TY  - JOUR
A1  - Bannister, Stephen
A1  - Bertrand, Edward A.
A1  - Heimann, Sebastian
A1  - Bourguignon, Sandra
A1  - Asher, Cameron
A1  - Shanks, Jackson
A1  - Harvison, Adrian
T1  - Imaging sub-caldera structure with local seismicity, Okataina Volcanic Centre, Taupo Volcanic Zone, using double-difference seismic tomography
JF  - Journal of volcanology and geothermal research
N2  - We examine sub-caldera structure and seismicity in and around the Okataina Volcanic Centre (OVC), Taupo Volcanic Zone, New Zealand, using seismic data collected over 4+ years with a temporary array of broadband and short-period seismometers, supplementing data from the permanent New Zealand seismometer network. 

We derive a new 3-D image of P-wave seismic velocity for the upper crust in the region, using double-difference seismic tomography and utilising waveform cross-correlations. We subsequently relocate 6989 earthquakes which occurred in the region over the 2010-2021 time period, using the 3D velocity model. 
The seismicity distribution shows spatial clusters west of Lake Rotomahana, as well as beneath Haroharo and the Makatiti Dome, inside the Okataina caldera. Beneath Makatiti Dome 90% of the events are shallower than 7.7 +/- 0.5 km. 

Outside of the Okataina caldera event relocations highlight short (similar to 3-4 km long) streaks of activity in the Ngakuru graben, part of the active Taupo Rift southwest of Okataina caldera. Inside the OVC the relocated seismicity beneath Makatiti appears closely associated with low (similar to 10%) P-wave velocity anomalies, which we resolve in the similar to 5-to-8-km depth range beneath the Okataina caldera, and which are likely related to partial melt and/or fluid-volatile pathways. 
Moment tensor analyses for two larger-magnitude events (M(L)4.5 and M(L)4.9) near Haroharo indicate normal faulting, with NNE-SSW fault strike, but with positive CLVD and positive isotropic components when allowing for a full moment tensor, consistent with a magmatic environment with degassing and/or fluid migration.
KW  - Okataina Caldera
KW  - Taupo Rift
KW  - seismic tomography
KW  - sub-caldera structure
KW  - Volcanic system
Y1  - 2022
U6  - https://doi.org/10.1016/j.jvolgeores.2022.107653
SN  - 0377-0273
SN  - 1872-6097
VL  - 431
PB  - Elsevier
CY  - Amsterdam
ER  -