A moderate earthquake with a magnitude of 4.4 struck the Los Angeles area on Monday afternoon, with its epicenter located in the El Sereno neighborhood. The tremor was widely felt across Southern California, from the heart of Los Angeles to regions as distant as San Diego and Ventura. Despite the extensive reach of the quake, there were no immediate reports of significant damage.
The earthquake occurred at approximately 12:20 p.m., with its epicenter pinpointed around 1,000 feet southwest of Huntington Drive and Collis Avenue in El Sereno. Although the shaking was intense enough to knock bottles off shelves at a Target store in Alhambra, and cause a burst water pipe at Pasadena’s City Hall, no major structural damage has been reported. According to the L.A. County Fire Department, emergency services did not receive any damage reports, and the South Pasadena Police Department only responded to multiple home alarms triggered by the quake.
@LegsESPN (Timothy Legler) “Nothing like being on the set for live TV when an earthquake hits! Wild day in the LA studio with @malika_andrews for NBA Today. Hopefully everyone is safe. I’m sure Californians are used to this but very different for an East Coast guy like myself”
Twitter August 12, 2024 https://x.com/LegsESPN/status/1823093996199321913
Analysis of the Fault System
Seismologist Lucy Jones, a research associate at Caltech, noted that the earthquake took place within the same fault network responsible for the 1987 Whittier Narrows earthquake, which had a magnitude of 5.9. However, it remains uncertain whether the quake occurred on the Puente Hills thrust fault, the Lower Elysian Park thrust fault, or possibly a secondary system between these two faults. Both the Puente Hills and Lower Elysian Park thrust faults are buried deep underground, complicating efforts to determine the exact fault responsible for the event.
“When we’ve tried to image them — which is not easy, right? — … we see a web. We don’t see one clear system. And we see several different strands,” Jones explained. “We need to remember this is only a four-and-a-half, and therefore, associating it with a particular fault is always going to be problematic.” She also confirmed that the earthquake did not occur on the Raymond fault, which is a fault that can be clearly mapped.
Early Warning System Success
Many residents in Southern California received advance alerts on their smartphones, warning them of the impending quake. This was another success for the region’s earthquake early warning system, which has been steadily improving in accuracy and reliability. Individuals with iPhones or those using the MyShake app, developed by UC Berkeley in collaboration with the California Governor’s Office of Emergency Services, were among those who received the early warnings. The app provides alerts to users in California, Oregon, and Washington. San Diego County residents can also access similar alerts through the free SD Emergency app, which includes the ShakeReadySD earthquake early-warning tool.
For those without smartphones or early-warning apps, earthquake alerts are still possible through the Wireless Emergency Alert system, a service that sends alerts to cellphones based on the projected magnitude and shaking intensity at the user’s location, similar to the system used for Amber Alerts.
The Importance of Preparedness
The magnitude 4.4 earthquake that shook Los Angeles serves as a reminder of the ever-present seismic activity in Southern California. While this event did not cause major damage, it underscores the importance of earthquake preparedness and the value of early warning systems in mitigating the impact of future quakes. As these systems continue to evolve, they offer crucial seconds of advance notice that can save lives and reduce harm during more powerful seismic events.
