Observation of the 2009 Samoa tsunami by the NEPTUNE-Canada cabled observatory: Test data for an operational regional tsunami forecast model

Abstract

[1] As part of the NEPTUNE-Canada cabled seafloor observatory, an array of six high-precision bottom pressure recorders was installed in the late summer of 2009 at depths from 100 to 2600 m seaward of the southwest coast of Vancouver Island in the northeast Pacific. The instruments transmit 1-sec bottom pressure data at roughly 0.1 mm equivalent sea level height to the Data Management and Archiving System (DMAS) at the University of Victoria. On September 30, 2009, the array recorded waves of 2.5 to 6 cm amplitude associated with the transoceanic tsunami generated by the Mw = 8.1 Samoa earthquake in the South Pacific. These open-ocean observations were uncontaminated by coastal effects, demonstrating that NEPTUNE records from future tsunami events can be effectively used as realtime input to a regional numerical tsunami forecast model. We validate this proposition by showing that wave forms simulated by the regional model using the leading train of waves of the 2009 event are in good agreement with observed tsunami records for both the shelf stations and nearby coastal tide gauges. Tsunami waves simulated by this model are also significantly more accurate for local regions than those determined by global-scale tsunami models. This ability to assimilate “pristine” open-ocean data from the cabled observatory into an operational tsunami forecast model makes it possible to provide updated wave information that could help mitigate the impact of future tsunamis approaching the west coast of British Columbia and northern Washington State.