4.3 Ocean Temblor Occurs Near Eureka

The third moderate earthquake off the Humboldt County coast within the last month occurred Wednesday afternoon and registered magnitude 4.3, the U.S. Geological Survey said.

The quake, which was centered 81 miles southwest of Eureka, occurred at 2:19 p.m., but reportedly was not strong enough to be felt on land.

The quake was in the general area of the geological feature known as the “triple junction,” where the Gorda and North American tectonic plates intersect with the Pacific plate and the northern end of the San Andreas fault.

It happened two miles under the ocean floor.

The temblor was farther out to sea than either a 4.4 quake that was centered 35 miles southwest of Eureka on Aug. 25 or a 5.1 that was centered 76 miles west of Eureka on Aug. 15.

A great many quakes take place in this general area and three moderate ones within a month are not uncommon.

The much more powerful quakes of April 25 and 26, 1992, magnitude 7.1, 6.5 and 6.2, were centered close to shore, and caused 356 injuries and $48 million in damage.

The last damaging quake in the area was a magnitude 5.3 on Dec. 26, 1994, that caused 25 injuries. It was centered 12 miles from Eureka.

Lori Dengler, a geology professor at Humboldt State University, said Wednesday that since 1994, the area has actually been, on the average, seismically quieter than normal.

Records dating back over a century show that the Eureka area suffers a damaging quake on average between every six and seven years, although on one occasion it went 13 years without one, Dengler said.

Eureka records a higher frequency of strong temblors than the Los Angeles area.