Increase in magma supply to Sakurajima volcano’s (Japan) shallow magma chamber over the past 500 years

Abstract

Constraining the magma supply to a subvolcanic reservoir is crucial to characterizing unrest and evaluating the potential for a forthcoming eruption. With the advent of GPS, tiltmeters, and satellite interferometry, it has been possible to infer changes in the supply rate of magma to shallow reservoirs over time scales of as much as decades. While these methods have impacted our ability to characterize volcanic unrest, they only probe magmatic activity over short time scales. Here, we constrain changes in magma supply rate at Sakurajima volcano (Kyushu, Japan) over the past five centuries. The combination of thermo-mechanical modeling, documented eruption history, and textural analyses of pumices allows us to tightly constrain the long-term rate of magma supply to the subvolcanic chamber through time. Specifically, we find that magma supply rate has increased by roughly an order of magnitude over the past 500 years and that the bubble content in the magma chamber has increased over time, explaining the changes in eruption volume between the Bunmei (ca. A.D. 1470), An-ei (ca. A.D. 1780), and Taisho (A.D. 1914) eruptions.