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The Potential Contribution of Real-Time Distributed Slip Models to Subduction Zone Earthquake Early Warning in the Context of Ground Motion Thresholds and Alerting Strategy

Description: 

Earthquake early warning systems like ShakeAlert estimate source parameters (e.g., Mw and location) in order to calculate anticipated shaking. Users receive alerts where forecast ground motion (GMpred) exceeds a pre-set alert threshold, tA. Alert timeliness can improve if tA < tT, the target shaking level for which we hope to alert users (Minson et al., Sci. Adv. 2018). ShakeAlert uses two seismic algorithms that estimate parameters of a point or line source representing the earthquake. Large (e.g., M8.0+) subduction interface earthquakes’ offshore location, magnitude, and rupture extent are a challenge to accurate real-time source characterization. This work evaluates if the BEFORES algorithm (Minson et al., JGR, 2014), which infers temporally-evolving, three-dimensional distributed slip models (DSMs) from real-time global navigation satellite system data, can improve performance. Previously (Murray, AGU Fall Mtg. 2023, NH13C-0690), I compared alert outcomes using BEFORES’ DSMs to those from published post-event DSMs and point source models (“best case” parameter estimates) as well as models from ShakeAlert’s existing algorithms. Outcomes were quantified by correct, missed, and over alerts relative to ShakeMaps (GMobs) using tA = MMI 4 and tT = MMI 6. For two events it was also possible to evaluate alert timeliness. Most source models had similar correct alert performance to ShakeMap for the chosen thresholds, even when GMobs and GMpred differed by >1 MMI unit. These thresholds led to over alerts (GMpred > tA, GMobs < tT) for large areas, even for the ShakeMaps. BEFORES caused larger over alert areas than retrospective DSMs but did not increase the total over alert area compared to ShakeMap for the earthquakes and thresholds tested. BEFORES showed potential to improve timeliness and reduce missed alerts. Here I present follow-on work suggesting BEFORES may improve alerting for higher tA (e.g., an MMI 5 “take action” threshold), and I consider BEFORES’ contribution in the context of unilateral subduction interface ruptures and preemptive alerting of a large region if the Mw estimate exceeds a certain value.

Session: End-to-End Advancements in Earthquake Early Warning Systems -IV

Type: Oral

Date: 5/3/2024

Presentation Time: 10:45 AM (local time)

Presenting Author: Jessica

Student Presenter: No

Invited Presentation: 

Authors