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Repeating short- and long-term slow slip events with deep tremor activity around the Bungo channel region, southwest Japan


We report the repeating occurrence of short- and long-term slow slip events (SSE) which are accompanied by deep tremor activity around the Bungo channel region, southwest Japan. Both of these activities are detected by NIED Hi-net, which is composed of densely distributed observatories equipped with a set of tiltmeter and a high-sensitivity seismograph. Since the short-term SSE is small in magnitude, GPS can detect only the long-term SSE. Some of these episodes have nearly the same surface deformation pattern. This shows the existence of ‘slow slip patches’ on a plate interface, where the episodic slow slip is the characteristic slip behavior. We observe a change in periodicity and size of the short-term episode after the onset of the long-term SSE. Moreover, the long-term slow slip accelerates when the short-term activity takes place. This suggests that there is an interaction between these two types of SSEs.


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Correspondence to Hitoshi Hirose.

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Hirose, H., Obara, K. Repeating short- and long-term slow slip events with deep tremor activity around the Bungo channel region, southwest Japan. Earth Planet Sp 57, 961–972 (2005).

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Key words

  • Subduction zone
  • Philippine Sea plate
  • plate interface
  • Hi-net
  • borehole tiltmeter
  • GPS
  • slow slip patch