Northern California utility electric and natural gas infrastructure absorbed a 6.5-magnitude earthquake off the coast of the fishing town of Eureka on Saturday. At its peak 36,000 Pacific Gas and Electric Co. customers were without electricity and/or gas services, but by 8 a.m. Sunday all of them were restored, a PG&E utility spokesperson told NGI.

Centered about 13 miles offshore, the temblor struck about 4:27 p.m. PST, sending many of residents in the town of 26,000 into the streets and many off to nearby higher ground. It triggered memories of years past when major quakes in the area were followed by a tsunami that battered the fishing town and killed up to 11 people in Crescent City, CA, 80 miles to the north near the Oregon border in 1964.

News reports indicated that the extent of the impact was in damage to the electricity grid, but there were also water and gas lines impacted. PG&E’s spokesperson said most of the customer outages were restored overnight, and all were finished by early Sunday.

In addition, PG&E performed a thorough examination of its natural gas-fired generation plant on part of a closed nuclear facility in Humboldt County, determining that no damage was sustained. The power plant, which consists of two 105 MW units and two 15 MW mobile gas-fired generating units, continued to operate at full capacity.

About 10 aftershocks were reported in Sunday’s Los Angeles Times, which quoted a University of California, Berkeley, seismologist as charactering the general Eureka and Humboldt County area as including one of the most seismically active parts of the San Andreas fault system that runs through the length of California. Offshore Eureka is where three major tectonic plates collide, forming what the scientists call the Mendocino Triple Junction (Pacific, North American and Juan de Fuca plates).

The last sizable quakes in the region were 7.2 and 6.6 in magnitude in June 2005, according to the seismologists quoted by the LA Times.

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