CISN ShakeAlert: ElarmS

ElarmS is a network-based earthquake early warning (EEW) algorithm developed at UC Berkeley for rapid earthquake detection, location and hazard assessment. ElarmS operates as part of the greater ShakeAlert EEW system, an ongoing project by the California Integrated Seismic Network (CISN) (see other abstracts in this session). ElarmS consists of two primary parts: (1) a waveform processing algorithm, which runs in parallel at UC Berkeley, Caltech, and USGS Menlo Park to continuously filter real time seismic data, and (2) a single state-wide event detection algorithm which operates at UC Berkeley. The event detection module analyzes the incoming data from the three waveform processing streams and identifies earthquakes in progress. ElarmS then sends alert messages to the CISN ShakeAlert Decision Module. In 2010 and 2011 we developed second generation ElarmS waveform processing and event detection algorithms, based in C++ for speed and adaptability. The new event detection module (E2) utilizes the established location and magnitude relations, but has an updated method of associating triggers together to form events. E2 has been processing real-time data in test mode since December 2010 and will become the authoritative ElarmS version in fall 2011. In 2011 we also began investigating the use of GPS for earthquake early warning, focusing on the Mw 7.2 El Mayor-Cucapah earthquake, which had both real-time GPS and seismic data available. Initial results suggest that GPS would provide a valuable contribution to EEW. The new approach provides an independent estimate of magnitude, which is particularly important for the largest events.