Breakthrough underwater technology holds promise for improved local tsunami warnings

Recent advances in deep-ocean tsunami measurement technology coupled with tsunami forecast models have demonstrated that tsunami impact can be predicted before the tsunami reaches the affected coastlines. Since 2004, tsunami impacts have been predicted for 33 tsunamis detected in the deep-ocean with about 80% accuracy when observations and predictions at tide gauges are compared. In most of these tsunamis, the forecast was based on observations typically 1000km or more from the earthquake epicenter. A remaining challenge is to forecast tsunamis in the near field where the tsunami signal may be overwhelmed by the earthquake vibrations. A new generation of pressure sensors, named nano-resolution pressure sensors, can provide high temporal resolution of the earthquake and tsunami signals without losing precision. The nano-resolution pressure sensor offers a state-of-the-science ability to separate earthquake vibrations and other oceanic noise from tsunami waveforms, paving the way for accurate, early warnings of local tsunamis. This study describes an experiment, begun on June 30, 2010 at the Monterey Accelerated Research System (MARS) cabled observatory in Monterey, California, comparing conventional pressure sensors with the nano-resolution sensor at a depth of approximately 900m. The study will include examples of earthquakes, both local and remote, detected by the nano-resolution pressure sensor since its deployment. Wavelet analysis has been employed to identify two remote micro-tsunamis in late 2010. The events (Dec. 21, M7.4 at Bonin Island; Dec. 25, M7.3 near Vanuatu) produced tsunami signals of 1-2 mm in amplitude in Monterey Bay at periods near 14 minutes.