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Validation of Probabilistic Coseismic Coastal Deformation Models using Geologic and Geomorphic Evidence

Description: 

Incorporating the likelihood of sudden earthquake-driven coastal uplift or subsidence into sea level change forecasts is important in tectonically active countries such as Aotearoa New Zealand (A-NZ). Several historical earthquakes in A-NZ have demonstrated the impacts that sudden coastal displacement can have on society, the environment and infrastructure. A proof-of-concept probabilistic model that forecasts coseismic vertical displacement over 100 years in the Wellington Region of A-NZ has been developed, and there is an intention to expand this model nationwide. Alongside this is a need to develop methods of validating the probabilistic coseismic coastal deformation results. Validation of the coastal deformation model can be done through a comparison with historical and some prehistoric coastal deformation data. The A-NZ historical record is short (~185 years) but there have been 6 earthquakes that have caused coastal deformation within this period. The prehistoric coastal deformation record is much longer but precisely how we compare geologic and geomorphic evidence of past coastal uplift and subsidence with modeling results is challenging. For example, the modeled coseismic displacements represent a mix of permanent and elastic tectonic deformation but the geomorphic record preserves net permanent displacement over multiple seismic cycles, so the geomorphic record may under-represent displacements from primarily elastic subduction zone earthquakes. We are exploring whether net uplift/subsidence rates from Pleistocene marine terraces are a useful source of data, or whether recurrence intervals and single-event displacement data from Holocene sedimentary and geomorphic records are preferable. However, using single-event displacement necessitates some understanding of the preservation and detection limits of various coastal paleoseismic proxies. Regardless of the approach, model validation is important for establishing confidence in the results and for targeting which model input parameters may benefit from further research.

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: Kate

Student Presenter: No

Invited Presentation: 

Authors