While the rest of the country was gently gearing up for the nation’s Independence Day celebration on Thursday, July 4, a strong earthquake rocked a large swath of Southern California and parts of Nevada in the morning and then again on Friday evening. Both quakes were felt strongly in Ridgecrest, California, near the epicenter as US Geological Survey Seismologist Lucy Jones reported to the press on Thursday.
Jones said, “So the basics of the earthquake: the earthquake is near China Lake and Ridgecrest. So the area to the east of the southernmost part of the San Andreas Fault. The nearest fault is the Little Lake fault and it might be associated with it. But we don’t know.”
A 6.4 magnitude quake struck at 10:33 a.m. Thursday in the Mojave Desert, about 150 miles northeast of Los Angeles and was the strongest quake to hit the region in 20 years until the 7.1 quake happened just after 8 p.m. Friday evening. Jones predicted many aftershocks and said its unusual that the big Thursday quake was preceded by a magnitude 4.2 temblor about a half-hour earlier.
Jones said, “We should be expecting lots of aftershocks and some of them will be bigger than the 3s that we’ve been having so far. We have never seen a foreshock more than 10 kilometers (6 miles) away from its main shock. And this is substantially farther than that to the San Andreas or to the Garlock fault which is another large fault capable of big earthquakes.”
As predicted, one aftershock shook a Ridgecrest press conference on Thursday and Jones explained that people should always prepare for a big quake and that Southern California had actually just experienced a 20-year period of relatively mild earthquakes.
Ridgecrest Police Chief Jed McLaughlin said, “Well, at 10:33 this morning, July 4th, Ridgecrest and the Indian Wells Valley was shaken with a, what’s reported as a 6.4 earthquake. The events that followed that earthquake for the police department, and I’ll let fire talk about their response. We were inundated with calls, with fires and obviously stores that were shaken with stuff falling off shelves.” And then while an aftershock was happening, he said, “We started doing a grid search of streets looking for damage. It’s an earthquake, another earthquake, aftershock. That was an earthquake. So obviously we needed to check for structures that may be down and look for victims that may be trapped.”
Jones said, “One should always be preparing for a big one. This does not make it less likely. There is about a one in 20 chance that this location will be having an even bigger earthquake within the next few days that we have not yet seen the biggest earthquake of the sequence. It’s certain that this area is going to be shaken a lot today and some of those aftershocks will probably exceed magnitude 5, which means they will become damaging. This would be a good time to remind you that if you have been experiencing earthquakes for the last 20 years in Southern California you have been experiencing an extremely quiet time in California history. The last time we had an earthquake in Southern California above magnitude 6 was 1999. The previous decade had had about eight magnitude sixes. So this has been an extremely quiet abnormal time. This type of earthquake is much more normal.”
And then on Friday evening the same area was hit with a second quake of even greater magnitude as Jones explained the difference between intensity and magnitude followed by California Governor’s Office of Emergency Services Director Mark Ghilarducci summarizing the situation and requesting federal assistance.
Jones said, “Notice that there’s red areas. That’s implying quite high shaking intensity. Intensity is different than magnitude. There’s one number to represent the size of the earthquake. Yesterday, the biggest was a 6.4. Today the biggest is a 7.1. Intensity is what you feel. So we have here a map of what the shaking intensities were up around the Ridgecrest area. Notice that they are going into red. That is intensity 9. The 6.4 we only got up into Orange intensity 8 had been the maximum. So this was definitely stronger shaking. And unfortunately it looks to be pretty high levels of shaking there in Ridgecrest.”
Ghilarducci said, “As you know over the last couple of days there have been a series of earthquakes that have occurred in the Ridgecrest area specifically around China Lake and Naval Station, and tonight around 8:20 p.m. there was a second very large quake, magnitude 7.1. The quake did last for some time, it was felt widely throughout most of Southern California and even as far north here as Sacramento. We have significant reports of fires, structure fires, mostly as a result of gas leaks, or gas line breaks. There are gas line breaks throughout the city. There are also reports of water main breaks, power is out, and communication is out to parts of the community. As well, south of Ridgecrest in San Bernardino County, the town of Trona, a small community of about 2,000, there are reports of also some building collapse and power outages, and some gas leaks there as well. Earlier tonight (California) Governor (Gavin) Newsom did talk to the White House and requested a presidential emergency declaration to support our operations here in the state and provide federal assets and what we call direct federal assistance in support of all of the mutual aid assets that we are currently providing to mostly Kern County and some to San Bernardino County.”
Includes reporting from the Associated Press