Solving the enigma of Tsunami Earthquakes – the underrated hazard

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, which will provide our team with unprecedented constraints on the physical environment of Tsunami earthquakes. Our proposed work will determine which physical processes best explain our global observations regarding Tsunami earthquake occurrence by underpinning analytical models with well-resolved plate boundary properties. Establishing this link will greatly improve assessments of Tsunami earthquake hazard globally.