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Magnitude 5.2 Earthquake Hits Anza-Borrego Area

Magnitude 5.2 Earthquake Hits Anza-Borrego Area
Magnitude 5.2 Earthquake Hits Anza-Borrego Area GUEST: Thomas Rockwell, earthquake geologist, San Diego State University

I'm Tom Fudge. Thank God, it's Friday, June 10. Our top story, last night the ground shook in San Diego, you may have slept through it. I woke up when it happened at 1:05. It was just North of Borrego Springs and it was five It was just North of Borrego Springs and it was 5.2 on the Richter scale. Joining me to tell us more is Tom Rockwall a seismologist at San Diego state. Thank you for coming in. Whose fault was this? I love asking that question. This occurred on the main strand of these Sanders sit still fault -- San Jacinto fault. Tell us about the San Jacinto fault and what kind of a fault is it. It is basically the Western strand of the San Andreas Fault. It has a similar strain it accumulation rate. Every two or 300 years we can expect a very large earthquake. At the past 100 years, have we had some big faults on that line? There have been a number of earthquakes in the magnitude 6 range. In this region, there's been a number of?. There have been moderate earthquakes. The last really big one, was November 22, 1700, it was historically recorded. That was about a 7.3. While. The earthquake last night, has been described as a shallow earthquake. What does that mean? Put that into context of other earthquakes. All earthquakes are shallow, the crust in Southern California is only seismic down to 15 km. We can only have deeper earthquakes in areas like subduction zones, we do have those off of northern California, Oregon and Washington. They can get as deep as 600 km. When they talk about shallow earthquakes, they are talking less than 20 km. That incorporates all of Southern California. Even when you get a big one in California, it's shallow by definition, because that's the geology of our area? Even when the San Andreas goes it will only rupture to 15 km. The last time on the San Jacinto fault that we got a big one, that was the 18th-century? Yes November 1800. It's been 216 years since the last earthquake. Does that mean we are doing? We are coming into the window, where we worry about magnitude 5's as being for shots. We are not out of the window that that could have been a for shock. Speaking of four shocks, did we have any aftershocks? We have had 450 We have had 452 this point. 450? Yes. It may or may not be a higher being there of a larger earthquake. Yes. There's a 5% chance that in the next 48 hours that will be followed by a larger earthquake. That means 95% chance that it won't, and everyone should be prepared. Joining me has been Tom Rockwell, a seismologist at San Diego state. Thank you very much. You're welcome, thank you.

A strong and very shallow earthquake struck early Friday in the Anza-Borrego Desert State Park in northern San Diego County, followed by several aftershocks, the U.S. Geological Survey reported.

The temblor struck at 1:04 a.m. at a depth of 0.6 of a mile with a magnitude of 5.2, according to the USGS.

A quake of such strength can generate considerable damage, but there were no immediate reports of injuries or damage in San Diego or Riverside counties, and no threat of a tsunami, authorities said.


"We did not have any reports of damage or injuries from earthquake," San Diego Police Chief Shelley Zimmerman said, adding: "This is a good reminder to have a plan in place."

However, the earthquake triggered a minor rockslide on Montezuma Valley Road, about 14 miles southeast of Borrego Springs. California Highway Patrol officers worked to clear the road, the CHP reported.

The quake's epicenter was 13 miles north-northwest of Borrego Springs in San Diego County and 16 miles south-southwest of La Quinta in Riverside County. It was strong enough to be felt in Los Angeles, as well as in San Bernardino and Orange counties and in parts of Mexico.

The earthquake occurred along the San Jacinto Fault, historically the most active fault in Southern California, said seismologist Lucy Jones. It was near a magnitude 6 earthquake in 1937 and a magnitude 5.3 earthquake in 1980, Jones reported.

"We have never seen a San Andreas earthquake triggered by a San Jacinto earthquake," Jones wrote on Twitter, referring to the state's most famous fault, the one along which the so-called "big one" is expected to hit someday.


"Every earthquake has a 5 percent of triggering an aftershock that is bigger than itself — always within a few miles of location of the first earthquake," Jones wrote.

There were at least eight aftershocks in the same general area within 3 hours and 10 minutes. The strongest were magnitude 3.5 shakers at 1:06 a.m., 1:33 a.m. and 4.14 a.m. — all at a depth of slightly more than 6 miles.

Cathy Gaffney, manager of the Hacienda del Sol inn in Borrego Springs, said she woke up when the quake hit.

"It's definitely something that starts your heart up at one in the morning," she said. Gaffney said the quake felt similar to the one centered in Mexicali that hit on Easter Sunday 2010.

She said there was no damage at the inn, but a few things did fall off the shelves.

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