Evidence of Magma Reservoirs Beneath Volcanoes in Northern Sulawesi and the Molucca Sea From Regional Earthquake Tomography

Abstract

We present a new 3-D P-wave velocity model of the crust and upper mantle beneath Sulawesi from regional earthquake body wave tomography. The arrival time data were sourced from the Agency for Meteorology, Climatology, and Geophysics (BMKG) Indonesian earthquake catalog for the period 2018 through to 2023, which is based on records from 126 seismic stations in Sulawesi and its neighborhood. Our results reveal clear evidence of high velocity subducting slabs beneath the Molucca Sea Collision Zone and northern Sulawesi, along with low velocity zones above the Sangihe and Halmahera slabs, that likely represent magma reservoirs. Furthermore, we found a diffuse low-velocity anomaly in the mantle beneath Colo volcano, a solitary island volcano located in the distant back-arc region of the North Sulawesi subduction zone, which is consistent with decompression melting induced by extension.