Full
DUAN Meifang, engineer, majors in focal mechanism and stress field, E-mail: duanmeifangfang@163.com
Outline
Using the FOCMEC method, we calculated the focal mechanism of 89 earthquakes with magnitude between 2 and 3.5(2≤ML≤3.5) in the middle and southern section of Weixi-Qiaogou fault and its surrounding areas(99.5°-100.5°E, 25.0°-26.5°N) from 2018 to 2022. Combining with the collected focal mechanism results of 132 earthquakes with magnitude greater than 3.5(ML > 3.5), we inverted the regional stress using the tensor damping method to obtain a detailed tectonic stress field with a resolution of 0.25°×0.25° of the study area. We analyzed the distribution characteristics of focal mechanism solutions and stress field, and discussed the stress state of the middle and southern section of Weixi-Qiaogou fault and its surrounding areas. The results show: 1) The types of earthquake focal mechanisms in the study area are mainly strike-slip, followed by normal fault type. 2) The study area is subjected to NS-directed compression and EW-directed extension, with the overall principal compressive stress orientation being NNW-SSE, showing a clockwise rotation trend. The stress tensor factor R value varies between 0.02 and 0.39, indicating that the study area is generally characterized by compressive stress. 3) The stress field direction of Jianchuan-Dali section of Weixi-Qiaohou fault is mainly NNW-SSE, with a small amount of nearly NS direction, and the stress field is mostly horizontal, with a smaller R value. The Dali-Weishan section has a stress field direction of NNE-SSW and NS, and the stress field is mainly vertical, with a larger R value.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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