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Periodically-triggered seismic events at Mt. Wrangell Volcano, Alaska following the Sumatra-Andaman Islands earthquake. Mt. Wrangell is one of the largest andesite shield volcanoes in the world. It exhibits fumerolic activity and occasional steam plumes. Because of its volcanic and seismic activity, a network of short period seismometers is operated at Wrangell by the Alaska Volcano Observatory. Following the Sumatra-Andaman Islands earthquake on December 26, 2004 Mt. Wrangell had a swarm of seismic events ranging in magnitude from -0.3 to 1.9. These events occurred as the large amplitude surface waves from the Sumatra-Andaman earthquake crossed the region. This is remarkable since Mt. Wrangell is nearly 11,000 km from the epicenter. While swarms are not uncommon at Wrangell, the events in this swarm occur at intervals of 20-30 seconds in-phase with the teleseismic ground motion. This suggests that the events were triggered by individual pulses within the teleseismic wavetrain.
Credits: Data is provided by the Alaska Volcano Observatory and the Alaska Earthquake Information Center. The Alaska Volcano Observatory is a cooperative effort of the Geophysical Institute at the University of Alaska Fairbanks, the U.S. Geological Survey, and the State of Alaska Division of Geological and Geophysical Surveys. Origin times were provided by John Sanchez at the University of Alaska Fairbanks.
Figure by Michael West, Alaska Volcano Observatory and University of Alaska Fairbanks