An earthquake of 5.1 magnitude struck the Upper Siang district of Arunachal Pradesh early Thursday, according to the National Center for Seismology (NCS).No immediate loss of life or damage to property was reported, officials said. The mainshock was preceded by a sequence of three minor foreshocks starting in the early hours of Thursday. A shallow tremor of magnitude 2.8 hit the region at 3:40 am at a depth of 5 km, followed closely by a magnitude 3.2 quake at 3:55 am and another magnitude 2.8 event at 4:34 am, it said. Following the main tremor, a magnitude 3.5 aftershock was recorded at 7:17 am at a depth of 5 km, completing a multi-hour seismic swarm. Arunachal Pradesh and the wider Northeast region fall under Seismic Zone-V, making the area highly susceptible to tectonic activity due to the complex fault systems under the Eastern Himalayas.