5. Conclusions
On 25 April, 2015 a southward slip on about 160 km 115 km portion of MBT resulted in the devastating earthquake of Mw7.8 (E1) in Nepal and the largest aftershock of Mw7.3 (E2) on 12 May, 2015 and killed thousands of human lives and left many injured and homeless. GPS stations DNGD, GRHI and RMTE situated south of MBT have moved in the northeast direction and among these three stations RMTE has experienced the maximum offset of 12.3 ± 2.0 mm towards ENE. while station CHLM located in the higher Himalayas north of MBT has been offset by 1.41 ± 0.4 m southward due to E1. The co-seismic offset of GPS stations due to E2 alone are not remarkable.
The main shock of 25 April was followed by about 256 aftershocks resulting from the failure to sustain the positive Coulomb stress change imparted at various depths due to the main event. The locations of greater number of aftershocks at 10 km depth are consistent with the Coulomb stress change imparted at depth of 10 km on a fault plane with strike ¼ 295, dip ¼ 10 and rake ¼ 108. The locations of aftershocks of magnitude >5 including the largest event of Mw7.3 on 12 May, 2015 (E2) are consistent with Coulomb stress change imparted on a fault plane with strike ¼ 305, dip ¼ 9 and rake ¼ 90 at depth of 15 km. The aftershock of Mw6.7 at depth 22 km which occurred on 26, April, 2015 agrees well with the CSC estimated at that depth. But the stress increase that resulted from the E1 event has not been released totally through aftershocks. The main shock E1 has resulted in generating positive CSC at depths 10 km, 15 km and 22 km in the bordering parts of the fault plane without any aftershock occurring there. The accumulating stress will probably be released in the coming decades. Therefore these regions of enhanced CSC should be treated as future threats for the people of Nepal.
