Do Small Earthquakes Protect Los Angeles From the Big One? The Comforting Myth Gets the Science Backward

LOS ANGELES: After a cluster of small earthquakes, the same hopeful idea often returns. Perhaps the fault is letting off steam. Perhaps enough little shakes can release the pressure that would otherwise produce the Big One. The thought is comforting because it turns unsettling movement into a kind of protection. Earthquake science does not support it. Small quakes release energy, but not nearly enough to drain a major fault safely.

Magnitude is not a simple counting scale. It is logarithmic. Each whole-number increase represents about 32 times more energy release. That means one magnitude 7 earthquake releases roughly a thousand times the energy of a magnitude 5. Replacing one large event would require an enormous number of smaller ones, not the few tremors people notice during an active week.

Earthquake drills turn uncertain timing into actions people can practice before strong shaking begins. Image: U.S. Air Force photo by Sarah Corrice / Public domain

The arithmetic becomes even less reassuring at lower magnitudes. Millions of magnitude 3 earthquakes would be needed to equal the energy released by a magnitude 7. Those events would also have to occur on the relevant locked parts of the fault in a way that reduced stress rather than shifted it. Real faults do not behave like a pressure gauge that steadily empties with every small vibration.

Earthquakes happen when stress overcomes friction and rock slips along a fault. A small earthquake relieves stress on a limited patch, but it can slightly increase stress nearby. Most small events end without anything larger following. Some are aftershocks. Some are part of a swarm. A small fraction are foreshocks, a label scientists can apply only after a larger earthquake occurs.

That last point explains why experts cannot promise that a felt quake is harmless or a warning. The United States does not have a system that predicts the exact time, place and magnitude of a future earthquake. Scientists can estimate long-term probabilities, map faults and rapidly detect shaking after it begins. They cannot look at one minor event and know with certainty what the fault will do next.

Southern California has many faults, and not all of them are obvious at the surface. The San Andreas receives the most attention, but damaging earthquakes can occur on faults closer to dense neighborhoods. The 1994 Northridge earthquake struck on a previously unidentified blind thrust fault. Distance, depth, soil conditions and building strength can matter as much as the number printed beside an event.

The practical danger of the myth is false reassurance. If people assume small earthquakes have made the region safer, they may postpone securing furniture, storing water or checking insurance. The useful response is almost the opposite. A felt quake is a reminder that the region is active and that preparation works even when prediction does not.

During shaking, the standard advice is to drop, cover and hold on. Running outside exposes people to falling glass and exterior debris. In bed, staying there and protecting the head with a pillow is usually safer than crossing a dark room. Afterward, check for injuries and hazards, expect aftershocks and follow official information rather than screenshots stripped of context.

Preparation should fit ordinary life. Fasten tall bookcases, move heavy objects away from beds, keep shoes and a flashlight nearby and choose an out-of-area contact. Store water, medication and supplies for people and pets. These steps are less dramatic than trying to read a fault through social media, but they reduce the injuries and confusion that happen when strong shaking finally arrives.

Apartment residents can ask management how gas shutoffs, elevators and emergency communications will work. Businesses should know who checks utilities and who accounts for staff. Families can practice at different times of day because the safest cover at home may not exist at school or work. A plan becomes useful when everyone knows their first action without waiting for a group chat.

Small earthquakes are not useless. They help scientists map structures, study sequences and improve hazard models. What they cannot do is guarantee that Los Angeles has escaped a larger event. The right lesson is not that every tremor means disaster, or that enough tremors prevent one. It is that the timing remains uncertain while the hazard is real. Preparedness is valuable precisely because the earth does not send a schedule.