Revised Geometry for the Hikurangi Subduction Thrust, New Zealand: Application to Slow Slip Event Inversions and Hydrological Modeling on the Hikurangi Subduction Interface
Abstract
Slow slip events (SSEs) occur along nearly the entire Hikurangi subduction margin adjacent to the North Island, New Zealand. Long duration, deep, large events occur at the southern Hikurangi margin, while short duration, shallow, smaller events occur at the northern and central Hikurangi margin. We are attempting to understand the factors controlling the distribution of these SSEs by 1) Providing a more accurate description of the interface geometry; 2) Including the effects of material heterogeneity in our geodetic inversions of slow slip; and 3) Examining the effects of pore fluid pressure on frictional fault behavior. Accurate knowledge of interface geometry is critical in both forward and inverse models of SSEs. To address this, we have combined recent seismic reflection results and trench bathymetry with seismicity results to provide a parametric representation of the Hikurangi interface. Using this merged geometric model, we then make use of a New Zealand-wide 3D seismic velocity model and the finite element code PyLith to generate Green's functions that are used to perform inversions for slow slip distributions constrained by GPS observations. The improved geometry in combination with the inclusion of material heterogeneity should provide much more accurate predictions of the slip distributions. Finally, we examine the effects of pore fluid pressure on fault frictional behavior by examining a 2D seismic reflection profile near Gisborne. This profile captures a subducting seamount, as well as a region of SSE activity downdip of the seamount. Using geometric and material property constraints provided by the seismic reflection data, we use the finite element code SUTRA to model the fluid flow for this region. We then use PyLith to model the frictional interface, using the predicted pore fluid pressures from SUTRA to modify the initial effective normal stress on the fault. By combining the fluid flow model with a frictional fault model, we hope to gain a better understanding of the factors controlling SSE occurrence along the Hikurangi subduction margin.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.S33B2532W
- Keywords:
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- 0545 COMPUTATIONAL GEOPHYSICS / Modeling;
- 1207 GEODESY AND GRAVITY / Transient deformation;
- 7240 SEISMOLOGY / Subduction zones