Three-dimensional P-wave velocity structure of the crust beneath Hainan Island and its adjacent regions, China

Abstract

Using over 3 500 first P arrival times recorded by nine digital seismic stations from Hainan Digital Seismic Network during 1999~2005, a 3-D P-wave velocity model of the crust under Hainan Island and adjacent regions has been determined. The results show that the pattern of velocity anomalies in the shallower upper crust is somewhat associated with the surface geological tectonics in the region. A relative low-velocity anomaly appears north of the Wangwu-Wenjiao fault zone and a relative high-velocity anomaly appears south of the Wangwu-Wenjiao fault zone, corresponding to the depressed areas in north Hainan Island, where many volcanoes are frequently active and geothermal values are relatively higher, and the uplifted and stable regions in central and south of the Hainan Island. In the middle and lower crust velocities are relatively lower in east Hainan than those in west Hainan, possibly suggesting the existence of the upwelling of hot materials from the mantle in east Hainan. The pattern of velocity anomalies also indicates that NW faults, i.e., the Puqian-Qinglan fault, may be shallower, while the E-W Wangwu-Wenjiao fault may be deeper, which perhaps extends down to Moho depth or deeper.

Pn Anisotropic Tomography of Hainan Island and Surrounding Areas: New Insights Into the Hainan Mantle Plume

“…Many researchers have investigated the crustal and upper mantle Vp and anisotropy structures in the Hainan and surrounding areas, and displayed distinct low-V anomalies in the crustal and upper mantle under the Leiqiong areas (e.g., H. Chen et al, 2021;J. Huang, 2014;Lei, Zhao, Steinberger, et al, 2009;X. Li et al, 2008X.…”

“…Many researchers have investigated the crustal and upper mantle Vp and anisotropy structures in the Hainan and surrounding areas, and displayed distinct low‐V anomalies in the crustal and upper mantle under the Leiqiong areas (e.g., H. Chen et al., 2021; J. Huang, 2014; Z. Huang & Xu, 2011; Lei, Zhao, Steinberger, et al., 2009; X. Li et al., 2008, 2017; Mi et al., 2021; Tian et al., 2021; F. Wei et al., 2020; Xia et al., 2016; Y. Xu et al., 2007; X. Yang et al., 2021). However, the low‐V anomaly in the models of Xia et al.…”

“…Especially, active Quaternary volcanism and intensive seismicity took place along the Wangwu‐Wenjiao fault (e.g., Lei, Zhao, Steinberger, et al., 2009; Zhang & Zhao, 1984). The NW‐SE trending faults are a group of seismogenic faults, whose intersections with the E‐W trending faults led to the occurrence of large earthquakes, such as the 1605 M 7.5 Qiongshan earthquake (e.g., Jia et al., 2006; Lei, Zhao, Steinberger, et al., 2009; Z. Li et al., 2008).…”

Seismic evidence of the Hainan mantle plume by receiver function analysis in southern China

“…Although the velocity models are indicative of the complexities of the Lei‐Qiong crust, the nonuniqueness of this inversion [ Ammon et al ., ] prevents the inverted velocity results from being used as more than reference models for migration and stacking in the following step. Therefore, we only inverted the S wave velocity structure beneath station QIZ as a representative of Hainan Island, because this island is a relatively uniform unit with a roughly consistent velocity structure of the crust [ Li et al ., ].…”

The Magmatic Patterns Formed by the Interaction of the Hainan Mantle Plume and Lei–Qiong Crust Revealed through Seismic Ambient Noise Imaging

“…While several geophysical studies have provided constraints on the near-surface structure (e.g., [13,[36][37][38][39][40]), ongoing debate surrounds the nature of the interaction between the plume and the crust in the eastern Qiongzhou Strait and northernmost Hainan, referred to as the Hainan hotspot. Specifically, the mechanisms through which rising mantle materials interact with the crust, linking surface volcanism to deeper lithospheric processes, remain uncertain.…”