Periodically Triggered Seismicity at Mount Wrangell, Alaska, After the Sumatra Earthquake

Document Type


Publication Date


Digital Object Identifier (DOI)



As surface waves from the 26 December 2004 earthquake in Sumatra swept across Alaska, they triggered an 11-minute swarm of 14 local earthquakes near Mount Wrangell, almost 11,000 kilometers away. Earthquakes occurred at intervals of 20 to 30 seconds, in phase with the largest positive vertical ground displacements during the Rayleigh surface waves. We were able to observe this correlation because of the combination of unusually long surface waves and seismic stations near the local earthquakes. This phase of Rayleigh wave motion was dominated by horizontal extensional stresses reaching 25 kilopascals. These observations imply that local events were triggered by simple shear failure on normal faults.

Was this content written or created while at USF?


Citation / Publisher Attribution

Science, v. 308, issue 5725, p. 1144-1146