ZHANG Liqiong, senior engineer, majors in earthquake prediction and seismic electromagnetism, E-mail: 1002816326@qq.com
By utilizing the method of dominant azimuth of the geoelectric field, an analysis of the dominant azimuth anomaly changes and characteristics was conducted on the geoelectric field data within a 400 km range of the epicenter of the 2023 Jishishan MS6.2 earthquake. The results show that the earliest anomaly before the earthquake occurred at the Guyuan station, which is located at the intersection of the Haiyuan fault and the Liupanshan fault. During the period of the anomaly, the Jingtai station, located in the middle section of the Haiyuan fault, also showed a rapid and significant deflection of the azimuth. The max azimuth α changes at both stations deviated from the normal background value by about 45°, which is considered a medium to short-term anomaly. The last anomaly to appear was at the Dawu station, located in the Bayan Har block, where the azimuth angle α showed a rapid deflection and jump, deviating from the normal background value by about 90°, which is considered a short-term anomaly. The number of three abnormal stations meets the prediction index system of the geoelectric field dominant azimuth. The evolution of the anomaly shows that the anomalies have quasi-synchronous characteristics in terms of appearance, duration, and end time. In terms of the distance from the epicenter, Guyuan station is the farthest, while Jingtai and Dawu stations are closer to the earthquake epicenter. Before the earthquake, due to the internal compression of the plate, the areas where the three geoelectric field stations are located and the surrounding stress compression changes were intense. When rocks were subjected to pressure and fracture, the fracture structure of the rock mass led to significant changes in the dominant azimuth of the geoelectric field in succession. The subsequent end of the three geoelectric fields anomaly after the earthquake also indirectly reflected the process of the gradual recovery of the rock mass fracture structure after stress release, indicating that the data changes of the three stations can truly reflect the changes in the underground medium.
| 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 |