Investigation of Phase-Converted Seismic Waves at the Hikurangi Plate Interface, New Zealand
Journal Article
Overview
abstract
In the northern Hikurangi margin, aseismic slip events known as slow; slip events (SSEs) occur approximately every 18-24 months with a long; duration (weeks to months), and have been shown to cause 1 to 3 cm of; horizontal surface displacement onshore and 1.5 to 5.4 cm of vertical; displacement (uplift) offshore. The discovery of SSEs has expanded our; scientific understanding of slip behavior at subduction zones to; encompass behaviors beyond earthquake-producing (fast) slip events.; Using converted phase seismic signals from local earthquakes in addition; to direct P and S arrivals allows us to further analyze the properties; of the plate interface along the subduction zone, including its; composition, Âtopography and heterogeneity. It has been hypothesized; that these properties play a role in the process of slow slip, therefore; our investigation of converted waves focuses on the area offshore the; east coast of the North Island of New Zealand, where dozens of SSEs have; been observed in the past twenty years. We examine an earthquake catalog; comprised of local slab earthquakes occurring recorded on ocean-bottom; seismometers (OBSs) from the one-year-long Hikurangi Ocean Bottom; Investigation of Tremor and Slow Slip (HOBITSS) experiment as well as; New Zealand’s permanent GeoNet on-land seismic network. Preliminary; findings indicate strong secondary arrivals on the vertical component of; the land stations which are likely Sp conversions from the plate; interface. We aim to identify conversions from the plate interface on; the OBSs from the HOBITSS experiment, as these data will help us resolve; a part of the plate interface that was not investigated in previous; converted wave studies. We will conduct a systematic search for; phase-converted arrivals from the plate interface, initially focusing; primarily on Sp conversions by examining the vertical component; seismograms.
