New research finds that large earthquakes can trigger underwater landslides thousands of miles away, weeks or months after the quake occurs.
Researchers analyzing data from ocean-bottom seismometers off the Washington-Oregon coast tied a series of underwater landslides on the Cascadia Subduction Zone to a 2012 magnitude-8.6 earthquake in the Indian Ocean — more than 8,000 miles away. These underwater landslides occurred intermittently for nearly four months after the April earthquake. Previous work has shown that earthquakes can trigger additional earthquakes on other faults, but this study shows they can also initiate undersea landslides far from the quake.
“The basic assumption is that these marine landslides are generated by the local earthquakes,” said Paul Johnson, an oceanographer at the University of Washington and lead author of the new study published in the Journal of Geophysical Research: Solid Earth, a journal of the American Geophysical Union. “But what our paper said is, ‘No, you can generate them from earthquakes anywhere on the globe.’”