Spatiotemporal seismic hazard and risk assessment of M9.0 megathrust earthquake sequences of wood‐frame houses in Victoria, British Columbia, Canada

Abstract

Megathrust 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.

Universal Non-Extensive Statistical Physics Temporal Pattern of Major Subduction Zone Aftershock Sequences

“…This is achieved by estimating the parameters of various well-established empirical laws for aftershock sequences following major mainshocks in a specific seismogenic region [ 6 , 7 , 8 ]. In a subduction zone, the intense friction between the descending and overriding plates may generate shallow, intermediate, or deep earthquakes, which may occur both within the descending and overriding plates as well as along the interface between the two plates [ 9 , 10 ]. The magnitudes of such earthquakes vary greatly, depending on the sorts of boundaries that cause them.…”

Relative Afterslip Moment Does Not Correlate With Aftershock Productivity: Implications for the Relationship Between Afterslip and Aftershocks

“…The Thingbaijam et al. (2017) scaling relations provide reasonable approximations of mainshock dimensions and aftershock zone size, even for large subduction earthquakes (Zhang et al., 2020, 2021). For each mainshock, we conduct a broad preliminary search for seismicity within 2 l maj of the mainshock epicenter (Figure 1a) and use this to define the average location of seismicity.…”

“…We scale l maj and l min with mainshock size and mechanism based on the recent mainshock rupture scaling relations by Thingbaijam et al (2017) and considering mainshock dip angle from the GCMT catalog (Dziewonski et al, 1981;Ekström et al, 2012). The Thingbaijam et al (2017) scaling relations provide reasonable approximations of mainshock dimensions and aftershock zone size, even for large subduction earthquakes (Zhang et al, 2020(Zhang et al, , 2021. For each mainshock, we conduct a broad preliminary search for seismicity within 2l maj of the mainshock epicenter (Figure 1a) and use this to define the average location of seismicity.…”

Probabilistic risk assessment for reinforced concrete frame structures subject to mainshock‐aftershock sequences

“…Typically, there is insufficient time between the MS and its AS to adequately repair the damaged buildings. 1,2 In such cases, some strong ASs can cause additional damage and increase the seismic risk for the mainshock-damaged structures. For instance, a residential building was slightly damaged after the MS of the 1999 Turkey earthquake.…”