Two jarring earthquakes struck just off the Hermosa Beach coast on Monday, rattling nerves but little else.
First, a jolt measuring 3.6 on the Richter scale struck three-and-a-half miles offshore, and nine miles deep, at 2:17 a.m., followed by three smaller shocks, all of them 2.1 or milder on the Richter scale.
Then at 4:59 p.m., a jarring 3.7 quake struck about four miles offshore, and seven miles deep, followed by three milder shocks, including a 2.7 shaker just north of the Palos Verdes Peninsula.
Authorities reported no damage in Hermosa. Typically, damage to buildings is associated with quakes measuring 4.5 or greater on the Richter scale.
Geophysicists did not associate the quakes with an increase or a decrease in the chances of an imminent, larger earthquake.
Geophysicists also did not determine the specific fault upon which the quakes occurred, but noted that the closest one is the Redondo Canyon Fault, which runs just offshore of the South Bay.
The “swarm pattern” of the tightly clustered earthquakes is common, said John Bellini, a geophysicist with the U.S. Geological Survey.
“California is very active,” he said. “We get swarms all the time.”
The first quake jolted local residents from their sleep.
“It jarred pretty good here, but there were no problems,” said Hermosa Beach Fire Captain James Crawford.
“It shook for about three or four seconds, then there was a large snap,” said Public Works Superintendent Mike Flaherty, who lives in Hermosa. “It rattled all the pictures in the house, I’ll tell you that.”
Within 12 hours of the quake, more than 400 people had logged onto a USGS website to report having felt it. Responses came from all over the greater South Bay, and sections of Los Angeles.
The largest numbers of immediate responses came from the three beach cities. More than 200 responses came from people in Hermosa, nearly 300 came from Manhattan Beach, and more than 500 came from Redondo Beach.
Some outlying responses defied the statistical curve, including one that came from a very light sleeper in Glendale, Ariz., 384 miles from the epicenter.
Within eight hours of the evening quake, more than 3,500 people had reported it to the USGS. Again responses came from all over the greater South Bay and areas of Los Angeles.
More than 160 responses came from Hermosa, more than 200 came from Manhattan and about 400 came from Redondo. ER
