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The earthquake, which struck at 3:50 p.m. local time on Monday, was centered about 20 kilometers southeast of Pinotepa Nacional, according to Mexico's seismological agency SSN. It said the earthquake struck at a shallow depth of 20 kilometers.
SSN initially measured Monday's earthquake at 6.0 before downgrading it to 5.4, but the U.S. Seismological Agency put the magnitude at 5.7.
Details about damage or casualties were not immediately available, but the tremors were felt as far away as Mexico City, where buildings shook and some were evacuated. Because the earthquake struck on land, there is no threat of a tsunami.
Mexico sits on the so-called 'Pacific Ring of Fire', an arc of fault lines circling the Pacific Basin which is prone to frequent and large earthquakes. In late March, a powerful 7.4-magnitude earthquake struck southwestern Mexico, killing at least two people and injuring 11 others.
Comment: The North American Craton, an unbudgeable mass at the center of the continent, experiences an ongoing squeeze play from a) Pacific Plate and N. American Plate subduction activities steadily pushing eastward, and b) the Mid Atlantic Ridge spreading westward. In the middle is the New Madrid Fault Zone. Its last big earthquake was felt from the Rockies to the Atlantic coast, and from the Gulf of Mexico to the Great Lakes. Though the spacing history between eruptions suggests it is not due, given the rapidly increasing PAC-RIM earth changes of late, concern is not unfounded.