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Published 2012 | metadata_only
Journal Article

Migration process of very low-frequency events based on a chain-reaction model and its application to the detection of preseismic slip for megathrust earthquakes


In order to reproduce slow earthquakes with short duration such as very low frequency events (VLFs) migrating along the trench direction as swarms, we apply a 3-D subduction plate boundary model based on the slowness law of rate- and state-dependent friction, introducing close-set numerous small asperities (rate-weakening regions) at a depth of 30 km under high pore pressure condition, in addition to a large asperity. Our simulation indicates that swarms of slip events occur repeatedly at the small asperities, and these events are similar to the observed slow earthquake group, especially to VLF, on the basis of the relation between characteristic duration and seismic moment. No slip events occur there without the small asperities, which mean that the close-set numerous small asperities may be one of the necessary conditions for generating the short-duration slow earthquakes such as VLFs. In the preseismic stage of the megathrust earthquakes that occur at the large asperity, the swarms of VLFs have higher migration speeds and higher moment release rate as well as shorter recurrence interval. Thus, monitoring the migration of slow earthquakes may be useful in imaging the preseismic slip of megathrust earthquakes.

Additional Information

© 2012 Society of Geomagnetism and Earth, Planetary and Space Sciences. Received March 29, 2010; Revised September 29, 2010; Accepted September 30, 2010; Online published August 27. 2012. The authors would like to thank Dr. Kazushige Obara and Dr. Bunichiro Shibazaki for their fruitful discussion, which helped to narrow the target of our simulation. Thoughtful comments from N. Kato and an anonymous reviewer kindly helped us to improve this manuscript. The present study used the Earth Simulator and the supercomputing resources at the Cyberscience Center of Tohoku University. GMT software (Wessel and Smith, 1998) was used to draw a number of the figures. The present study was supported by the DONET program of the Ministry of Education, Culture, Sports, Science and Technology.

Additional details

August 19, 2023
August 19, 2023