Dura Tina, Chilton William, Small David, Garner Andra J, Hawkes Andrea, Melgar Diego, Engelhart Simon E, Staisch Lydia M, Witter Robert C, Nelson Alan R, Kelsey Harvey M, Allan Jonathan C, Bruce David, DePaolis Jessica, Priddy Michael, Briggs Richard W, Weiss Robert, La Selle SeanPaul, Willis Michael, Horton Benjamin P
Department of Geosciences, Virginia Tech, Blacksburg, VA 24061.
Water Resources, Singhofen Halff Associates, Orlando, FL 32817.
Proc Natl Acad Sci U S A. 2025 May 6;122(18):e2424659122. doi: 10.1073/pnas.2424659122. Epub 2025 Apr 28.
Climate-driven sea-level rise is increasing the frequency of coastal flooding worldwide, exacerbated locally by factors like land subsidence from groundwater and resource extraction. However, a process rarely considered in future sea-level rise scenarios is sudden (over minutes) land subsidence associated with great (>M8) earthquakes, which can exceed 1 m. Along the Washington, Oregon, and northern California coasts, the next great Cascadia subduction zone earthquake could cause up to 2 m of sudden coastal subsidence, dramatically raising sea level, expanding floodplains, and increasing the flood risk to local communities. Here, we quantify the potential expansion of the 1% floodplain (i.e., the area with an annual flood risk of 1%) under low (0.5 m), medium (1 m), and high (~2 m) earthquake-driven subsidence scenarios at 24 Cascadia estuaries. If a great earthquake occurred today, floodplains could expand by 90 km (low), 160 km (medium), or 300 km (high subsidence), more than doubling the flooding exposure of residents, structures, and roads under the high subsidence scenario. By 2100, when climate-driven sea-level rise will compound the hazard, a great earthquake could expand floodplains by 170 km (low), 240 km (medium), or 370 km (high subsidence), more than tripling the flooding exposure of residents, structures, and roads under the high subsidence scenario compared to the 2023 floodplain. Our findings can support decision-makers and coastal communities along the Cascadia subduction zone as they prepare for compound hazards from the earthquake cycle and climate-driven sea-level rise and provide critical insights for tectonically active coastlines globally.
气候驱动的海平面上升正在增加全球沿海洪水的发生频率，而诸如地下水开采和资源开采导致的地面沉降等因素又在局部地区加剧了这种情况。然而，在未来海平面上升情景中很少被考虑的一个过程是与强烈（震级>M8）地震相关的突然（数分钟内）地面沉降，沉降量可能超过1米。沿着华盛顿州、俄勒冈州和加利福尼亚州北部海岸，下一次卡斯卡迪亚俯冲带大地震可能导致高达2米的沿海突然沉降，大幅抬高海平面，扩大洪泛区，并增加当地社区的洪水风险。在此，我们量化了24个卡斯卡迪亚河口在低（约0.5米）、中（约1米）和高（约2米）地震驱动沉降情景下1%洪泛区（即年洪水风险为1%的区域）的潜在扩张情况。如果今天发生一场大地震，洪泛区可能会扩张90公里（低沉降）、160公里（中沉降）或300公里（高沉降），在高沉降情景下，居民、建筑物和道路遭受洪水侵袭的面积将增加一倍以上。到2100年，当气候驱动的海平面上升使灾害情况更加复杂时，一场大地震可能会使洪泛区扩张170公里（低沉降）、240公里（中沉降）或370公里（高沉降），与2023年的洪泛区相比，在高沉降情景下，居民、建筑物和道路遭受洪水侵袭的面积将增加两倍以上。我们的研究结果可为卡斯卡迪亚俯冲带沿线的决策者和沿海社区应对地震周期和气候驱动的海平面上升带来的复合灾害提供支持，并为全球构造活跃的海岸线提供关键见解。
