Abstract
The investigation of faults and earthquakes in Gonabad region are represent that occurrence of few big earthquakes with high magnitude. The study of historical earthquakes in this area shows the big catastrophic quakes were occurred during the historic period.
More addition the risk analyses were done by definite method,that all of seismic source was distinguished at first.
For this stage prepared a map with 1/500000 of active faults and earthquake foci, of this region. The length of each fault measured and the maximum probability earthquake can be occur by the activity of each fault was calculated. In addition, the distance between Gonabad city and each fault was measured on the map and then the maximum horizontal acceleration calculated for each fault by using the attenuation relation PGA. Results of this study show which an earthquake with 6.4 magnitudes that the maximum horizontal acceleration will be 0.4 in the Gonabad city the if the Behabad fault will be reactive. The Behabad faults 17km length and the shortest distance from Gonabad city to this fault is 3 km.