Present-Day Tectonic Stress Evolution in Southern Yunnan Based on Focal Mechanisms
Tectonic extrusion bypassing the eastern Himalayan syntaxis results in a significant increase in regional stress instability and the associated frequent occurrence of earthquakes in southern Yunnan, China. However, the stress field, and the relationship between the focal mechanism of earthquakes and...
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MDPI AG
2023-08-01
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| Series: | Sensors |
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| Online Access: | https://www.mdpi.com/1424-8220/23/17/7406 |
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| author | Wenjie Fan Ye Zhu Yingfeng Ji Lili Feng Weiling Zhu Rui Qu |
| author_facet | Wenjie Fan Ye Zhu Yingfeng Ji Lili Feng Weiling Zhu Rui Qu |
| author_sort | Wenjie Fan |
| collection | DOAJ |
| description | Tectonic extrusion bypassing the eastern Himalayan syntaxis results in a significant increase in regional stress instability and the associated frequent occurrence of earthquakes in southern Yunnan, China. However, the stress field, and the relationship between the focal mechanism of earthquakes and stress evolution in southern Yunnan, remain enigmatic. In this paper, using a modified grid point test method, we calculated the focal mechanism of <i>M</i><sub>L</sub> ≥ 2.5 earthquakes in southern Yunnan (22–25° N, 100–104° E) from January 2009 to June 2023. Utilizing the solutions of historical earthquake focal mechanisms, we obtained the present-day regional tectonic stress field in southern Yunnan via inversion. The results indicate complex and diverse seismic focal mechanisms, and the main types of earthquakes are strike-slip events, followed by normal fault and reverse fault events. The orientations of the maximum and minimum principal stress axes rotate in a clockwise direction from northeast to southwest. The internal stress orientation distribution of the rhombic Sichuan–Yunnan block in the study area is consistent, and the block boundary zone is the site where stress deflection occurs, and the regional tectonic stress field is influenced by the interaction among different blocks. The distribution of <i>R</i>-value in the Lamping–Simao block gradually increases from north to south, indicating that the compressive stress required for material transport becomes relatively small. Combined with the geological and tectonic background of the study area, our results suggest that the speed of block movement gradually decreases from north to south; the distribution of <i>R</i>-value in the South China block is significantly smaller than that of the interior of the Sichuan–Yunnan rhombus, and the proportion of compressive stresses is larger, indicating a stronger extrusion in this region, which may be related to the fact that the Sichuan–Yunnan rhombus is strongly resisted by the South China block in the east. |
| first_indexed | 2024-03-10T23:13:08Z |
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| issn | 1424-8220 |
| language | English |
| last_indexed | 2024-03-10T23:13:08Z |
| publishDate | 2023-08-01 |
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| record_format | Article |
| series | Sensors |
| spelling | doaj.art-2e1af64e14c04602ad98b0ca570cd8322023-11-19T08:49:28ZengMDPI AGSensors1424-82202023-08-012317740610.3390/s23177406Present-Day Tectonic Stress Evolution in Southern Yunnan Based on Focal MechanismsWenjie Fan0Ye Zhu1Yingfeng Ji2Lili Feng3Weiling Zhu4Rui Qu5State Key Laboratory of the Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, ChinaState Key Laboratory of the Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, ChinaState Key Laboratory of the Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, ChinaQinghai Earthquake Agency, Xining 810001, ChinaState Key Laboratory of the Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, ChinaState Key Laboratory of the Tibetan Plateau Earth System, Environment and Resources (TPESER), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, ChinaTectonic extrusion bypassing the eastern Himalayan syntaxis results in a significant increase in regional stress instability and the associated frequent occurrence of earthquakes in southern Yunnan, China. However, the stress field, and the relationship between the focal mechanism of earthquakes and stress evolution in southern Yunnan, remain enigmatic. In this paper, using a modified grid point test method, we calculated the focal mechanism of <i>M</i><sub>L</sub> ≥ 2.5 earthquakes in southern Yunnan (22–25° N, 100–104° E) from January 2009 to June 2023. Utilizing the solutions of historical earthquake focal mechanisms, we obtained the present-day regional tectonic stress field in southern Yunnan via inversion. The results indicate complex and diverse seismic focal mechanisms, and the main types of earthquakes are strike-slip events, followed by normal fault and reverse fault events. The orientations of the maximum and minimum principal stress axes rotate in a clockwise direction from northeast to southwest. The internal stress orientation distribution of the rhombic Sichuan–Yunnan block in the study area is consistent, and the block boundary zone is the site where stress deflection occurs, and the regional tectonic stress field is influenced by the interaction among different blocks. The distribution of <i>R</i>-value in the Lamping–Simao block gradually increases from north to south, indicating that the compressive stress required for material transport becomes relatively small. Combined with the geological and tectonic background of the study area, our results suggest that the speed of block movement gradually decreases from north to south; the distribution of <i>R</i>-value in the South China block is significantly smaller than that of the interior of the Sichuan–Yunnan rhombus, and the proportion of compressive stresses is larger, indicating a stronger extrusion in this region, which may be related to the fact that the Sichuan–Yunnan rhombus is strongly resisted by the South China block in the east.https://www.mdpi.com/1424-8220/23/17/7406grid point test methodfocal mechanism solutionstress fieldstress shape ratio (<i>R</i>-value)southern Yunnan region |
| spellingShingle | Wenjie Fan Ye Zhu Yingfeng Ji Lili Feng Weiling Zhu Rui Qu Present-Day Tectonic Stress Evolution in Southern Yunnan Based on Focal Mechanisms Sensors grid point test method focal mechanism solution stress field stress shape ratio (<i>R</i>-value) southern Yunnan region |
| title | Present-Day Tectonic Stress Evolution in Southern Yunnan Based on Focal Mechanisms |
| title_full | Present-Day Tectonic Stress Evolution in Southern Yunnan Based on Focal Mechanisms |
| title_fullStr | Present-Day Tectonic Stress Evolution in Southern Yunnan Based on Focal Mechanisms |
| title_full_unstemmed | Present-Day Tectonic Stress Evolution in Southern Yunnan Based on Focal Mechanisms |
| title_short | Present-Day Tectonic Stress Evolution in Southern Yunnan Based on Focal Mechanisms |
| title_sort | present day tectonic stress evolution in southern yunnan based on focal mechanisms |
| topic | grid point test method focal mechanism solution stress field stress shape ratio (<i>R</i>-value) southern Yunnan region |
| url | https://www.mdpi.com/1424-8220/23/17/7406 |
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