Characterising microseismicity in a low seismicity region: applications of short-term broadband seismic arrays in Dunedin, New Zealand

Abstract

ABSTRACT We analyse seismic data collected from a short-term array deployment in the low seismicity area of Dunedin city, New Zealand. The addition of this temporary network to the permanent GeoNet national seismic network allows detection of earthquakes not captured by the GeoNet network. Using one of the newly detected earthquakes as a master event, we employ a template match-filter analysis to identify similar events in the area. Specifically, we record a cluster of micro-events at the northern extent of the Akatore Fault (<15 km from the city centre). A recent paleoseismic study has shown the Akatore Fault to have had multiple earthquake ruptures in the late Holocene after over 110 ka of quiescence, so the observed microseismicity is consistent with the fault being in a state of elevated activity. In contrast, other known faults in the area are quiescent with respect to both microseismicity and Holocene ruptures. The establishment of a permanent seismic array in and around Dunedin for the monitoring of microseismicity on the Akatore Fault and other local faults is warranted.