To monitor underground environments, the underground radio propagation model can be used by underground wireless signal networks which use the wireless signal strength variation in the soils as the main indicator of an event. By analyzing the received signal strength, the wireless sensor networks can collect additional information from the wireless data carrier.
The targeted events are subserface hazards such as a landslide or earthquake which involve a lot of shifting and moving of earth masses ,and the intrusion of chemical plume which would dramatically change the physical properties of the host soil as shown in the Figure 1 .These events would affect the transmission of radio waves and the received signal strength in the region. Because the underground received signal strength deviation is very small .the subserface events can be detected by the signal strength deviation as follows :