Tectonic tremor and microseismicity associated with shallow slow slip along the northern Hikurangi Margin, New Zealand

Abstract:

The detection of circum-Pacific slow slip events (SSEs) along with associated tectonic tremor and microseismicity has led to numerous investigations into the modes and timescales of deformation in subduction zone boundaries. This discovery has shed light on a broader range of strain release processes that range from aseismic creep at plate convergence rates (cm/yr) to traditional earthquake slip rates (m/s). The largest SSEs along the northern Hikurangi subduction margin occur offshore Gisborne, New Zealand every 18-24 months at depths less than 15 km. We present a systematic investigation of tremor and microseismicity associated with these shallow SSEs from 2010 to the present using land data from the New Zealand National Seismograph Network operated by GeoNet (http://geonet.org.nz) and ocean-bottom data from the Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip (HOBITSS) project. The HOBITSS project deployed an array of ocean-bottom seismometers and absolute pressure gauges between May 2014 and June 2015 above the Gisborne SSE patch. These instruments were in place during a large SSE in September/October 2014. Tremor and seismicity associated with Gisborne SSEs primarily occur along the downdip edge of the slip patch, but the addition of data from ocean-bottom stations located directly above the slip patch will reveal the updip extent of tremor and microseismicity related to these SSEs.