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 understanding what represents 'normal' inter-unrest activity. In this study, we generate an earthquake catalogue for Taupō for 2010–2019 inclusive, consisting of 46,481 earthquakes. This shows that the Taupō region has background earthquake rates of 50–200 earthquakes per month and 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 and determining the presence of significant magma movement.

The Response of Taupō Volcano to the M7.8 Kaikōura Earthquake

“… (a) Cumulative number of earthquakes beneath Lake Taupō from 2012 to 2020 using earthquakes from Illsley‐Kemp et al. (2022). The Kaikōura earthquake origin time is delineated by the vertical red dashed line.…”

“…While there is no evidence for changes in seismicity at Taupō following the Kaikōura earthquake (Illsley‐Kemp et al., 2022), there was a seismic swarm a few days prior, starting on 9 November 2016 (Figure 2a), which stopped a day before the Kaikōura earthquake (Illsley‐Kemp et al., 2022). The swarm appears to have occurred on two planar east‐dipping structures in the south of the lake.…”

“…Throughout the 12-day deformation period, there were no moderate or large (>M3.0) earthquakes recorded in the region north of the lake adjacent to station 2406. Nor was there an increase in local rates of seismicity (Illsley-Kemp et al, 2022). It is possible that small earthquakes occurring near Taupōshortly after the Kaikoūra earthquake are missing from the seismicity catalog of Illsley-Kemp et al (2022), due to the high rate of largemagnitude aftershocks in the Kaikoūra region itself (Chamberlain et al, 2020(Chamberlain et al, , 2021.…”

“…Nor was there an increase in local rates of seismicity (Illsley-Kemp et al, 2022). It is possible that small earthquakes occurring near Taupōshortly after the Kaikoūra earthquake are missing from the seismicity catalog of Illsley-Kemp et al (2022), due to the high rate of largemagnitude aftershocks in the Kaikoūra region itself (Chamberlain et al, 2020(Chamberlain et al, , 2021. However, any local earthquake of a size large enough to produce the ground deformation at GNSS stations 2406, TAUP, TGHO, and TGOH is unlikely to have gone unnoticed, given that there are six seismometers within ∼20 km of GNSS station 2406.…”

“…Three days prior to the Kaikōura earthquake there was a swarm of earthquakes in the south of the lake (Figure 2). While earthquake swarms are relatively common at Taupō (Illsley‐Kemp et al., 2022), it is possible that this swarm indicates that Taupō was primed for unrest. In addition, in the 5–6 years following the Kaikōura earthquake Taupō has experienced two separate unrest events, in 2019 (Illsley‐Kemp et al., 2021) and 2022–2023 (GeoNet, 2022).…”