6.9 Northern California quake is state’s largest in nearly a decade

Here are some facts about Sunday’s 6.9 magnitude earthquake in Northern California:

Q: How big was this earthquake?

A: It was a major earthquake, larger in magnitude than the destructive 1994 Northridge quake, which was magnitude 6.7. In California the two most recent larger quakes were the 1999 Hector Mine temblor, magnitude 7.1, and the 1992 Landers quake, which was magnitude 7.3. In 2005, there was an offshore quake in Northern California that was magnitude 7.2.

Q: Why didn’t Sunday’s quake do more damage?

A: It was centered in the Pacific Ocean about 50 miles from Eureka. The depth of the quake was about 4 miles. The quake also did not produce tsunamis. In 1964, an 8.8 earthquake in Alaska caused catastrophic damage on the North Coast. That tsunami killed 11 in Crescent City and destroyed the city’s business district. Accounts from the time reported that fuel tanks erupted in flames while cars and trucks washed down city streets, piling up against buildings. A 6.5 quake hit the area in 2010, snapping power lines, toppling chimneys, knocking down traffic signals, shattering windows and prompting the evacuation of at least one apartment building.
Q: Why is this area so seismically active?

A: The North Coast sits along the Mendocino Triple Junction, where three tectonic plates collide: the Pacific, North American and Juan de Fuca. It is one of the most seismically active parts of the San Andreas fault system that runs through the state.

Q: How far was the quake felt?

A: According to the U.S. Geological Survey, the quake was felt over much of Northern California, as far south as San Francisco. It was also felt in southern Oregon. The USGS classified the shaking on land closest to the epicenter as light to moderate, which explains why there was no damage.

Q: How does this quake stack up compared to others?

A: Here are some major California quakes since 1990, courtesy the Associated Press, not including Sunday’s temblor.

1. 7.3, Landers, Calif., June 28, 1992, three deaths
2. 7.2, Cape Mendocino, Calif., April 25, 1992
3. 7.2, Off coast of Northern California, June 15, 2005
4. 7.1, Hector Mine, Calif., Oct. 16, 1999
5. 7.0, Honeydew, Calif., Aug. 17, 1991
6. 7.0, Cape Mendocino, Calif., Sept. 1, 1994
7. 6.7, Northridge, Jan. 17, 1994, 60 deaths
8. 6.6, San Simeon, Calif., Dec. 22, 2003, 2 deaths
9. 6.6, Off coast of Northern California, June 17, 2005
10. 6.2, Joshua Tree, Calif., April 23, 1992