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Outline
We collect the focal mechanisms of M≥3.0 earthquakes in western Yunnan region from 2013 to 2024, use the superimposed stress field method to carry out regional tectonic stress inversion, and investigate the spatiotemporal evolution characteristics of focal mechanism consistency before and after M≥5.0 earthquakes. The results show that the focal mechanism in the study area is mainly slip-type, supplemented by normal fault type. The plunge angles of P-axis and T-axis are small, and the fault plane is mostly high dipping. The stress type in the study area is slip-type. The compressive stress is mainly in the direction of NE to NNE, with a better consistency, while the tension stress is dominant in the direction of SEE. The dip angles of compressive stress and tension stress are small and close to the horizontal in western Yunnan. The study area is mainly characterized by horizontal stress and is subject to horizontal compression in the NE to NNE direction and tension in the SEE direction. The M≥5.0 earthquakes occurred in areas with low variance of stress tensor or their edges, and the stress tensor variance experienced the process of decreasing from the peak before the earthquake. The continuous decrease or low level of stress tensor variance may be closely related to the risk of moderate earthquakes in the western Yunnan, but the relationship between them is not unique, and can be comprehensively analyzed by combining with other parameters, such as the low b-value. The research findings provide a reference for analyzing seismic source characteristics, studying tectonic stress, and tracking seismic activity in the study area.
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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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