2024-03-28T17:38:32Z
https://soar-ir.repo.nii.ac.jp/oai
oai:soar-ir.repo.nii.ac.jp:00012435
2022-12-14T04:07:31Z
1221:1222
Fault extent of the largest aftershock of the 1968 Tokachi-Oki, Japan, earthquake and an interpretation of the normal faulting focal mechanism
Izutani, Yasuo
Copyright© 2011 The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.
1968 Tokachi-Oki earthquake
largest aftershock
fault extent
normal faulting
reversal of focal mechanisms
The focal mechanism of the 1968 Tokachi-Oki earthquake (MJ = 7.9) was thrust faulting but that of the largest aftershock (MJ = 7.5) was normal faulting. The tectonic implication of the reversal of the focal mechanisms of the two events has not been clarified yet. In order to investigate this, we ought to take into account the relative location of the two fault planes. In the present study, the length and the direction of rupture propagation for the largest aftershock is derived from the azimuth dependence of the duration of observed strong ground motion. If we assume that the rupture initiation point is the hypocenter location determined by the Japan Meteorological Agency (JMA), the location of the fault plane is considerably further north of the tsunami source area as estimated previously, and at the northern end of the aftershock area within 24 hours after the main shock. The fault plane of the largest aftershock is deeper than that of the main shock and the two fault planes are nearly parallel to each other. The thrust faulting of the main shock and the normal faulting of the largest aftershock indicate that the part of the Pacific plate between the two fault planes moved relatively further northwestward due to the two events than the deeper part beneath the fault plane of the largest aftershock.
Article
EARTH PLANETS AND SPACE. 63(12):1213-1216 (2011)
TERRA SCIENTIFIC PUBL CO
2011
eng
journal article
VoR
http://hdl.handle.net/10091/14215
https://soar-ir.repo.nii.ac.jp/records/12435
https://doi.org/10.5047/eps.2011.07.018
10.5047/eps.2011.07.018
1343-8832
AA11211921
EARTH PLANETS AND SPACE
63
12
1213
1216
https://soar-ir.repo.nii.ac.jp/record/12435/files/2011_Izutani_EPS.pdf
application/pdf
785.3 kB
2015-09-28