Zahra SARIHI - Student, IIEES, Tehran, Iran
Mehdi ZARE - Professor, IIEES, Tehran, Iran

Considering seismicity and earthquake hazard is important in a high seismic area. Studying the aftershocks is important from different aspects; for instance, the impact of aftershocks on the structures damaged in the earthquake from the one hand, and the disturbance caused in the rescue process from the other hand (Hough & Jones, 1997).The importance of study the distribution of aftershocks can be used to estimate the amount of energy release in most seismic zones, the seismic zones, length of the activate faults and the process of migration of aftershocks (Ogata & Shimazaki, 1984). The main purpose of this study is to study the probability for strong aftershocks or larger mainshocks for Kermanshah zone using the Reasenberg-Jones relation (Reasenberg & Jones, 1989). To this end, the catalogue of the Kermanshah earthquakes between 2017/11/12 and 2019/03/16 has been collected and homogenized among which five earthquakes have been selected to study their aftershock decay rates. Catalogue of aftershocks has been collected, based on the distribution of the aftershocks and the fault trajectories of each earthquake. The Gutenberg-Richter diagram has been plotted separately for each earthquakes, and the variables A, b, and Mc has been obtained for each seismic zone (Table 1). The next step, modify the catalogue and remove smallerearthquakes from the Mc, and then the modified Omori law has been applied to the new catalogue and the variables P, C and K has been calculated (Table 1) (Ogata, 1983). By placing the variables in Equation 1, the probability for strong aftershocks or larger mainshocks has been calculated for Kermanshah zone (Table 2) (Reasenberg & Jones, 1989; Lolli & Gasperini, 2003; Ommi et al., 2016).

Earthquake prediction, Aftershock decay rate, Modified Omori law, Gutenberg-Richter, The risk of aftershock