SHORT-PERIOD GEOMAGNETIC VARIATION ANOMALY IN YUNNAN PROVINCE

Yunnan Province is situated at the southern end of the North-South Seismic Belt of China. This area bounded on the west by the Xizang Plateau, with very intense recent tectonic movements and high seismic activity, consists of very complicated crustal structures.Geomagnetic data observed at nine stations in Yunnan Province were collected and preliminarily analysed. Results obtained show that short-period geomagnetic variation anomaly does exist. There is a northwest-southeast demarcation line, starting from li Jiang on the northwest, southeastward to XiaGuan, ChuXong and Tong Hai of the province. △Z (Changes in the Vertical field) for the sudden storm commencements and geomagnetic bays to the northeast and southwest of this line appear opposite in signs. It is therefore inferred that a northwest-southeast belt of high conductivity exists underneath Yunnan Province.Finally, other geophysical phenomena related to this high conductivity belt were discussed briefly.