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Toward Resilient Coastal Communities: A Probabilistic Assessment of Co- and Inter-Seismic Vertical Land Motion

Description: 

The Cascadia subduction zone stands out for its capacity to generate great megathrust earthquakes in the future, which can cause abrupt coastal subsidence of a few meters. Thus, it is critical to understand the probabilistic nature of vertical land motion (VLM) along the Pacific Northwest shoreline to minimize the effects on coastal communities and to inform community planners of possible outcomes. Here, we present a probabilistic framework to assess future tectonic VLM to aid in planning. Considering both inter- and co-seismic scenarios, we derive probability density functions (PDFs) of future tectonic VLM for various locations along the coastline. For coseismic PDFs, we first calculate elastic vertical responses at coastal areas to 37,500 “fakequakes” (Melgar, 2021), using a boundary-element modeling tool. We then construct PDFs guided by the logic tree for the National Seismic Hazard Map (NSHM) and geological constraints. Interseismic PDFs are obtained using a geodetic locking model. We scale these PDFs by multiplying estimated likelihoods of co- and inter-seismic scenarios for a return period of interest. We estimate these likelihoods using a Brownian recurrence model that incorporates the mean recurrence interval and aperiodicity of past earthquakes as inputs. Using the turbidite catalog from Goldfinger et al. (2017), for example, we calculated the likelihood of a full-margin megathrust earthquake within the next 50 years to be ~ 15 %, which is consistent with the value used by the NSHM. Applying the total probability theorem, we merge the scaled PDFs to generate total PDFs of tectonic VLM and the associated hazard curves for the coastal areas. This final product, when coupled with sea-level rise and tsunami models, enables community planners to better assess the hazards for coastal communities in the Pacific Northwest. Our comprehensive probabilistic framework may be applied to other subduction zones to foster a better understanding of potential seismic hazards and offer insights to strengthen resilient planning and disaster preparedness efforts worldwide.

Session: Seismic Cycle-Driven Sea-Level Change Over Decades to Centuries: Observations and Projections [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Jeonghyeop

Student Presenter: No

Invited Presentation: 

Authors