Tibetan Plateau and the Tianshan Mountains, plays a crucial role for studying the convergence‐driving strain propagation mechanism intra‐Asian continent during the growth processes of the Tibetan Plateau. Owing to the lack of accurate geophysical information on the deep structure of the Tarim crust，the mechanism of Cenozoic deformation in the Tarim Basin has been under debate. In this paper, the teleseismic data acquired by the broadband seismic profile across the Tarim Basin from south to north and the S‐wave receiver function method were used to obtain the depth of the Moho and the discontinuities in the lithosphere beneath the Tarim Basin. The SRF result shows that the Moho geometry has an abrupt relief under the Bachu Uplift, and Moho offset under the fault zone between the Kalashayi Fault and the Tumuxiuke Fault. The regional dip of the Moho under the Bachu area can be explained by the root of the Bachu basement‐involved uplift cutting across the whole crust and locally penetrating into the mantle lithosphere. The Bachu Uplift, located in the central Tarim terrane, has a relatively weak lithosphere. In the process of forming the Tarim large igneous province during the early Permian, the crust beneath the Bachu area was weakened and thinned by the thermo‐mechanical erosion from upwelling mantle plume. As the collision and convergence of India and Eurasia since the early Cenozoic, the convergence‐driving strain was propagated into the Tarim Basin. The pre‐existing weak Bachu Uplift was reactivated. The Tarim Basin absorbs Cenozoic compressional deformation through the crustal shortening and Moho offset of the Bachu Uplift. [ABSTRACT FROM AUTHOR]

Large earthquakes that occur away from plate boundaries (i.e., large intraplate earthquakes), though rare, could cause heavy damage. Understanding their causes could help with seismic hazard assessment. In this study, we image the seismogenic structure under the 1969 Ms6.4 Yangjiang intraplate earthquake within the stable South China Block with a high‐resolution three‐dimensional shear‐wave velocity model constructed from ambient noise tomography based on a dense nodal seismic array. The model images relatively low velocities at a fault intersection region from the surface to at least 13 km depth in the Yangjiang seismogenic zone. Given spatial links among the intersection zone of faults, surface seawater, and low velocities, we interpret the low velocities to reflect the presence of seawater‐filled, highly fractured rocks created by the intersection of faults. We infer that the seawater infiltration through densely‐fractures could have elevated pore pressure in the long term, as evidenced by low earthquake b values at 8–13 km depths. We hypothesize that this long‐term seawater infiltration could have lowered the stress threshold of earthquake occurrence and contributed to the generation of the 1969 Ms6.4 Yangjiang earthquake. We propose that the large intraplate earthquakes within stable plates tend to occur in regional weakening regions (e.g., fault intersections) favorable to stress buildup. Given sufficient tectonic stress accumulation, the long‐term hydrologically driven crustal stress variations could play an essential role in triggering large intraplate earthquakes. This study could potentially contribute to improving seismic hazard assessment in the Guangdong‐Hong Kong‐Macao‐Greater‐Bay‐Area, China. Plain Language Summary: Large earthquakes usually occur at boundaries between two tectonic plates (i.e., interplate earthquakes). Away from a plate boundary, some large earthquakes, though rare relative to the interplate earthquakes, could occur within the interior of plates (i.e., intraplate earthquakes), such as the most notable Mw > 7.0 New Madrid earthquakes in 1811–1812. Why and how these large intraplate earthquakes occurred remain enigmatic. The Yangjiang region (South China) that hosted the 1969 Ms6.4 Yangjiang intraplate earthquake is one of the best places to study the causes of intraplate earthquakes. This study uses ambient noise tomography to image a low‐seismic‐velocity "chimney" (in the upper crust to 13 km depth) along the seismogenic fault zone. We interpret this low‐velocity "chimney" as a path for seawater infiltration through dense fractures created by the intersection of faults. The fault intersection zone at depths of 8–13 km is a favorable place for stress buildup, as indicated by low earthquake b‐values. We further hypothesize that seawater infiltration in the long term could have lowered effective stress through elevating pore pressure, probably explaining the cause of the Ms6.4 Yangjiang earthquake. We propose that long‐term hydrologically driven crustal stress variations could be essential in triggering large intraplate earthquakes given sufficient tectonic stress accumulation. Key Points: An upper crustal seismic shear‐wave velocity model was constructed under the 1969 Ms6.4 Yangjiang earthquake in South ChinaAmbient noise tomography images low velocities under the 1969 Yangjiang earthquake seismogenic regionWater‐filled dense fractures in fault zones can probably explain the presence of low velocities [ABSTRACT FROM AUTHOR]

[Display omitted] • A dense seismic array deployed 18 days is used to image a 3D Vs model. • Three LVZs are revealed in the shallow crust beneath the Shiziyang Waterway area. • Three cross-cutting fault zones in the sedimentary basement are identified. • Two-stage differential fault movements dominated the opening of the Shiziyang Waterway. The Shiziyang Waterway, located in the northern continental margin of the South China Sea, has developed a complex fault system owing to the coupling action of the oceanic crust and continental crust. However, the geological structure in the shallow crust beneath the Shiziyang Waterway and the relationship between faults and waterway development are still unclear, resulting in difficulty in assessing the earthquake risk to the surrounding cities. In this study, based on a high-density short-period seismic array that was recently deployed around the Shiziyang Waterway, a high-resolution shear wave velocity model is inverted to as shallow as 4 km by the ambient noise tomography method. The results showed that at depths ranging from 0.2 to 4 km, three sets of low-velocity zones (LVZs), trending east–west, northeast, and northwest, are revealed, which are speculated to be the Shougouling fault (SGLF), Xinhui-Shiqiao fault (XSF), and Shiziyang fault bundle (SZYFb), respectively. The shear-wave velocity anomalies illustrate that the SGLF stopped extending east at the north endpoint of the Wenchong-Zhujiangkou fault (WZF). The two-stage differential vertical movements of the WZF, Nangang-Humen fault (NHF), and Hualong-Haioudao fault (HHF) dominated the opening of the Shiziyang Waterway. This study provides new seismological evidence of the opening process for the Shiziyang Waterway and reveals that internal fault activity dominated the development and evolution of the Pearl River Delta. [ABSTRACT FROM AUTHOR]