The event occurred about one-and-half hours after the plane's last definitive sighting on civilian radar March 8, Xinhua reported, citing a research group on seismology and physics of the earth's interior under the University of Science and Technology of China.
The area, 116 km northeast from where the last contact with the plane was recorded, used to be a non-seismic region, the group said.
Malaysia Airlines flight MH370 with 239 passengers and crew on board vanished without any trace about an hour after taking off from Kuala Lumpur early March 8. The Boeing 777-200ER was presumed to have crashed off the Vietnamese coast in the South China Sea.
The plane took off from Kuala Lumpur at 12.41 a.m. on March 8 and was due to land in Beijing at 6.30 a.m. the same day. The 227 passengers on the flight included five Indians, 154 Chinese and 38 Malaysians.
Contact with the plane was lost along with its radar signal at 1.40 a.m on March 8 when it was flying over the Ho Chi Minh City air traffic control area in Vietnam.
"The seafloor event could have been caused by the plane possibly plunging into the sea," the Chinese university research group said on Friday.
The location of the event was identified based on records of two seismographs located in Malaysia.
If the data is proved to be linked to the missing flight, "the strength of the earthquake wave indicates the plunge was catastrophic", according to the research group.
Meanwhile, dozens of ships and planes from around 10 countries are scouring the waters around flight MH370's last known location, but no solid clues have been found so far.
In an update on its website on Friday morning, Malaysia Airlines said though it was fully aware of various ongoing media speculations, it had "nothing further to add to the information" they have already provided.
The airline reiterated it "will continue to give full support in cooperating with the search and rescue mission, which is coordinated by the Department of Civil Aviation Malaysia (DCA) under the purview of the Ministry of Transport, Malaysia".
It also promised to continue to provide regular updates to the public on all matters affecting flight MH370.
The Malaysian company stressed that its focus at this point in time was to care for the families of the passengers and crew of flight MH370, which means providing them with timely information, travel facilities, accommodation, meals, medical and emotional support.
As the search expands to include the Indian Ocean, Malaysian authorities and the airline itself have continued to deny reports that the missing plane might have continued flying for some time after last contact.
Meanwhile, Vietnam extended its sea search operations to two new areas off the southern coast on Friday, local officials revealed.