120-3 Assessing the Impact of Coastal Subsidence on Tsunami Hazards Along the U.S. West Coast using Sentinel-1 InSAR and Numerical Modeling

Session: Land Surface Subsidence: Processes, Impacts, and Ongoing Challenges

Presenting Author:

Authors:

Abstract:

Coastal subsidence along tectonically active regions of the U.S. West Coast presents a significant hazard by exacerbating the impacts of tsunami inundation. Subsidence, which refers to the sinking or settling of land surfaces, can vary spatially and temporally due to various factors, including tectonic processes, groundwater extraction, and sediment compaction. The combined effects of subsidence and tsunami events are poorly understood, especially in areas where both phenomena are present. This study aims to fill this gap by employing high-resolution geodetic data from Sentinel-1 Synthetic Aperture Radar (SAR) and Small Baseline Subset (SBAS) [1] InSAR (Interferometric Synthetic Aperture Radar) analysis to assess coastal subsidence and its impact on tsunami risk along the U.S. West Coast. Using SBAS InSAR analysis, we analyze both ascending and descending Sentinel-1 tracks to capture land motion in key regions known for their subsidence hotspots [2][3]. By focusing on the Cascadia Subduction Zone, a tectonically active region characterized by the potential for large megathrust earthquakes, we aim to quantify subsidence rates and trends. Similarly, areas in the San Francisco Bay and Southern California, which also experience varying rates of subsidence, are analyzed to understand how these local deformations influence tsunami wave propagation and impact. Our analysis of vertical land motion is  integrated with a tsunami propagation and inundation model, which simulates tsunami wave heights, arrival times, and coastal flooding extent. We assess how varying rates of subsidence in these regions modify tsunami dynamics, comparing results to existing tsunami models that do not account for such localized land motion [4]. The results offer valuable insights for hazard mitigation planning and coastal management, helping to reduce risk and enhance preparedness in tsunami-prone regions.

References:

[1] Lanari, R., et al., A small-baseline approach for investigating deformations on full-resolution differential SAR interferograms. IEEE transactions on geoscience and remote sensing, 2004. 42(7): p. 1377-1386

[2] Shirzaei, M. and R. Bürgmann, Global climate change and local land subsidence exacerbate inundation risk to the San Francisco Bay Area. Science advances, 2018. 4(3): p. eaap9234.

[3] Ohenhen, L.O., et al., Disappearing cities on US coasts. Nature, 2024. 627(8002): p. 108-115.

[4] Tung, S. and T. Masterlark, Finite Element Models of Elastic Earthquake. Earthquakes: Forecast, Prognosis and Earthquake Resistant Construction, 2018: p. 169.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

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