U.S. Experts Report Lower Magnitude

The National Earthquake Information Center has lowered official estimates of the magnitude of Tuesday’s earthquake in the Kobe-Osaka region of Japan.

By the scale used most widely in the scientific community in the United States and elsewhere, the quake had a magnitude of 6.8, said Stuart K. Koyangi, a geophysicist at the center, which is operated by the U.S. Geological Survey in Golden, Colo.

The Japanese Meteorological Agency initially reported the Kobe quake as a 7.2 temblor, in part because a slightly different formula was used to calculate the magnitude. The new estimate is also preliminary and may be revised again.

USGS experts use readings from seismic monitoring stations around the world to calculate a temblor’s place on a scale of earthquake strength in which every additional point represents a tenfold increase in power.

Depending on their location, seismic monitoring stations can receive widely varying readings on the same earthquake, because of distance and local geology. Some stations in Japan, for example, reported magnitude readings of 6.9.