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

Abstract

Magmatism on continental lithospheres induced by mantle plumes is more complex compared to oceanic intraplate volcanism owing to the heterogeneous nature of continental crustal and lithospheric structures. Substantial evidence points to the deep-oriented Hainan mantle plume beneath the Lei–Qiong region, the southernmost of the South China block. In this study, we present a detailed shear wave velocity model of the crust and uppermost mantle in the Lei–Qiong volcanic region, derived from 3-year seismic data (2016–2018) from 34 stations and the use of the ambient noise tomography method. An evident columnar low-velocity anomaly was imaged in the crust and uppermost mantle beneath the Wushi Sag (WSS), Beibu Gulf, potentially suggesting that the center of either one branch or the entirety of the Hainan mantle plume impacts the crust here. This low-velocity anomaly is overlaid by a local Moho deepening, indicative of underplating beneath the existing crust. The Maanling–Leihuling Volcanic Field (MLVF) in northern Hainan Island, previously considered the center of the hotspot, does not exhibit such distinct velocity anomalies. Instead, subtle lower crustal anomalies beneath the MLVF are linked with the upper mantle low-velocity zone beneath the WSS. Additionally, the high-conductivity bodies beneath the MLVF indicate lateral magma transport. Earthquake swarms and deep-seated seismic events beneath the WSS further support the presence of magmatic processes. This study indicates that in the Lei–Qiong region, the interaction of the continental crust with the mantle plume centered in the WSS results in magma exhibiting both vertical ascent and lateral migration, leading to a dual low-velocity shear wave pattern in the upper crust, which significantly influences the surface volcanic activity.

SEISMONOISY: A Quasi-Real-Time Seismic Noise Network Monitoring System

“…In other research applications, however, the background signal is not seen as noise; in fact, there are several research applications that use natural seismic noise as a useful signal. Examples of applications of the use of background noise are imaging and land monitoring by obtaining Green’s functions between pairs of stations from the stack of their noise cross-correlograms [ 24 ], indirect subsurface exploration through ambient noise tomography [ 25 , 26 ], determination of significant ocean wave heights [ 27 ], determination of the response of the seismic amplification of a site through the HVSR technique [ 28 , 29 , 30 , 31 ], study of the temporal and spatial changes in the property statistics of seismic noise as a precursor or preparation for strong earthquakes [ 32 , 33 , 34 , 35 , 36 ], characterization of ambient seismic noise for improving the design of long-term seismograph installations [ 37 ], and spectral characteristics of the continuous seismic noise signals to understand the dynamics of a hydrothermal source [ 38 ].…”