Magma dynamics and subsurface structures in the Hainan volcanic field, China, and the relationship with seismic activity

SUMMARY The Hainan volcanic field (HNVF) is one of China’s most active Holocene volcanic areas. Due to a lack of comprehensive geophysical research, questions persist regarding the deep magma system of the HNVF. For example, it is unclear whether the intense seismic activity in its eastern part may be a precursor to renewed volcanic activity. We present new 3-D electrical conductivity images, derived from magnetotelluric data, that provide a new understanding of the deep magma system in the HNVF. Our results reveal the presence of multiple sets of low-resistivity structures in both shallow and deep regions. Although once associated with past volcanic activity, a widespread shallow low-resistivity layer on the northwest side of the HNVF is not currently indicative of shallow magma chambers. Instead, a deeper large-volume low-resistivity structure in the western part of the HNVF may represent the current crustal magmatic plumbing system. Our analysis suggests that the intense seismic activity in the east of HNVF lacks corresponding low-resistivity structures, which indicates that there is no direct correlation between seismicity and movement of magma. Recent volcanic eruptions are primarily concentrated near the Changliu–Xiangou fault, which may indicate that the migration of magma has utilized crustal weak zones.