The aftershocks of the Chamoli earthquake (mb 6.3) of 28 March 1999 are analyzed to understand the seismotectonic structure of the Garhwal Himalaya. The permanent as well as temporary microearthquake network data are used. The mainshock occurred on the Basement Thrust by thrust faulting. The aftershocks, on the other hand, are triggered at the seismogenic faults to the south of the Main Central Thrust (MCT) by thrust faulting as well as by strike-slip faulting, and all the events occurred above the plane of detachment/basement thrust. The MCT is not the seismogenic fault.