Evaluating earthquake early warning performance using "Did You Feel It?"

Jessie K. Saunders, & David J. Wald

Submitted September 7, 2025, SCEC Contribution #14517, 2025 SCEC Annual Meeting Poster #TBD

We examine responses to the U.S. Geological Survey’s “Did You Feel It?” (DYFI) survey and its companion earthquake early warning (EEW) questionnaire to assess the performance of the U.S. ShakeAlert EEW system directly from the alert recipients’ perspectives. ShakeAlert rapidly detects earthquakes and develops alert information, but as official alert delivery partners issue these alerts, it is difficult to determine how many people were alerted and when. We investigate DYFI reports for six California earthquakes that had EEW alerts and substantial responses to the DYFI EEW questionnaire. Comparisons of ShakeAlert predictions to reported intensities demonstrate that magnitude estimation accuracy is not necessarily indicative of ground‐motion prediction accuracy. Perceived warning time distributions from DYFI indicate that estimating maximum‐expected warning times using the S‐wave arrival is reasonable for discussing public EEW performance. However, we also find many reports of shorter warning times, late alerts, and missed alerts than expected based on ShakeAlert publication times, indicating alert delivery latencies are substantial and highly variable. The novelty of our analysis is that we demonstrate that the DYFI EEW survey provides useful EEW efficacy information, independent of the specific alerting pathway, that can be used to inform our choices for conveying EEW performance.

Key Words
Did You Feel It, earthquake early warning

Citation
Saunders, J. K., & Wald, D. J. (2025, 09). Evaluating earthquake early warning performance using "Did You Feel It?". Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology