The Theoretical and Observational Limits of Earthquake Early Warning

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Sarah Minson

USGS Menlo Park

Date & Time
Building 3, Rambo Auditorium

The goal of earthquake warning is ground-motion early warning: to predict expected ground shaking intensity so that action can be taken at various locations to prepare for the imminent ground motion. The usefulness of early warning depends both on the accuracy of the ground motion prediction and the timeliness of the warning. (We take timeliness to be the time difference between when the warning is received and when the expected ground motion arrives at the user's location, minus the time needed for users to take precautionary measures.) The time required to issue a warning depends on several factors including the telemetry latency associated with receiving real-time data, the computational time needed to analyze those data, and, most crucially, the time needed to characterize the earthquake source in order to make accurate ground motion predictions. In this study we explore, both theoretically and observationally, the conditions necessary to make an accurate ground motion prediction and the temporal evolution of the expected accuracy of early-warning systems. We consider the limits of rapid magnitude estimation given the non-deterministic nature of earthquake rupture and the band-limited, Gaussian white noise properties of high-frequency (i.e., PGA) ground motion. We also study the best-case warning time scenario given the limits on magnitude estimation and the finiteness of large faults. Finally, we consider the accuracy and effectiveness of real-time ground-motion prediction given the uncertainties and limitations in magnitude estimation and the range of potential warning times.

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