The relation of regional earthquakes to an intraplate volcano in the northern Hainan Island, China from magnetotelluric imaging

Abstract

Volcanic activity can cause regional earthquakes before or during an eruption, while violent earthquakes are capable of changing static and dynamic stress-fields that may consequently accelerate or trigger volcanic eruption. It is thus important to consider the volcano and regional earthquake as an integrated system, which has implications for disaster prevention and may enable early warning. In this work, two magnetotelluric (MT) profiles were deployed across the active volcanic and seismic region in the northern Hainan Island, China. Data were inverted to generate a three-dimensional resistivity structure beneath the two profiles. The resistivity model shows a shallow (< 5 km) low-resistivity (< 10 Ωm) zone corresponding to Paleogene and Neogene sediments, and two conductors (10–30 Ωm) at depths of 5–12 km. The conductors in the middle-upper crust are attributed to the accumulation of high-salinity fluids supplied by deeper magmas. The north-south trending small earthquakes (< M3) are mainly distributed in high-resistivity basement, independent of the volcanic plumbing system, which are attributed to small-scale rupture in higher tensile rocks. The volcanic plumbing system appears to extend below the Qiongzhou Earthquake (M7.5 in 1605), indicating the possibility of distal volcano-tectonic earthquake.