Continuous Tremor in the Alaska-Aleutian Subduction Zone Detected by Aleutian Array of Arrays

Bo Li, Abhijit Ghosh, Clifford H. Thurber, & Federica Lanza

Submitted August 15, 2017, SCEC Contribution #7758, 2017 SCEC Annual Meeting Poster #066

Previous studies show tremor activities represent slips on small asperities due to slow slip in the surrounding region [e.g., Bartlow et al, 2011; Ghosh et al., 2012]. Therefore, their spatiotemporal distribution, migration directions, patterns and speeds can provide clues about the dynamics of the slow earthquakes and the physical asperities on the subuduction interface. To better study tremors, other slow earthquakes, structure and the seismicity in the Alaska-Aleutian subduction zone, one of the most seismically and volcanically active plate boundaries on earth, in 2014 we installed a hybrid array of arrays, that consisted of three well-designed mini seismic arrays and five stand alone stations. They were operational in continuous mode for one to two years. For about one year when all three arrays are running, we use the beam back-projection method [Ghosh et al., 2009, 2012] to detect continuous tremor activities, with an average of more than two hours of activity per day. The tremor sources are located to the south of the Unalaska and Akutan Islands, at the eastern and down-dip edge of the rupture zone of the 1957 Mw 8.6 earthquake. They are heterogeneously distributed along the strike of the subduction zone in the study region. Tremors are clustered in several patches, with a less active gap between two major clusters. We also observe multiple tremor migration patterns with propagation in both short- and long-time scale. In short-time scale, over a few minutes to a few hours, tremors show unidirectional or reverse migrations along-strike and dip directions, with a wide range of velocities. There is also a three-month tremor migration to the northwest, with a velocity about 1.2 km per day. In addition, we also detect tens of LFE families and they are spatiotemporally consistent with tremor activities. This study of prolific tremor activities in the Aleutians detected by the array techniques is helping us better recognize the heterogeneous physical asperities of the transition zone, and providing an opportunity to explore potential relationship between slow and fast earthquakes.

Key Words
Tremor, migration, Alaska-Aleutian

Citation
Li, B., Ghosh, A., Thurber, C. H., & Lanza, F. (2017, 08). Continuous Tremor in the Alaska-Aleutian Subduction Zone Detected by Aleutian Array of Arrays. Poster Presentation at 2017 SCEC Annual Meeting.


Related Projects & Working Groups
Seismology