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A Regional Earthquake-Triggered Landslide Susceptibility Map of the Cook Inlet Region, Southcentral Alaska

Description: 

Cook Inlet spans southcentral Alaska from the Gulf of Alaska to the Anchorage and Matanuska-Susitna boroughs, and the surrounding watershed holds the state’s largest population. Cook Inlet is also a forearc basin of the Aleutian Trench, one of the most seismically active subduction zones globally. Surficial geologic units in the region include many loosely consolidated glacial sediments. The region has experienced devastating landslides, especially those triggered by the 1964 Great Alaska earthquake. These factors, in addition to the availability of detailed regional geologic maps, elevation models, and regional earthquake-triggered ground failure inventories, make the Cook Inlet region an important location for landslide susceptibility mapping. Motivated by the need to improve the global U.S. Geological Survey (USGS) near-real-time ground failure product with higher-quality regional information, we developed an earthquake-triggered landslide susceptibility map for the Cook Inlet region. We adapted methods originally proposed by Wilson and Keefer (1985) which combine slope and rock strength to assign classes of relative landslide susceptibility. The resulting relative landslide susceptibility classes range from 0 to 10, with a general trend of shallower slopes and stronger rocks showing less susceptibility, and steeper slopes and weaker rocks being more susceptible. We use this map as the input for two modeling approaches: 1) the HAZUS methodology and 2) a qualitatively updated version of the global model used by the USGS landslide near-real-time product. We compare these results to two newly available detailed inventories of earthquake-triggered ground failure from two large earthquakes in the region: the 1964 Great Alaska Earthquake and the 2018 Anchorage Earthquake. We note that even though we use the susceptibility map with earthquake triggers, the map is also useful for landslide hazards in general and uses a susceptibility classification method common to other regional maps.

Session: Regional-Scale Hazard, Risk and Loss Assessments - I

Type: Oral

Date: 5/2/2024

Presentation Time: 05:30 PM (local time)

Presenting Author: Sonia

Student Presenter: No

Invited Presentation: 

Authors