Earthquake early warning across California:
Performance of ElarmS on the existing seismic networks

Richard M. Allen, Gilead Wurman, Peggy Hellweg, Alexei Kireev and Douglas Neuhauser
University of California Berkeley

AGU Fall Meeting, San Francisco, December 2007.

The ElarmS methodology is designed to provide seconds of warning prior to damaging ground shaking in earthquakes. The algorithms are currently being tested as part of a state-wide effort to assess the likely accuracy and timeliness of warnings should the system be fully implemented. This is part of a collaborative study by the California Integrated Seismic Network (CISN) and funded by the USGS. The algorithms have been running in an automated but delayed fashion since February 2006 on all earthquakes with magnitude greater than 3.0 in northern California. The processing of this data shows the sensitivity of system performance to the density of stations in the region. In the greater Bay Area where station density is greatest the system performs very well, providing accurate locations, magnitude estimates and ground shaking predictions within 2 or 3 seconds of event detection. To the north of Santa Rosa and south of Hollister the station density is lower but still sufficient for ElarmS. The lower station density means that a few additional seconds are required to obtain good predictions. The station density in the Mendocino Triple Junction region and the Sierras is not sufficient to provide useful information about earthquakes in these regions. The ElarmS development team has been porting the algorithms to the realtime system in northern California. The system is now running in a test mode 15 seconds behind realtime. We will present the performance of the realtime system and comparisons with the automated system at the meeting.

© Richard M Allen