A decade of earthquake activity at Taupō Volcano, New Zealand

Abstract

Taupō, New Zealand, is an active caldera volcano that in recent times has erupted on average every ∼500 years, with the latest explosive eruption in 232±10 CE. Monitoring at Taupō is challenging as there has been no eruptive activity in documented history; however Taupō does undergo periods of unrest on roughly a decadal timescale, such as in 2019. Key to identifying these unrest periods is the establishment of what represents ‘normal’ inter-unrest activity. In this study, we generate and present a detailed earthquake catalogue for Taupō for 2010–2019 inclusive, consisting of 46,481 earthquakes. This record shows that the Taupō region has background earthquake rates of 50–200 earthquakes per month and that the 2019 unrest episode was preceded by an exponential increase in earthquake rate. We also show that when attenuation is accounted for there is no evidence for low-frequency earthquakes at Taupō, and that this is an important consideration for volcano monitoring as low-frequency earthquakes are often used to determine magma movement.