Landslide-Induced Tsunamis of Southern Alaska

Science Center Objects

Working with partners to study and inform the Nation about geohazard risks

One example of how the CMHRP works with partners to study and inform the Nation about geohazard risks is the collaborative research conducted with colleagues from Boise State University and the Alaska Department of Fish and Game on the links between earthquakes, submarine landslides, and tsunamis across southern Alaska. The Great Alaska Earthquake of 1964 (magnitude 9.2) was associated with a destructive tsunami that affected a wide swath of southern Alaska’s coastline both during and immediately following the earthquake. This event generated two types of ocean waves. Sudden crustal movement that caused the earthquake produced long-period ocean waves that propagated across the Pacific Ocean as far as Antarctica. Shorter period ocean waves were generated locally within the enclosed fjords and straits of southern Alaska and were related to offshore landslides. These shorter period waves had catastrophic effects on the coastal communities of Valdez, Seward, and Whittier.

Photograph shows what remains of a building foundation in the foreground and a house in the background and up a slight elevation

Photograph taken in 1964 of the main part of the Chenega village site in Alaska. Pilings in the ground mark the former locations of homes swept away by tsunami waves. The schoolhouse on high ground was undamaged. Credit: Figure 6 from Plafker et al. (1969).

Vintage photograph showing a flooded coastal area, water is up to the roof of a house in the background.

Magnitude 9.2: The 1964 Great Alaska Earthquake” is a short video relating how the largest quake in U.S. history had profound and lasting impacts on our lives. » View the video

 

Three-dimensional cartoon showing features of an area of the seafloor in relief, near a coastline.

Perspective view of a large submarine landslide offshore Seward, Alaska (see white arrow). The CMHRP collected the data that show seafloor topography. From H.J. Lee, et al., 2003.

Map of Alaska shows the location of the epicenter of the huge earthquake of 1962 and locations of subsequent tsunamis.

Map of Prince William Sound. Triangles indicate the locations of local tsunamis that occurred during the 1964 Great Alaska Earthquake (red star marks the epicenter). Red triangles mark tsunamis linked to submarine landslides. White triangles mark tsunamis of unexplained origin. Blue shading indicates areas of large ice fields and active glaciers.

The CMHRP is mapping and dating submarine landslide deposits in this area to determine how frequently earthquakes occurred in the past in order to infer when they might happen in the future. For the 1964 earthquake, observations on land indicate how high the ocean water levels rose during the tsunami, and models provide insight about seismic wave patterns. This information, coupled with new offshore geophysical data that constrain landslide distribution, geometry, and size, support reconstruction of prehistoric events as well as coastal risk assessments related to future submarine slides.

Four people looking a flattened trees

USGS scientists investigate trees knocked over by the tsunami at the mouth of Taan Fjord, Alaska. The tsunami was triggered by a landslide on October 17, 2015, at the head of the fjord. Flow depth here was likely 5 meters based on the height of branches stripped off trees in the background. This event had the fourth highest tsunami runup ever recorded. Credit: Peter Haeussler, USGS