Three children, who had gone for fishing in river Beki at Kalgasia village in Assam's Barpeta district, were swept into the waters by the mudslide during the first tremor, official sources said.
While Jehirul Nessa (8) drowned, the other two Moidul Islam and Kamala Khatun were rescued and admitted to the hospital.
The first tremor measuring 4.6 on the Richter scale was felt at 6:53 am in Assam and the neighbouring states of Meghalaya, Nagaland, Arunachal Pradesh and Manipur, according to the Regional Seismological Centre in Shillong.
The tremor was located at latitude 26.3 degree North and 92.0 degree East with its epicentre at a depth of 16 km in Assam's Darrang district.
The second quake of moderate intensity measuring 5.0 struck at 2:04 pm at a depth of 10 km at latitude 29.0 degree North and Longitude 95.0 degree East on the India-China border in Arunachal Pradesh, the met centre said.
In Odisha, the tremor occurred at 8:36 am in Puri district with its epicentre at about 40 km from the seismological observatory at Bhubaneswar, the Meteorological Centre said.
The earthquake was felt in Astaran and nearby areas in the district, but no casualty was reported.