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WITHDRAWN Seismic Hazard from the Aftershocks of Subduction Interface Earthquakes

Description: 

WITHDRAWN Large Mw ≥ 8.0 subduction interplate earthquakes (also called megathrust earthquakes) typically trigger intense and prolonged aftershock sequences. While the main slip of the initial megathrust event typically occurs off-shore, the associated aftershocks are spatially more diverse and may occur closer to built environments. Given the potential proximity of aftershocks to communities, and the likelihood of them having magnitudes greater than Mw6.0, the aftershocks pose a significant societal threat. Recognizing the need to better understand the temporal and spatial distribution of damaging aftershocks following large subduction interface earthquakes, we compile and present an analysis of aftershock catalogues from 11 instrumentally recorded subduction interface earthquakes of Mw ≥ 8.0 from around the world. We compare aftershock activity rates to the baseline seismic activity rate before the mainshock for crustal, intraslab and interface aftershocks for each of these 11 subduction interface events. The annualized relative increase in seismic activity for all three types of earthquakes is at least two-fold. With respect to the largest aftershocks (Mw ≥ 6.5), we find that the vast majority of them occur within a zone proximal to the subduction trench and within the upper 50 km depth, regardless of whether they are crustal, intraslab or interplate aftershocks. With rare exceptions, the b-values for aftershock sequences are similar. This allows a comparison of the aftershock productivity of various subduction zones. We use this dataset to model activity rates and seismic hazard from subduction aftershock sequences spatially and temporally. Finally, based on these findings, we present (i) preliminary modelling of the activity rates of a future Cascadia subduction interface earthquake aftershock sequence, (ii) preliminary estimates of seismic hazard from a Cascadia aftershock sequence, and (iii) an initial analysis of spatial and temporal variation in aftershock hazard.

Session: New Directions in Environmental, Seismic Hazard and Mineral Resource Exploration Studies - II

Type: Oral

Date: 4/17/2025

Presentation Time: 04:45 PM (local time)

Presenting Author: Tuna

Student Presenter: No

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