CISN ShakeAlert: Decision Module Enhancements for Earthquake Alerts

The California Integrated Seismic Network (CISN) has been developing CISN ShakeAlert, a prototype end-to-end earthquake early warning system, for the purpose of testing earthquake alerts with a small group of users in California. Rather than adopting a single methodology, the CISN is building a system that can accept event detections, magnitude estimates, and ground shaking predictions and observations from several Detection Modules that use independent algorithms and methodologies. The Decision Module is the ShakeAlert component that receives earthquake detections and hazard assessments from multiple independent Detection Modules, aggregates and correlates this information, and provides a single evolving view of the earthquake in progress to be delivered as an alert to people in harm's way. The alert messages generated by the Decision Module include the best or average estimate of earthquake magnitude and location, and can include predicted peak ground motion. As additional information is received from the Detection Modules, the Decision Module updates its view of the event and its assessment of the reliability of the prediction, and continues to distribute updated alert messages. The Decision Module publishes all of its alerts to a subscription-based messaging system, allowing end-user applications to utilize the earthquake alerts generated by ShakeAlert for their specific use and to make decisions based on the reliability estimates from ShakeAlert. Recent enhancements to the system include a reduction of data latencies with smaller transmission packets, improved alert times, SSL encryption of alert messages, and the integration of current peak value streams into the messaging system which publishes these observation values with earthquake alerts, allowing end-user applications to utilize the additional information about the ongoing earthquake.