ElarmS Earthquake Early Warning System Enhancements and Performance Evaluation

ElarmS is an earthquake early warning system that contributes alerts to CISN ShakeAlert, a prototype end-to-end earthquake early warning system being developed and tested by the California Integrated Seismic Network (CISN). ElarmS is one of several systems based on independent methodologies that contribute to CISN ShakeAlert. The UC Berkeley ElarmS system consists of multiple continuous-waveform processors and trigger-association processors running at three geographical locations and communicating via the Apache ActiveMQ Messaging system. Recent enhancements to the ElarmS system include reductions in trigger report times, reductions in trigger association and event alert times, and the development and testing of redundant processing and communication architectures. To enable redundant processing, ElarmS trigger associators handle duplicate trigger information arriving from duplicate waveform processors via different transmission paths. We have developed performance monitoring tools that report system component latencies and earthquake hypocenter parameter accuracy. Statistics for hypocenter and origin time accuracy and alert times latencies can be computed for different time periods, magnitude ranges and geographic regions. Individual earthquake processing histories can be examined, including details of the transmission and processing latencies associated with individual P-wave triggers, from arrival detection through several stages of processing to the association with an individual earthquake alert. Detailed event information includes latencies associated with the transmission of individual waveform packets from station to processing centers, waveform processing queues, trigger message queues, trigger message transmissions, trigger association and hypocenter location cpu times. Changes to the ElarmS algorithm and system architecture are frequently tested by running multiple versions of ElarmS simultaneously. A web browser interface to the performance monitoring tools includes tabular, mapping, and statistical analysis graphical components (generated by the R-Statistics System) that make it easy to compare different development versions of ElarmS.