Climate change and seismic resilience: Key considerations for Alaska’s infrastructure and built environment

in Anchorage, Alaska and the other half joined remotely via videoconference. The analysis and synthesis across these sources initially applied an engineering perspective, followed by a cou- pled human-environment systems perspective. Results and discussion Synthesis of engineering and physical science findings Hazards and vulnerability of infrastructure systems influence the risk of disasters. Past research addresses factors influencing vulnerability [21] and natural disaster losses [22–24]. Seismic risk and associated infrastructure vulnerability vary considerably across the state of Alaska. Fig 3A shows the National Risk Index (NRI) in Alaska determined based on earth- quake hazard, combining earthquake expected annual loss, social vulnerability, and commu- nity resilience. Detailed documentation regarding the NRI and its derivation can be found in the NRI technical documentation [25]. Fig 3A indicates that Northern Arctic areas have “very low” seismic risk while central and south-central areas have “relatively low” to “relatively mod- erate” risk. The seismic hazard distribution and population density throughout Alaska greatly influence these variations. Climate change compounds these cumulative risks, threatening Alaskan communities with sea level rise, thawing permafrost, melting sea and land ice, and increased precipitation [7, 26–28]. Berman and Schmidt [29] estimated the economic costs of these climate-induced stressors in Alaska to be roughly $310 to $530 million (in 2022 US dol-

lars) annually over the next 30–50 years. This estimate includes highly likely and easily quanti- fied costs such as protection, maintenance, and repair of public infrastructure; community relocation; wildfire fighting and property loss, and replacement of ice roads. This estimate does not account for less certain or cascading direct and indirect costs such as those associated with private infrastructure, interruptions to drinking water or sewage services [30], temporary displacement of residents [31, 32], public health risks [33, 34], threats to monetized or subsis- tence livelihoods [34–37], and intensified labor demands to sustain formal and informal social networks [38]. It is important to note that the assessment of indirect losses is particularly important when evaluating the organizational and social aspects of climate change and earth- quake damage on the entire community [39–41]. Coastal erosion resulting from climate- induced threats has caused several Alaskan communities to seek partial or total relocation [42]. Thawing permafrost is also generating widespread infrastructure damage to systems not at direct risk of erosion [7, 43, 44]. These damages shorten the useful life of buildings and lead to early retrofit and replacement. Cognizant of these converging threats, workshop participants identified three leading cli- mate-induced seismic infrastructure resilience concerns: (1) permafrost thaw and soil liquefac- tion, (2) lack of redundancy in lifeline infrastructure, and (3) cascading seismic effects. According to one structural engineer,

[Permafrost melt] may change how seismic waves travel if the soil is softer as it melts. But also, it starts creating problems for the piles [deep foundations] and they start losing capac- ity. You may end up with overturning failure. . . failure of a pile due to the fact that it doesn’t have the capacity you thought it was going to have. Fig 3B synthesizes geographic information on seismic hazard [48] with permafrost distribu- tions [45], uniquely identifying regions in Alaska where a changing climate will most likely affect seismic vulnerability and resilience. According to the figure, permafrost underlies about 75% of Alaska, roughly 800,000 km2, and is subject to the varied effects of climatic change [49]. Chadburn and coauthors [50] estimate that for every 1°C annual average temperature PLOS ONE Climate change and seismic resilience: Key considerations for Alaska’s infrastructure and built environment PLOS ONE | https://doi.org/10.1371/journal.pone.0292320 October 18, 2023 5 / 17