DISTRIBUTION OF UNDERGROUND SEISMIC INTENSITY IN THE EPICENTRAL AREA OF THE 1976 TANGSHAN EARTHQUAKE

Based on results of underground observations (in coal mines) in the epicentral area of the 1976 Tangshan Earthquake magnitude 7.8, it can be seen that beneath zones of higher seismic intensity of the area destructions attenuate rapidly with depths exponetially, becoming nearly constant at about 500 m below the surface. The distribution of seismic intensity in the horizental plane underground is controlled by the earthquake generating faults. Seismic intensity attenuates much more rapidly on both sides of a fault than on the surface vertically above.