Abstract
SummaryMegathrust earthquake sequences, comprising mainshocks and triggered aftershocks along the subduction interface and in the overriding crust, can impact multiple buildings and infrastructure in a city. The time between the mainshocks and aftershocks usually is too short to retrofit the structures; therefore, moderate‐size aftershocks can cause additional damage. To have a better understanding of the impact of aftershocks on city‐wide seismic risk assessment, a new simulation framework of spatiotemporal seismic hazard and risk assessment of future M9.0 sequences in the Cascadia subduction zone is developed. The simulation framework consists of an epidemic‐type aftershock sequence (ETAS) model, ground‐motion model, and state‐dependent seismic fragility model. The spatiotemporal ETAS model is modified to characterise aftershocks of large and anisotropic M9.0 mainshock ruptures. To account for damage accumulation of wood‐frame houses due to aftershocks in Victoria, British Columbia, Canada, state‐dependent fragility curves are implemented. The new simulation framework can be used for quasi‐real‐time aftershock hazard and risk assessments and city‐wide post‐event risk management.
Highlights
Recent M9.0 earthquake sequences, such as the 2004 Aceh-Andaman earthquake, the 2010 Maule earthquake, and 2011 Tohoku earthquake, triggered large aftershock events (e.g., M≥7.0) on the subduction interface and in the overriding crust, demonstrating the destructive effects of aftershocks on buildings [1,2]
This section discusses the impact of mainshocks and aftershocks from the Cascadia subduction zone (CSZ) on the municipality-wide seismic risk assessment in Victoria
This study developed a new simulation framework to assess spatiotemporal seismic hazard and risk due to M9.0 mainshock-aftershock sequences using a realistic building portfolio of wood-frame houses for Victoria, British Columbia (BC), Canada
Summary
Recent M9.0 earthquake sequences, such as the 2004 Aceh-Andaman earthquake, the 2010 Maule earthquake, and 2011 Tohoku earthquake, triggered large aftershock events (e.g., M≥7.0) on the subduction interface and in the overriding crust, demonstrating the destructive effects of aftershocks on buildings [1,2]. Because the time to repair damaged buildings between a mainshock and aftershocks is often short, the cumulative damage effect of buildings due to aftershocks can have a significant impact on post-earthquake risk assessment [3,4,5]. A spatiotemporal seismic risk assessment that considers the cumulative damage effect due to M9.0 earthquake sequences is necessary to quantify the impact of aftershocks on post-event risk management decision-making, including resource allocation, evacuation planning, and rapid seismic loss estimation [6,7]. In the urban areas (e.g., Vancouver and Victoria) of BC, a large number of wood-frame houses [11] may be at risk from M9.0 subduction earthquake sequences
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