Slow Earthquakes Occur Continuously in the Alaska-Aleutian Subduction Zone

UCR Today


UC Riverside study reports nearly continuous tremor and 1,300 low frequency earthquakes in this region
By Iqbal Pittalwala on July 12, 2017
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Image shows tremor sources and low frequency earthquake distribution in the study region and historic large earthquakes in the Alaska-Aleutian subduction zone. Each red star represents the location of 1 min tremor signal determined by the beam back projection method, and the black stars show three visually detected low frequency earthquakes located using arrival times of body waves. Image credit: Ghosh lab, UC Riverside.

RIVERSIDE, Calif. – Seismologists at the University of California, Riverside studying earthquakes in the seismically and volcanically active Alaska-Aleutian subduction zone have found that “slow earthquakes” are occurring continuously, and could encourage damaging earthquakes.
Slow earthquakes are quiet, can be as large as magnitude 7, and last days to years. Taking place mainly at the boundary between tectonic plates, they happen so slowly that people don’t feel them. A large slow earthquake is typically associated with abundant seismic tremor—a continuous weak seismic chatter—and low frequency (small and repeating) earthquakes.
“In the Alaska-Aleutian subduction zone, we found seismic tremor, and visually identified three low frequency earthquakes,” said Abhijit Ghosh, an assistant professor of Earth sciences, who led the research published recently in Geophysical Research Letters. “Using them as templates, we detected nearly 1,300 additional low frequency earthquakes. Slow earthquakes may play an important role in the earthquake cycles in this subduction zone.”
The Alaska-Aleutian subduction zone, which stretches from the Gulf of Alaska to the Kamchatka Peninsula in the Russian Far East, is one of the most active plate boundaries in the world. It is 3,800 km long and forms the plate boundary between the Pacific and North American plates. In the last 80 years, four massive earthquakes (greater than magnitude 8) have occurred here.
Abhijit Ghosh lands in Alaska to do field work. Photo credit: Ghosh lab, UC ...

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