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Assessing the Hazard of Highly Clustered M~5 Caldera Collapse Earthquakes in Kīlauea Volcano, Hawai‘i

Session: Beyond Poisson: Seismic Hazards and Risk Assessment for the Real Earth [Poster]

Type: Poster

Date: 4/19/2021

Presentation Time: 11:30 AM Pacific

Description: 

The complicated volcanic and tectonic processes in Hawai‘i present challenges for estimating the probabilities of earthquakes using methods developed for standard probabilistic seismic hazard analysis (PSHA). A particular problem is that the volcanic processes vary over time, and PSHA usually considers only tectonic earthquakes with stationary rate. A distinct challenge lies in quantifying the hazard due to seismicity associated with the 2018 Kīlauea eruption and the collapse of the summit caldera. During the eruption, M~5 caldera collapse earthquakes, characterized by long period ground motions, occurred almost daily from mid-May until the beginning of August. While such caldera collapses happen infrequently, these caldera collapse earthquakes damaged nearby structures, and these events should therefore be included in a complete seismic hazard assessment. We present an approach to forecast the rate of these caldera collapse events for use in seismic hazard assessments. We model their occurrence by combining a distribution for the occurrence of the underlying process of caldera collapses with a distribution for the number of earthquakes that occur in response to those collapses. We use a Poisson distribution for the number of collapses and a negative binomial distribution for the number of earthquakes in a collapse, using distribution parameters based on historical observations at Kīlauea. This rate model can then be combined with an appropriate ground motion model that accounts for the deficiency in short period ground motions observed in 2018 to assess the seismic hazard posed by caldera collapse events. The event occurrence model is non-Poissonian but can be approximated as Poissonian for low exceedance probabilities (e.g., <10% in 50 years). This approach could also be used more generally to model the hazard due to aftershocks, which can be considered the earthquake response to the underlying process of mainshocks.

Presenting Author: Andrea L. Llenos

Student Presenter: No

Authors