Behavior of Aftershocks of Gorkha Nepal Earthquake of 2015

After any large earthquake, people are scared of aftershocks and wish to know that how long the aftershocks may continue and what could be the maximum magnitude. The behavior may be somewhat different in different regions; hence, it is important to study the same for the Gorkha Nepal earthquake. Generally, it has been observed that the largest aftershock may have one unit less than the mainshock. However, in the case of the Gorkha earthquake, the difference is only 0.5 units. It may be due to the fact that the largest aftershock had an independent but contiguous rupture zone. The duration of aftershocks is longer than expected for the region. Rupture of Nepal April 2015 earthquake of Mw 7.8 in Eastern Nepal occurred along the Main Himalayan thrust (MHT) and that of May 12 major earthquake was NE of it. Adhikari et al. (2015) presented the temporal and spatial distribution of aftershock activity that occurred for the first 3 months by using the data of the Nepal seismic network. Baillard et al. (2017) processed the same data with automatic onset and hypocenter determination procedures and stated that most aftershocks are in the Main Central Thrust zone and the May 12 Mw 7.3 earthquake had its own aftershock activity. Yamada et al. (2019) studied the aftershocks for an 11-month duration obtained with additional local seismograph stations. Results of Rastogi and Mittal (2016) on the investigation of aftershock behavior of the two major 2015 earthquakes using the EMSC catalog of M ≥ 4 earthquakes until September 2015 are presented here. The aftershock behavior of the two major earthquakes is compared with each other and also with the total distribution. Time and space variation as well as the “b” value (ratio of smaller to larger earthquakes) and “p” value rate of decay of aftershocks)Rate of decay of aftershocks were investigated.