The earthquake occurred in the rugged mountainous areas between the Himalayas and the Hengduan Mountains. The earthquake was located just south of the McMahon Line between India and Tibet, and had devastating effects in both regions. Today this area is claimed as part of Zayü and Mêdog Counties in the Tibet Autonomous Region by China, and as part of Lohit District in Arunachal Pradesh by India. This great earthquake has a calculated magnitude of 8.6 and is regarded as one of the most important since the introduction of seismological observing stations.