U.S. Tsunami Information technology (TIM) Modernization: Performance Assessment of Tsunamigenic Earthquake Discrimination System

Abstract:

Tsunami warning centers must rapidly decide whether an earthquake is likely to generate a destructive tsunami in order to issue a tsunami warning quickly after a large event. For very large events (Mw > 8 or so), magnitude and location alone are sufficient to warrant an alert. However, for events of smaller magnitude (e.g., Mw ~ 7.5), particularly for so-called "tsunami earthquakes", magnitude alone is insufficient to issue an alert and other measurements must be rapidly made and used to assess tsunamigenic potential.

The Tsunami Information technology Modernization (TIM) is a National Oceanic and Atmospheric Administration (NOAA) project to update and standardize the earthquake and tsunami monitoring systems currently employed at the U.S. Tsunami Warning Centers in Ewa Beach, Hawaii (PTWC) and Palmer, Alaska (NTWC). We (ISTI) are responsible for implementing the seismic monitoring components in this new system, including real-time seismic data collection and seismic processing. The seismic data processor includes a variety of methods aimed at real-time discrimination of tsunamigenic events, including: Mwp, Me, slowness (Theta), W-phase, mantle magnitude (Mm), array processing and finite-fault inversion. In addition, it contains the ability to designate earthquake scenarios and play the resulting synthetic seismograms through the processing system. Thus, it is also a convenient tool that integrates research and monitoring and may be used to calibrate and tune the real-time monitoring system.

Here we show results of the automated processing system for a large dataset of subduction zone earthquakes containing recent tsunami earthquakes and we examine the accuracy of the various discrimation methods and discuss issues related to their successful real-time application.