The electromagnetic radiation anomalous course of a group of shallow-focus earthquakes

Generally, an Ms 4.0 earthquake makes no damage, but on July 20, 1995 a skin depth's shallow-focus earthquake took place in Xingyuan village in Zhuolu County, and made obvious damages. The Huailai observation station of Hebei earthquake electromagnetic network 16 km from the focus received an obvious electromagnetic radiation abnormal forewarning of the pre-earthquake. The information showed a changing process, which was from weak to strong and from strong to weak and disappeared. And the abnormal characters of direction and frequency changes correlated to the earthquake reappeared.