Richland — A magnitude-3.2 earthquake was reported north of Richland at 6:47 a.m. Sunday by the U.S. Geological Survey.
Its seismic map puts the earthquake 8 miles north of Richland, close to the magnitude-3.4 earthquake that some Richland residents reported feeling in October 2011.
It is apparently in the same area north of the Richland and near Wooded Island in the Columbia River where about 300 small earthquakes were detected between January and early spring 2009, the largest a magnitude-2.9. Similar swarms were recorded there in 1970, 1975 and 1988.
Pacific Northwest National Laboratory officials said previously that the fault there is about 300 by 300 feet and likely less than a mile deep.
Because of the thickness of the basalt rock layer at that depth, theres a limit to the magnitude of the quakes the fault produces. The USGS reported Sundays earthquake at a depth of about 325 feet below ground.
Of more concern for the Hanford nuclear reservation and Energy Northwests nuclear plant north of Richland are findings in recent years about possible seismic hazards. The active faults of the Puget Sound Region may be connected to the Mid-Columbia by faults that cross the Cascades, Herald columnist Steve Reidel has reported.
The Department of Energy is conducting an assessment to update the last comprehensive look at the earthquake hazard at Hanford, which was conducted in 1996. DOE reported last year that the study would be completed in August 2014.
The Columbia Generating Station nuclear plant was built to withstand a 6.9-magnitude earthquake close to the plant, according to Energy Northwest. To learn more about earthquake risk in the area of the plant, Pacific Northwest National Laboratory has been leading an in-depth study paid for in part by Energy Northwest.