Seismic Hazards from Earthquakes in the Locked Zone Offshore Wellington

• Authors: Martha Savage, Emily Warren-Smith, Katie Jacobs, Pascal Audet, Graeme Cairns, Mladen Nedimovic, Laura Wallace, Daniel Murray & David Hobbis
• Date: 31 May 2025
• Publication Type: Report

Abstract

This project investigated the subduction interface offshore and below the Wellington region. This area is currently “locked”, building up stress that will be released in a large, destructive subduction thrust earthquake. The onshore GeoNet network is effectively blind to small earthquakes offshore, and even large earthquakes are not well located, hindering understanding of the hazard posed by the offshore subduction zone. To solve this the project deployed 20 offshore seismometers from November 2023 through early January 2025 in the locked region to detect earthquakes. Except for two stations that could not be retrieved, the data were successfully captured, and recordings of distant earthquakes from this effort are able to be used to determine the orientation of the seismometers, to relocate some earthquakes recorded by GeoNet and to find smaller earthquakes that were unable to be located by GeoNet. When the earthquakes are fully analysed, the team expect them to feed into improved seismic and tsunami hazard estimates.