5% Chance Today’s 6.4 Magnitude SoCal Earthquake May Only be a Foreshock, Officials Warn to be Prepared

Although today’s 6.4 earthquake was eipicentered near Death Valley and was not heavily felt in Pasadena, officials warn to be vigilant and be prepared. There is a 5% chance the event could have been a foreshock and a larger earthquake could follow, they said, noting aftershocks have already occurred.

Today’s temblor was about five and a half miles deep and was centered near Searles Valley or Ridgecrest, Dr. Jen Andrews, staff seismologist at the Caltech Seismology Laboratory told Pasadena Now.

“We saw one foreshock within about half an hour of the main shock magnitude 4. And we’ve seen obviously somewhere between 40 and 50 aftershocks so far, the largest being a magnitude 4.6. And we’re continuing to record those, we expect more in the next hours today.”

Andrews also noted that there is a small chance that this could have been a foreshock and an even larger earthquake could still occur.

“And there’s always a small chance in Southern California that this is again, a foreshock to an even larger main shock, but we don’t have any very long, continuous faults in this area. At the nearest that we have is a little lake fault.” Andrews continued, “but we’re still working on any kind of association with faults in the area.”

Pasadena Public Information Officer Lisa Derderian said, “There have been numerous aftershocks and they will continue so it’s important to be vigilant and prepared but also enjoy this Independence Day.”

Derderian was mindful that one of the biggest Fourth of July shows in Southern California goes on tonight in the Arroyo.

“The show will go on tonight at the Rose Bowl. Out of an abundance of caution our Fire Department and Building and Safety staff conducted a safety assessment of the Stadium and there are no issues,” Derderian said. “No damage has been reported in the City of Pasadena. Please come see the biggest professional fireworks show in Southern California at the Rose Bowl tonight. Gates open at 5:30 pm.”

Derderian also said the shaker is a reminder for residents to practice disaster plans at home and work and know the plans in place at your child’s school.

Even though there was no damage, Andrews cautioned that with an earthquake of this size, there is always a chance that it could trigger other faults nearby if they were ready to fail. She said Caltech will be monitoring the situation.

Andrews pointed out that, “There’s always a chance. So we’re working that out based on sort of the statistics of what we see in the past catalog and how the Earth behaves. So it is a small chance, about one in 20 or 5%, we say that this could be a precursor to something larger, but it’s just good to be aware.”

Her advice is to, “be prepared for aftershocks in the next hours or days, that’s definitely to be expected. And then just all the general preparedness advice. So if we say it could trigger something else to go if, if another fault nearby is ready. So be prepared, have your water, have your food, have your communications plan with your family. Other than that, enjoy the 4th of July.”

Derderian continued, “Fortunately today is a holiday where families are home and less people are on the roads at school or at work. Our fire stations have checked their respective districts are no damage has been reported.”