Development of a slow slip catalog for the Hikurangi subduction margin, New Zealand

Charles A. Williams, Laura M. Wallace, Noel M. Bartlow, & John Haines

Published August 1, 2019, SCEC Contribution #9321, 2019 SCEC Annual Meeting Poster #203

Slow slip events (SSEs) occur frequently along the Hikurangi Margin in New Zealand, and understanding these events is critical to our understanding of interseismic coupling, plate motion budgets, and the potential for damaging earthquakes. Along the Hikurangi, deeper and less frequent SSEs with longer durations are observed along the southern part of the margin, while shallower and more frequent events with shorter durations are observed along the northern section. We have started to put together a catalog of Hikurangi SSEs covering the time period from 2006 to 2016 to help us understand the spatial and temporal patterns of slip along the Hikurangi Margin.

We use the Network Inversion Filter (NIF) [Segall and Matthews,1997; McGuire and Segall, 2003; Miyazaki et al.,2006] to perform our time-dependent slip inversions. We generate the Green’s functions for our inversions using the PyLith finite element code [Aagaard et al., 2013] to allow consideration of elastic property variations provided by the New Zealand-wide seismic velocity model [Eberhart-Phillips et al., 2010]. Previous results [Williams and Wallace, 2015; 2018] have shown that SSE inversions that consider elastic heterogeneity provide significantly different results than inversions based on elastic half-space solutions. Incorporating these effects should significantly improve the accuracy and reliability of our time-dependent inversions. Our inversions also include absolute pressure gauge (APG) data to constrain offshore vertical movement during a recent SSE observed in 2014. The catalog we are developing will represent the most comprehensive to date for the Hikurangi Margin, and the usage of APG data and consideration of elastic heterogeneity effects will provide the best possible constraints on the predicted slip distributions.

Key Words
Slow slip, geodetic inversion, subduction, numerical modeling

Citation
Williams, C. A., Wallace, L. M., Bartlow, N. M., & Haines, J. (2019, 08). Development of a slow slip catalog for the Hikurangi subduction margin, New Zealand. Poster Presentation at 2019 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy