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Seismicity in the Northern Part of Tohoku District Induced by the 2011 Off the Pacific Coast of Tohoku Earthquake
| Content Provider | Semantic Scholar |
|---|---|
| Author | Kosuga, Masahiro Watanabe, Kazutoshi Hashimoto, Kazuhiro Kasai, Hiroki |
| Copyright Year | 2012 |
| Abstract | We have investigated the inland seismic activity induced by the 2011 Off the Pacifi c coast of Tohoku (Tohoku-oki) Earthquake in the northern part of Tohoku district, using JMA catalog and newly determined focal mechanism solutions. The seismicity is quite high in the Akita prefecture, forming newly activated clusters. The cluster locations are complementary for the periods before and after the Tohoku-oki Earthquake. A stress tensor inversion using focal mechanism data indicates that the stress field has changed from reverse-faulting regime to strike-slip regime, with a counter-clockwise rotation of the maximum principal stress axis and the replacement of the other two principal axes. This change is qualitatively explained by the weakened E-W compressional stress due to megathrust faulting of the Tohoku-oki Earthquake. Thus the new stress fi eld in the investigated area is unfavorable to the preexisting fault planes of reverse faulting, which brought the complementary seismic activity. Among the three active clusters in the Akita prefecture, the one to the north of Moriyoshi volcano is interesting, because the swarm-like activity forms a volumetric source with a dimension of about 3 km. Considering a possible existence of crustal fl uid suggested by a refl ected phase, delayed beginning of seismic activity about 2 month from the Tohoku-oki Earthquake, and the migration of seismic activity, the induced seismic activity in the area may be related to a response of crustal fl uid to the coseismic stress change. Detailed investigation of the result of stress tensor inversion reveals the existence of local stress fi eld superposed on the regional fi eld represented by the average stress tensor. Inferred local stress fi eld exists in the Tsugaru Strait area, southern part of Akita prefecture, and Kitakami Mountains. |
| Starting Page | 69 |
| Ending Page | 83 |
| Page Count | 15 |
| File Format | PDF HTM / HTML |
| DOI | 10.4294/zisin.65.69 |
| Volume Number | 65 |
| Alternate Webpage(s) | https://www.jstage.jst.go.jp/article/zisin/65/1/65_69/_pdf |
| Alternate Webpage(s) | https://doi.org/10.4294/zisin.65.69 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
