Seismotectonics of the 2018 northern Osaka M6.1 earthquake and its aftershocks: joint movements on strike-slip and reverse faults in inland Japan
Abstract On June 18, 2018, an MJMA6.1 inland crustal earthquake occurred on the northeast edge of the Osaka basin, Japan. This event impacted the region by the maximum PGA larger than 0.9 g, and it was followed by a series of weaker aftershocks. The earthquakes were located near the Arima-Takatsuki...
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| Format: | Article |
| Language: | English |
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SpringerOpen
2019-03-01
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| Series: | Earth, Planets and Space |
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| Online Access: | http://link.springer.com/article/10.1186/s40623-019-1016-8 |
| _version_ | 1819049690529792000 |
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| author | Miroslav Hallo Ivo Opršal Kimiyuki Asano František Gallovič |
| author_facet | Miroslav Hallo Ivo Opršal Kimiyuki Asano František Gallovič |
| author_sort | Miroslav Hallo |
| collection | DOAJ |
| description | Abstract On June 18, 2018, an MJMA6.1 inland crustal earthquake occurred on the northeast edge of the Osaka basin, Japan. This event impacted the region by the maximum PGA larger than 0.9 g, and it was followed by a series of weaker aftershocks. The earthquakes were located near the Arima-Takatsuki Tectonic Line (ENE–WSW dextral strike-slip faults) and the Uemachi fault system (N–S reverse faults), hence the seismotectonic interpretations we assumed to be rather complex. Here we propose a seismotectonic model of this sequence based on seismological data and stress field considerations. In particular, we infer to a centroid moment tensor for the mainshock using Bayesian full-waveform inversion from strong motion records. The solution of Mw5.6 involved a significant CLVD component, which we interpreted as being due to rupture process on a complex fault geometry. Decomposition of the non-DC moment tensor into major and minor pure-shear moment tensors suggests a combination of strike-slip and reverse faulting mechanisms. We also analyzed the 108 strongest aftershocks with MJMA between 2.0 and 4.1 using records from broadband and short-period stations. Aftershocks’ moment tensors inverted from P-wave amplitudes exhibit mainly strike-slip and reverse faulting mechanisms, having significant spatial variations. The local stress field inverted from these mechanisms had a dominant maximum (compressional) principal stress σ 1 in ESE–WNW direction, while σ 2 ≅ σ 3. Both ENE–WSW dextral strike-slip and N–S reverse faults can be active in such stress field as observed in the mainshock (without any need for stress spatial inhomogeneity). To conclude, the activated strike-slip fault is parallel to the Arima-Takatsuki Tectonic Line. The activated N–S reverse fault is dipping to east by 50° similarly as the Uemachi fault system. Joint shear movements on both of these faults contributed significantly to the total seismic moment of the mainshock. |
| first_indexed | 2024-12-21T11:36:10Z |
| format | Article |
| id | doaj.art-36b75b339a984a2f875a950153c6cdba |
| institution | Directory Open Access Journal |
| issn | 1880-5981 |
| language | English |
| last_indexed | 2024-12-21T11:36:10Z |
| publishDate | 2019-03-01 |
| publisher | SpringerOpen |
| record_format | Article |
| series | Earth, Planets and Space |
| spelling | doaj.art-36b75b339a984a2f875a950153c6cdba2022-12-21T19:05:27ZengSpringerOpenEarth, Planets and Space1880-59812019-03-0171112110.1186/s40623-019-1016-8Seismotectonics of the 2018 northern Osaka M6.1 earthquake and its aftershocks: joint movements on strike-slip and reverse faults in inland JapanMiroslav Hallo0Ivo Opršal1Kimiyuki Asano2František Gallovič3Faculty of Mathematics and Physics, Charles UniversityThe Institute of Technology and Business in České BudějoviceDisaster Prevention Research Institute, Kyoto UniversityFaculty of Mathematics and Physics, Charles UniversityAbstract On June 18, 2018, an MJMA6.1 inland crustal earthquake occurred on the northeast edge of the Osaka basin, Japan. This event impacted the region by the maximum PGA larger than 0.9 g, and it was followed by a series of weaker aftershocks. The earthquakes were located near the Arima-Takatsuki Tectonic Line (ENE–WSW dextral strike-slip faults) and the Uemachi fault system (N–S reverse faults), hence the seismotectonic interpretations we assumed to be rather complex. Here we propose a seismotectonic model of this sequence based on seismological data and stress field considerations. In particular, we infer to a centroid moment tensor for the mainshock using Bayesian full-waveform inversion from strong motion records. The solution of Mw5.6 involved a significant CLVD component, which we interpreted as being due to rupture process on a complex fault geometry. Decomposition of the non-DC moment tensor into major and minor pure-shear moment tensors suggests a combination of strike-slip and reverse faulting mechanisms. We also analyzed the 108 strongest aftershocks with MJMA between 2.0 and 4.1 using records from broadband and short-period stations. Aftershocks’ moment tensors inverted from P-wave amplitudes exhibit mainly strike-slip and reverse faulting mechanisms, having significant spatial variations. The local stress field inverted from these mechanisms had a dominant maximum (compressional) principal stress σ 1 in ESE–WNW direction, while σ 2 ≅ σ 3. Both ENE–WSW dextral strike-slip and N–S reverse faults can be active in such stress field as observed in the mainshock (without any need for stress spatial inhomogeneity). To conclude, the activated strike-slip fault is parallel to the Arima-Takatsuki Tectonic Line. The activated N–S reverse fault is dipping to east by 50° similarly as the Uemachi fault system. Joint shear movements on both of these faults contributed significantly to the total seismic moment of the mainshock.http://link.springer.com/article/10.1186/s40623-019-1016-8SeismotectonicsOsakaTakatsukiEarthquake sourceBayesian inversionMoment tensor |
| spellingShingle | Miroslav Hallo Ivo Opršal Kimiyuki Asano František Gallovič Seismotectonics of the 2018 northern Osaka M6.1 earthquake and its aftershocks: joint movements on strike-slip and reverse faults in inland Japan Earth, Planets and Space Seismotectonics Osaka Takatsuki Earthquake source Bayesian inversion Moment tensor |
| title | Seismotectonics of the 2018 northern Osaka M6.1 earthquake and its aftershocks: joint movements on strike-slip and reverse faults in inland Japan |
| title_full | Seismotectonics of the 2018 northern Osaka M6.1 earthquake and its aftershocks: joint movements on strike-slip and reverse faults in inland Japan |
| title_fullStr | Seismotectonics of the 2018 northern Osaka M6.1 earthquake and its aftershocks: joint movements on strike-slip and reverse faults in inland Japan |
| title_full_unstemmed | Seismotectonics of the 2018 northern Osaka M6.1 earthquake and its aftershocks: joint movements on strike-slip and reverse faults in inland Japan |
| title_short | Seismotectonics of the 2018 northern Osaka M6.1 earthquake and its aftershocks: joint movements on strike-slip and reverse faults in inland Japan |
| title_sort | seismotectonics of the 2018 northern osaka m6 1 earthquake and its aftershocks joint movements on strike slip and reverse faults in inland japan |
| topic | Seismotectonics Osaka Takatsuki Earthquake source Bayesian inversion Moment tensor |
| url | http://link.springer.com/article/10.1186/s40623-019-1016-8 |
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