Nonvolcanic Tremor in the Aleutian Arc

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Nonvolcanic tremors (NVT) have been observed across the Aleutian arc. The tremorlike events are observed over a large region spanning seismic networks on several volcanoes and are therefore unlikely to be related to any one volcanic complex. Although locating the events is not possible at the present time, we provide general locations based on move-out times and amplitudes across multiple networks. The majority of NVT events are recorded in regions where the subducting Pacific plate is inferred to be locked or transitioning from creeping to locked. One NVT event was recorded during a time of increased seismic and volcanic activity in the area near the Rat and Andreanof Islands. Similar simultaneous increases have been observed in the Aleutians in the past and are hypothesized to be caused by large regional stress changes, possibly caused by slow-slip events. A prominent recent NVT event was recorded on the Korovin and Great Sitkin seismic networks approximately one hour after the onset of the 12 July 2008 eruption of Okmok volcano. NVT does not appear sporadically across the Aleutian arc but seems to concentrate in a few regions. With 2500 km of subduction zone, we have an opportunity to examine these regions and compare them to regions not producing NVT in an attempt to identify factors that may play a role in its creation.

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Bulletin of the Seismological Society of America, v. 101, no. 6, p. 3081-3087