On Monday, April 14, 2025, millions of people across Southern California received an alert on their mobile phones seconds before a 5.2-magnitude earthquake hit San Diego County, thanks to the ShakeAlert system developed by the United States Geological Survey (USGS). ShakeAlert, which began operating in California in 2019, detects seismic waves as soon as an earthquake starts and sends out warnings to people before the stronger, more destructive shaking (S-waves) reaches them. This early warning system allows individuals to take protective actions such as “drop, cover, and hold on,” providing precious seconds to minimize injury. The system operates through a network of seismic stations, which use fast-moving P-waves to detect seismic activity and send alerts before the slower, more damaging S-waves arrive. However, the effectiveness of the alert depends on distance: the closer you are to the epicenter, the less notice you receive. People in downtown San Diego, for example, received alerts only one to two seconds before the shaking, while those in Los Angeles had up to 10 seconds of warning.
This early warning system has proven to be a game-changer, offering a small window of time to prepare for seismic activity, potentially saving lives and reducing injuries. Although these seconds may seem minimal, they can make all the difference in allowing people to take cover or secure themselves before the shaking begins. ShakeAlert is built on the concept that even a few seconds’ notice can significantly reduce the risk of injury, particularly in situations like workplaces or crowded public areas where people may be caught off guard. As the system continues to expand, it now serves over 50 million people in California, Oregon, and Washington, with potential expansion into Alaska as funding allows.
While ShakeAlert provides an invaluable heads-up in the event of an earthquake, it cannot prevent the damage caused by seismic activity. The true key to protecting property and lives lies in proactive seismic retrofitting. Buildings that have undergone seismic retrofits are better equipped to withstand the shaking and prevent catastrophic damage. In fact, retrofitting is often the most cost-effective way to ensure both the structural integrity of a building and the safety of its occupants. Given that Southern California experiences frequent seismic activity, it’s crucial for property owners to invest in strengthening their buildings to withstand future earthquakes.
Seismic retrofitting not only reduces the risk of significant structural damage but also minimizes the financial toll of repairs and potential insurance claims. Retrofitting has proven to be a sound investment, as it strengthens older buildings and ensures they meet modern safety standards. The process involves reinforcing key structural components, such as foundations and walls, to increase a building’s resistance to seismic forces. This measure is especially critical for older buildings built before modern earthquake safety codes were established.
Combining earthquake preparedness tools like ShakeAlert with seismic retrofitting can make a significant difference in reducing the financial and personal toll of an earthquake. As we continue to advance earthquake detection systems, building safety must also evolve to ensure that we are not only warned but also prepared. ShakeAlert can give you a few precious seconds, but it’s seismic retrofitting that will protect your property, your tenants, and your investment in the long run. For more information on how to retrofit your building for seismic safety, contact Optimum Seismic today.
Source: “How a Nifty Government Tool Knows About Earthquakes Before You Feel Them” – The New York Times, April 2025.
