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Journal: |
Journal of Geophysical Research 2020 No.1
clicks:254 |
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Title:
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Author:
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Satoru Baba1 , Akiko Takeo1 , Kazushige Obara1 , Takanori Matsuzawa2 , and Takuto Maeda |
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Adress: |
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Abstract:
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Very low frequency earthquakes (VLFEs), classified as one type of slow earthquake, occur near
seismogenic zones and can be a proxy for interplate slow slip. We investigated VLFE activity off the
Hokkaido and Tohoku Pacific coasts, where the Pacific plate subducts under the North American plate.
Comprehensive detection of VLFEs is performed for the period from January 2003 to July 2018 by a
matched‐filter technique utilizing synthetic waveforms calculated based on a three‐dimensional velocity
structure model. The spatiotemporal consistency between the afterslip of the 2003 Tokachi‐Oki earthquake
(Mw 8.0) and VLFE distribution off the Hokkaido coast suggests that VLFE activity can reflect interplate
slow slip. Inside a large coseismic slip area of the 2011 Tohoku earthquake (Mw 9.0), the VLFE activity was
low thereafter, whereas outside the area, VLFE activity increased after the 2011 Tohoku earthquake.
These characteristics are consistent with aseismic slip distributions estimated from repeating earthquakes.
VLFEs were sometimes activated by afterslips of interplate earthquakes with Mw of 6–7, such as the 2008
Fukushima‐Oki earthquake and aftershocks of the 2011 Tohoku earthquake. Even in the coseismic slip
areas of very large earthquakes, we found the occurrence of episodic bursts every 3 months to a year during
an interseismic period between very large earthquakes. Such VLFE bursts may suggest small slips during the
interseismic period. |
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Comment: |
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