A powerful earthquake struck near the Marianas Islands in the South Pacific, Japan's weather agency said Wednesday, adding that there was no threat of a tsunami.

The Meteorological Agency initially said the quake's magnitude was 7.5 but later revised it to 7.0 after analyzing the data. The U.S. Geological Survey said the magnitude was 7.2.

The quake struck about 12:30 p.m. and occurred at a depth of about 150 miles, the Meteorological Agency said. The agency said the temblor's epicenter was in the northernmost reaches of the island chain.

The islands lie along the Pacific Basin's "Ring of Fire," an arc of volcanos and fault lines where quakes are frequent.