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By Haidee V. Eugenio

SAIPAN, CNMI (Marianas Variety, Nov. 5) –Four separate earthquakes measuring 4.7 to 6.0 magnitude on the Richter scale hit the Marianas on Wednesday, but none resulted in damage or injuries.

The quakes occurred in just a five-hour period, starting with an intensity 4.7 quake at 2:44 p.m.

Data from the U.S. Geological Survey’s National Earthquake Information Center showed that the quakes’ epicenters were between Saipan and Rota.

However, based on NEIC data, the quakes were all nearer to Saipan than Rota.

The epicenter of the first quake was located 95 miles east-southeast of Saipan and 115 east-northeast of Rota, at a depth of 18.5 kilometers from the surface.

The second tremor – this time an intensity 6 – hit at 6:31 p.m. at a depth of 10 km.

The epicenter was located 85 miles east-southeast of Saipan, 110 miles east-northeast of Rota and 155 miles east-northeast of Hagåtña, Guam.

This was followed by a 4.9 magnitude temblor at 6:39 p.m., occurring also at a depth of 10 km. and whose epicenter was at 100 miles southeast of Saipan and 115 miles east of Rota.

The fourth quake, measuring 5.2 on the Richter scale, struck at 7:27 p.m., also at a depth of 10 km.

Its epicenter was located 90 miles southeast of Saipan and 110 miles east-northeast of Rota.

The quakes occurred a few months after the USGS presented to lawmakers the planned study on underwater volcanic activity in Rota, after scientists discovered hydrothermal systems or plumes being emitted underwater.

Chong said there are more underwater volcanoes in the Marianas than above water volcanoes.

He said this volcanic activity may be related to the quakes that occurred on Wednesday, adding that EMO will immediately confer with USGS on these matters.

In October, a number of quakes also occurred in the Marianas region – ranging from intensity 4.9 to 6. None of these quakes generated tsunami watches or warnings, said Chong.

The CNMI sits on the Philippine sea plate of a seismically active region known as the "Ring of Fire" that is being pushed up by the Pacific sea plate.

The last major quake to hit Marianas was in Oct. 2001. It measured 7 on the Richter scale and resulted in major damage to property.

November 5, 2004

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