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Modeling the Seismogenic Slab Sources in New Zealand

Description: 

Intraslab earthquakes within the Hikurangi and Puysegur subduction zones constitute more than 50% of the recorded (MW≥4.0 events) seismicity in New Zealand. As part of the National Seismic Hazard Model 2022, we develop an advanced source model for the intraslab seismicity, using recently improved datasets that include an earthquake catalog, geospatial configurations of the subduction interfaces, and a regional moment tensor solution catalog. To obtain the smooth seismicity distributions, we apply a novel quasi-3D approach. The steps are as follows: (1) delineate the mid-slab based on the hypocentral locations, (2) get the orthogonal projections of hypocenters onto the mid-slab, (3) generate a uniform grid of 0.1 degrees on the mid-slab, and (4) finally, apply a Gaussian smoothing kernel. For each slab, we compute the magnitude frequency distributions. At the same time, we consider the maximum magnitude to range M_W 8.0 – 8.3, based on globally-observed historical intraslab earthquakes. To account for finite-fault ruptures, we construct a model for rupture mechanisms, by analyzing the moment tensor solution catalog. This model has the mean strike angles sub-parallel to subduction trenches and median dip angles ≥ 60°. The distribution of rake angles suggests that the Hikurangi slab has an extensional regime in the shallower parts but a compressional regime in the deeper parts, indicative of slab flexural. In contrast, the Puysegur slab predominantly exhibits a compressional regime.

Session: Opportunities and Challenges in Source Modeling for Seismic Hazard Analysis [Poster]

Type: Poster

Date: 4/20/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Kiran Kumar S. Thingbaijam

Student Presenter: No

Invited Presentation: 

Authors