UPDATE 4-Second tremor hit Western Mexico
* Two tremors within hours strike Mexico
* Two earlier quakes within the past month
* No tsunami warning (Adds new tremor)
MEXICO CITY, April 12 (Reuters) - Two large earthquakes struck western Mexico, shaking buildings as far away as the capital and sending people rushing out of offices onto the streets, the U.S. Geological Survey said.
There were no reports of major damage after the first of the two tremors.
The USGS said the first quake on Wednesday evening in the western state of Michoacan had a magnitude of 6.5 -- and was recorded at a depth of 12.4 miles.
The second quake, in the early hours of Thursday off Baja California, was stronger at a magnitude of 6.9 and shallower at a depth of 6.2 miles.
Mexico City Mayor Marcelo Ebrard, writing on his Twitter account after the first quake, said there were no initial signs of serious damage. Key services in the capital, including its subway system and the international airport, were operating normally.
"There was a nasty crunching sound in my bathroom and everything moved," said Adela Arceo, who was looking after two young children in the central Roma neighborhood of Mexico City.
There were no initial reports of casualties.
Emergency services in Michoacan and in the neighboring state of Guerrero, which has been hit by a series of recent quakes, reported no major problems on Wednesday.
"You could feel it, but there's no major damage. There are no reports, no emergency calls," said Agustin Lule, a spokesman for fire services in Uruapan, a town in Michoacan near the epicenter.
Reuters reporters in coastal areas of Guerrero and neighboring Oaxaca state said there was no damage.
The Honolulu-based Pacific Tsunami Warning Center said it had issued no tsunami warning, but staff oceanographer David Walsh noted the quake was close to water, big enough and potentially deep enough to cause one.
The two quakes followed two tremors that jolted Mexico within the past month. A 7.4 magnitude quake struck on March 20, damaging hundreds of buildings in the southwest. That was followed by dozens of aftershocks.
Earlier on Wednesday, an 8.7 magnitude earthquake struck off Indonesia, raising fears of a huge tsunami like the one that battered the Indian Ocean rim in 2004, but authorities said there were no reports suggesting a major threat. (Additional reporting by Mica Rosenberg, Simon Gardner, Krista Hughes and Ana Isabel Martinez; writing by Dave Graham; editing by Ron Popeski)