Earthquake Early Warning Testing Developments: Realistic Warning Time Estimates for Large Magnitude Events

Abstract:

Earthquake early warning (EEW) algorithms must undergo rigorous real-time and offline testing before being accepted into the ShakeAlert production system. The ShakeAlert Testing and Certification platform attempts to simulate how the production system will perform by deploying the proposed algorithms, configurations, earthworm rings/modules, and ActiveMQ messaging on separate, nearly identical hardware. For real-time testing, the test servers are fed the same West Coast input waveform data as the production servers, and the algorithms’ performance is compared between the test and existing production systems after a minimum of two weeks. For offline testing, four simultaneous instances of the algorithms are run on one machine with a historic test suite of earthworm tankplayer files (a format used for replaying data into an earthworm ring with realistic timing).

One important development of the test system that is underway, is generating realistic estimates of EEW warning times. We have already gathered many large magnitude events for the new test suite, including crustal and subduction zone events from Japan, events from Ridgecrest, Anchorage, and older events; therefore, a next step is to use some of these events to help estimate warning times that the ShakeAlert system might generate for different MMI levels. We currently have a program that can be applied to the large magnitude events to calculate MMI as a function of time directly from the waveform data and are developing an accompanying program that interpolates these estimates onto a regular grid. In addition, we are working with playbacks that incorporate realistic latencies and realistic packet timing using the earthworm ringplayer program. Last, we are working on techniques to automatically visualize and analyze the test results in terms of ground motion space to help us quickly assess the performance and warning times.