The Chinese Xinhua news agency is now throwing up another possibility. They claim that a Chinese research group on seismology and physics of the earth's interior, detected a "sea floor event" at 2:55AM local time (doesn't say whether Vietnamese or Malaysian local time, but we'll presume Vietnamese) that threw up an "earthquake wave".
They claim it could have been MH370 hitting the sea in that spot - which spot has been claimed to be 116km NW of the last recorded location of the aircraft. The area is reputed to be normally "non-seismic".
"Seafloor event" possibly linked to MH370: Chinese researchers - Xinhua | English.news.cn
My opinion? A possibility, but unlikely. After nearly 7 days of SAR work, plus wind and wave action, surely some debris would have been found in this area of the Gulf of Thailand, by fisherman at least.
There is a world earthquake map, showing earthquakes over the last 7 days - but only magnitude 4.5 and greater.
A B777 hitting the water wouldn't produce anything near a 4.5 magnitude measurement, but it would likely be recorded as a verifiable tremor.
http://earthquakestoday.info/