It started with a shock a 3.8 quake on Nov. 9 and has continued ever since, with more than 300 earthquakes shaking beneath the very feet of San Ramon residents in the past month alone. The “Big One”? It could be coming soon, at least if a heightened sense of earthquake preparedness in the Bay Area’s East Bay community of San Ramon has anything to do with it.
1. Swarm That Won’t Quit
The swarm has been unrelenting. Earthquakes have been so weak they’ve barely registered. Others, like the latest one at a magnitude of 4.0, have been strong enough to knock items off the shelves. The U.S. Geological Survey has confirmed at least 80 earthquakes of magnitude 2 or later have hit the San Ramon area since last November. The swarm is concentrated on the Northern part of the Calaveras Fault. This section of the fault line has had nine prior swarms since the year 1970. None of those swarms precipitated a catastrophic event.
2. Why Swarms Don’t Always Signal Disaster
“There’s gonna be a big earthquake in the Bay Area. We just can’t say exactly when and where. So you should be ready for that,” said USGS seismologist Annemarie Baltay. “Some big earthquakes have been preceded by smaller earthquakes. But many earthquakes have not. The chance of having an earthquake followed by an even stronger one is 5 percent for the next three days” if there is a moderate one. “Half of large earthquakes are not preceded by any detectable earthquakes,” Annemarie continued.
3. California’s Unavoidable Risk
What it means to be a Californian is to live in earthquake country. According to the Geological Survey of California, there are 15,000 known faults in the state, of which more than 500 are known to be active. According to the estimates of the USGS, the probability of having an earthquake of magnitude 6.7 or more in the San Francisco Bay area is 72 percent in the next 30 years, whereas the probability for the state of California is more than 99 percent.
4. The Calaveras Fault and Its Neighbors
The Calaveras Fault, while not aswell-known as the San Andreas Fault, has been identified as one of the most probable causes of significant seismic events in the Bay Area. The Calaveras Fault broke in 1984 and caused the Morgan Hill earthquake with a magnitude of 6.2, resulting in injuries to 21 people and $7.5 million damage. Another significant fault line in the region is the Hayward Fault. The Hayward Fault has the capability of displaceing upwards of tens of thousands of households.
5. Lessons from Past Seismic Clusters
Swarms that fizzled out are known in history. Malibu, Ontario, and El Sereno experienced a cluster of earthquakes before fizzling out. History lessons on a swarm can be a reality check: “The Ridgecrest sequence of earthquakes began with a 6.4 quake on July 4, followed by a 7.1 on July 5.” In 1857, two moderate earthquakes happened before a massive 7.8 Fort Tejon earthquake on the San Andreas fault.
6. Building Mental Resilience Amid Uncertainty
Frequent earthquake tremors can be frightening and lead to a fear state of constant anxiety. Professionals advise managing by focusing on earthquake preparedness, which can help to restore some control of one’s life. Recognizing that earthquake swarm activity does not mean disaster is imminent can alleviate fears, but recognizing risk encourages earthquake safety preparedness.
7. Action Steps for Protecting Home and Family
Home earthquake safety begins with home earthquake preparedness. Seismic retrofits of homes, especially homes built before the year 1980, can prevent homes from sliding off their foundations during an earthquake. There are grant programs for seismic retrofits from the California Earthquake Authority, which can be used as a means of paying for retrofits. Other precautionary measures, such as securing a water heater, securing heavy furniture, and maintaining emergency kits, make a big impact. There are seven home earthquake safety tips from the Red Cross, including secure your space, plan for safety, organize supplies, reduce economic hardship, drop, cover, hold, improve safety, and reconnect.
8. Staying Informed Without Panic
There is a USGS calculator service which allows individuals to determine probabilities of earthquakes occurring in specific areas, as well as hazard maps which detail expected intensities of shaking. Through these services, individuals are able to assess their vulnerability without resorting to fear. Scientists have argued that although the Big One is inevitable and will eventually occur, it is impossible to predict exactly when it will happen, which is why preparation is the most pragmatic approach.
For people in San Ramon, the swarm is a prediction that has already been fulfilled. The earth may continue to quake for several days or even weeks, but past events indicate that many swarms will go out with a whimper rather than a bang in this state that has made earthquake hazards an integral part of life.
