Initial Results from the Enhanced Seismometer Network Around Taupō Volcano, North Island, New Zealand.

Abstract:

Taupō volcano, site of Earth’s most recent supereruption (Oruanui ~25.5 ka), has erupted 28 times since then and continues to display signs of unrest. However, little is known about the modern-day magma reservoir, and interactions between the magma system and its tectonic rift setting are poorly constrained. The presence of Lake Taupō means that most previous crustal-scale geophysical studies have not covered the volcano. The Lake Taupō area was particularly seismically active in 2019, with around 1000 shallow (<25 km depth) earthquakes detected and located by GeoNet under the lake, including the largest earthquake in the area for at least 60 years (M = 5.2). The locations of many of the earthquakes were associated with volcanic structures, such as the Oruanui structural caldera and younger vent sites. Unrest on this scale appears to repeat on approximately a decadal timescale.

To investigate the distribution of seismicity in the area and the crustal structure beneath Taupō, we are deploying a new network of 13 broadband seismometers, taking a co-production approach working with the local Iwi: Ngāti Tūwharetoa. The network (ECLIPSE) is designed to complement the existing GeoNet network and significantly increases the number of seismic sites within 20 km of the volcano.

Data from the new ECLIPSE network will be used to image the crust to identify the location, geometry and state of the modern-day magma reservoir, and to characterise the seismicity in detail to determine what is controlling its present distribution. Initial results from 8 stations indicate that S-wave energy is attenuated most for ray paths that pass through the crust under the Oruanui caldera area, and that many earthquakes are deeper than the operator-assigned 5km GeoNet depths.