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This project seeks to understand what plate boundary properties promote their occurrence and where Tsunami earthquakes pose a significant but potentially underrated hazard to coastal populations.
Tsunami earthquakes are shallow, long-duration earthquakes at subduction zones that generate disproportionately large tsunami relative to earthquake magnitude. Such earthquakes pose a large hazard to coastal populations, as the ground shaking is typically not sufficient to prompt self-evacuation prior to the arrival of the tsunami.
A major unknown in global hazard models is whether the risk of Tsunami earthquakes is prevalent across all subduction zones or is only locally heightened by unique physical characteristics. We have identified a global paradox whereby the topography overlying Tsunami earthquake zones is steeper than would be expected if the subduction fault is weak, as minimal ground shaking would suggest. We will test contrasting physical interpretations of this paradox by integrating new electromagnetic data with cutting-edge processing of marine seismic data along New Zealand’s Hikurangi margin. This is the first time these complementary datasets have been available for any subduction zone and will provide our team with unprecedented constraints on the physical environment of Tsunami earthquakes.
Tsunami earthquakes are fault ruptures that are fast enough to generate a tsunami, but slow enough to limit the production of seismic energy needed to trigger tsunami warning systems or prompt self-evacuation. They occupy a poorly understood middle ground, and present an underrated hazard, especially for New Zealand communities schooled to use the civil defence rule-of-thumb Long or strong, get gone.
The Hikurangi plate boundary, located off the East Coast of the North Island, is where the Pacific tectonic plate subducts the Australian tectonic plate.
The Hikurangi Project is a multinational science investigation of the subduction zone beneath New Zealand's North Island.
There are some 51,000 kilometres of subduction plate boundary on Earth. So far, only 3% of this length has demonstrated the capacity for generating tsunami earthquakes. However, an additional 15% shows a similar structure to known tsunami earthquake zones.
The project, led by GNS Science, will bring together international researchers in several geoscience specialties. They aim to better understand the physical processes that predispose areas of subduction zones to the occurrence of tsunami earthquakes.
The tsunami earthquake project is focused on the Hikurangi subduction zone – known to be potentially New Zealand’s largest source of geohazards – where the Pacific Plate descends beneath the North Island, just off the East Coast. Two Tsunami earthquakes were generated in 1947 from locations offshore Tolaga and Poverty Bay.
Chesley, C., Naif, S., Key, K., & Bassett, D. (2021). Fluid-rich subducting topography generates anomalous forearc porosity. Nature, 595(7866), 255-260.
Dan is a Marine Geophysicist with broad interests in the structure, dynamics and slip-behaviour of subduction zones. Dans primary interest lies in using marine geophysical methods to produce detailed images of the Earth’s crust. I integrate these models with geologic, earthquake and geodetic data to investigate the physical mechanisms that control fault slip behaviour.
View Bio Contact MeCollaborators: University of Texas at Austin, Georgia Tech, Lamont Doherty Earth Observatory
2020–2023
Marsden Fund
Current
Dan Bassett, GNS Science
Marsden Fund