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How Will Earthquakes Change Sea Level? a Probabilistic Coast-Seismic Hazard Model

Description: 

Coseismic uplift and subsidence can cause near-instantaneous meter-scale relative sea level changes that may exacerbate or reverse the effects of ongoing sea level rise. Characterizing hazards in tectonically active coastal regions, therefore, requires careful consideration of coseismic vertical deformation. We developed a proof-of-concept probabilistic model that forecasts coseismic vertical displacement over 100 years in the Wellington Region of Aotearoa New Zealand. This model repurposes fault source, earthquake rupture, and epistemic uncertainty data from the New Zealand National Seismic Hazard Model (NZ NSHM) to quantify the magnitude, direction, location, and likelihood of vertical displacement from both crustal fault and subduction interface earthquakes. The model results suggest that both crustal fault and subduction sources contribute to significant (>0.2 m) vertical displacement hazard at most coastal Wellington sites. In general, the subduction interface contributes more to subsidence hazard while crustal faults contribute more to uplift hazard, though proximity to specific faults and fault geometry influence the hazard at specific sites. Coseismic subsidence, in particular, can be generated by both crustal and subduction earthquakes and should be considered in sea-level rise forecasts and resilience planning. Future versions of this model may benefit from refinements to crustal fault geometries at depth and subduction interface rupture extents. Overall, this study highlights how assumptions and choices in regional scale hazard models underpin coseismic multi-hazard analysis. With the appropriate considerations, however, ground-shaking hazard models may also be useful for estimating coseismic vertical deformation and associated sea level changes in other regions worldwide, particularly where several different seismic sources contribute to hazard.

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: Jaime

Student Presenter: Yes

Invited Presentation: 

Authors