Using seismology to probe the modern magma reservoir at Taupō volcano, Aotearoa New Zealand

Abstract

<p>Taupō volcano, in the centre of North Island, Aotearoa New Zealand, is a frequently active rhyolitic caldera volcano that was the site of Earth’s most recent supereruption (Oruanui ~25 ka)<sup>1,2</sup>. It has erupted 28 times since then, and continues to display signs of unrest (seismicity and surface deformation), with periods of elevated unrest on roughly decadal timescales<sup>3</sup>. Any resumption of eruptive activity at the volcano poses a major source of hazard, and interactions between the magma reservoir and the regional tectonics that lead to unrest and possible eruption are not well understood. The location of the modern magma reservoir has been previously constrained by study of past eruptive products and some geophysical imaging (gravity, broad-scale tomography)<sup>2</sup>. Earthquake patterns during a 2019 unrest episode have also been used to infer the location and size (>~250 km<sup>3</sup>) of the modern-day reservoir<sup>4</sup>, but its location and extent have not yet been directly imaged. As part of the interdisciplinary ECLIPSE project, seismological methods are being used to investigate the Taupō reservoir, combining data from the national GeoNet seismic network with records from a temporary 13 broadband seismometer network. Development of the ECLIPSE network approximately doubles the number of seismic stations within 10 km of the lake shore.</p><p>We present here initial results on the characterisation of the seismicity in the Taupō region. These results include the improvement of earthquake locations with the addition of picks from the ECLIPSE stations and the use of automated machine learning phase picking and association techniques. We also present initial results from the cross correlation of ambient noise between stations in the ECLIPSE network for the use in ambient noise surface wave tomography, with many of the station pairs crossing the region most likely to contain the modern-day magma reservoir.</p><p><sup>1</sup> Wilson CJN J. Volcanol Geotherm Res 112, 133 (2001) <br><sup>2</sup> Barker SJ et al. NZ J Geol Geophys 64, 320 (2021) <br><sup>3</sup> Potter SH et al. Bull Volcanol 77, 78 (2015) <br><sup>4</sup> Illsley‐Kemp F et al. G-cubed 22, e2021GC009803 (2021)</p>