CISN ShakeAlert: Prototype User Display for Providing Earthquake Alerts to End Users

Over the past five years scientists from Caltech, UC Berkeley, ETH Zurich, USC/SCEC and USGS have been working on the development and implementation of a prototype earthquake early warning system for California. CISN ShakeAlert combines the outputs from three independently running algorithms, Tauc-Pd Onsite, Virtual Seismologist, and ElarmS. CISN ShakeAlert provides a continuum of earthquake alert information, including rapid estimates of magnitudes, locations, and expected seismic intensities and their uncertainties. For the rapid visualization of alert information and the notification of users in an easy understandable way, we have developed a Java applet that runs on a user computer and receives xml messages from the ShakeAlert system. This UserDisplay (UD) shows the user location, estimated epicenter of the earthquake, current locations of the P- and S-wave fronts, estimated magnitude, as well as the predicted level of intensity of shaking at the user site and time until this shaking is expected to occur. The UD pops up automatically once an alert message is received. Users can specify thresholds for magnitudes and intensities to reduce the number of alerts. Xml messages received by the UD are locally stored on the user computer and can be replayed. To ensure robust communication, the UD receives and displays heartbeats coming from the three algorithms and the DecisionModule of the ShakeAlert system. The UD is currently being tested by approximately 30 test users.