Northeast India has been subjected to extensive compressional forces, mainly in north–south and east–west directions resulting from the convergence of the Indian plate with the Eurasian and Burmese plates, respectively. The area is characterized as one of the most seismically active regions of the world; however, the lower Assam valley’s microseismicity has not been monitored and studied intensively by a dense seismic network during the past. During this study, a seismic network of 76 stations was deployed in northeastern India for one year. Hundreds of microearthquakes were recorded. The most accurately located events, moment tensor solutions, and focal mechanisms were used in order to define the seismotectonic and stress regime in the area.