Tsunamis in Tasmania: Methods for understanding tsunami hazard and observations from the January 2022 Hunga Tonga-Hunga Ha’apai Tsunami
The east coast of Tasmania is directly exposed to tsunamis originating from several subduction zone regions in the South Pacific. Tasmania has experienced numerous small tsunamis in recorded history, but no records of large tsunamis exist. Numerical modelling of maximum-credible tsunami scenarios suggest that Tasmania’s east coast could experience waves of up to 7 m in amplitude, which would cause significant onshore inundation and damage to properties, infrastructure and coastal environments. In comparison, the January 2022 Hunga Tonga-Hunga Ha’apai tsunami had a maximum amplitude of 0.3-0.5 m around Tasmania, causing limited inundation of immediate foreshore areas and occasional minor damages. The tsunami was larger and arrived earlier than expected, with the warning time and regional prediction process complicated by the unusual volcanic source mechanism.
In addition to inundation models and historical observations, geological studies of tsunami evidence can add to our understanding of tsunami hazard by providing information about large, prehistoric events. Geochemical, sedimentological and microfossil studies can help distinguish tsunami deposits from storm surge or riverine flood deposits, and geophysical methods can help identify erosional tsunami signatures and map paleo-flow direction. Sedimentary evidence of large tsunamis has been studied at Bruny Island, and further work is scheduled for eastern locations that show high flow depths in the modelling studies.
Bio – Claire Kain
Claire is a Natural Hazards Geologist in the Geological Survey Branch of Mineral Resources Tasmania. She works on understanding the risk and impacts of geohazards, including landslides, earthquakes, debris flows, tsunamis and floods. Much of her work combines techniques from geomorphology, sedimentology, remote sensing and GIS, and numerical modelling. Claire is originally from New Zealand, and has worked with natural hazards and coastal processes since 2008. She completed her PhD at UNSW, focusing on the signatures of tsunamis in the landscape, before taking up her current role in 2016.