Southern California has recently been shaken by several small earthquakes. They produced minor tremors and left that lingering question: is this the beginning of something bigger?
First, a magnitude 3.6 earthquake in the Ojai Valley sent weak tremors from Santa Barbara to Los Angeles on May 31. Then, two small earthquakes occurred in the El Sereno neighborhood of East Los Angeles, the most powerful being 3.4. Finally, a trio of quakes hit the Costa Mesa-Newport Beach border region, reaching a magnitude of 3.6 last Thursday.
Having half a dozen earthquakes with a magnitude above 2.5 in a week, hitting three distinct parts of Southern California, all in highly populated areas, is not a common occurrence.
But experts say these small quakes do not serve as a prediction for the next big and destructive earthquake in Southern California, the last of which occurred 30 years ago.
Overall, there is a one in 20 chance that any earthquake in California will be followed by a larger one, Susan Hough, a seismologist with the U.S. Geological Survey, told the Los Angeles Times. Those odds are not high, and typically, the subsequent larger earthquake should occur in the same area within a week. Furthermore, if something bigger does happen, the greater chance is that a new quake will only be slightly larger, Hough said.
Still, the recent earthquakes are a reminder that Southern California is deeply vulnerable to earthquakes. The risk is by no means limited to the region’s most famous fault, the southern San Andreas fault, which, besides running under San Bernardino and Palmdale, is mostly beneath deserts and remote mountains but is capable of triggering an 8.0 magnitude earthquake.
In contrast, last week’s earthquakes highlighted nearby fault systems directly beneath populated cities, which could produce an even higher number of fatalities than the San Andreas mega earthquake.
Although some cities and government agencies have taken significant steps to protect infrastructure, such as retrofitting older buildings, many others have yet to take actions that mitigate seismic vulnerabilities.
Puente Hills Fault
The Puente Hills fault is particularly concerning because of what is above it – downtown Los Angeles, which has many old and unretrofitted buildings, as well as large areas of southeast L.A. County, the San Gabriel Valley, and northern Orange County.
But there is a glimmer of hope: unlike the San Andreas fault, which generates a major earthquake on average every 100 years or more, the Puente Hills fault produces large earthquakes only every two thousand years.
Source: Los Angeles Times