Earthquake Early Warning Scenarios for Alaska

ABSTRACT Alaska presents several challenges for earthquake early warning (EEW) systems. These include the presence of offshore earthquakes, transform boundaries, and crustal faults extending hundreds of kilometers, deep earthquakes, and a complicated coastline. This variety, combined with population centers spread far apart, makes it challenging to anticipate early warning performance and design systems accordingly. As Alaska begins to plan for early warning, we present here a set of scenarios intended to inform these activities. Our objective is to envision how, and how well, early warning will function in Alaska. We present warning time estimates for groups of deterministic earthquake scenarios along known faults. These scenarios demonstrate how changes in source characteristics, such as magnitude, depth, location, and fault style, impact the timeliness of warnings and associated ground motions. We combine source time models and travel times for the current seismic network to model detection and alert times. We compare the resulting warning times and peak ground motions to determine the warning effectiveness. Our results demonstrate that even the current network geometry is theoretically capable of providing 0–20 s of warning for intensity 6 for many shallow crustal earthquakes. Increasing the station density can add another 5–15 s to these warning times and provide positive warning times for shaking of intensity 8. Deep and offshore earthquakes benefit less directly from increased station density. For these earthquakes, it is theoretically possible to provide positive warning times for most shaking of intensity 8. Informed by these results, we discuss where we expect an EEW system to excel and what challenges should be tackled to improve other areas.