Living with Earthquakes in California: Myths, Facts and Safety
California is one of the most seismically active regions in the world, experiencing frequent tremors ranging from minor shakes to potentially catastrophic events. While most earthquakes in California go unnoticed, larger ones can cause widespread damage, endangering lives and property.
This article explores the frequency, causes, and impacts of California earthquakes while debunking myths and providing key facts to help you stay informed and ready.
Earthquake Activity in California: What You Need to Know
Earthquakes are a frequent yet often misunderstood natural phenomenon.
Most earthquakes in California are small in magnitude and often go unnoticed. For example, the Napa Valley region, north of the Green Valley Fault, experiences thousands of small temblors each year due to its proximity to active fault lines.
What Causes Earthquakes?
Earthquakes happen when the Earth’s crust suddenly shifts along fault lines. This movement occurs because tectonic plates constantly push against each other, building up pressure over time.
Tectonic plates on Earth. Source
When the pressure becomes too great, the ground moves, releasing energy and causing the shaking we feel during an earthquake.
Can Earthquakes Be Predicted?
No. While scientists can estimate the likelihood of a major earthquake within a specific timeframe, they cannot predict the exact time or place.
How Many Earthquakes Happen in California Daily?
California experiences dozens of earthquakes each day, but the vast majority are so small that they go unnoticed. These tiny tremors are typically below magnitude 3.0 and are detected only by sensitive seismic instruments.
While these minor quakes pose little to no danger, they are a constant reminder of California’s active fault lines and the potential for larger, more damaging earthquakes.
Understanding this frequent activity highlights the importance of preparedness for when a significant earthquake does occur.
What Is “The Big One”?
“The Big One” refers to a hypothetical massive earthquake expected to occur along California’s San Andreas Fault or another major fault line in the region.
This term is often used to describe a potentially catastrophic event that could severely impact densely populated areas, damaging infrastructure, disrupting services, and endangering lives.
Experts agree that a significant earthquake could strike California or the West Coast anytime. While the exact timing of “The Big One” is unpredictable, the potential impact underscores the critical importance of preparedness.
The U.S. Geological Survey (USGS) estimates:
- There is a 72% chance of an earthquake measuring magnitude 6.7 in the San Francisco Bay Area within 30 years.
- There is a 60% chance of an earthquake measuring magnitude 6.7 in the Los Angeles Area within 30 years.
Is the West Coast Prepared for the Next Big Earthquake?
Recent events, such as the December 2022 magnitude 6.4 earthquake near Ferndale, California, highlight the region’s vulnerability. This quake left 70,000 residents without power, damaged critical infrastructure, and caused injuries and fatalities.
While California experiences frequent, smaller quakes, Washington and Oregon typically see fewer earthquakes. However, they are often stronger due to the Cascadia Subduction Zone.
Organizations like the Structural Engineers Association of California (SEAOC) emphasize the importance of proactive preparation. They provide resources for earthquake readiness, focusing on the risks of aftershocks and the potential for increased seismic activity following a major quake.
Given the unpredictable nature of earthquakes and their widespread impact, preparedness is not optional—it’s essential. Taking steps now can help mitigate damage and save lives when “The Big One” strikes.
What Is an Aftershock?
Aftershocks are smaller earthquakes that occur after a significant seismic event as the Earth’s crust adjusts to the initial rupture.
Aftershocks tend to decrease in frequency and intensity over time. Still, they can continue for weeks, months, or even years, often worsening damage to buildings and structures already compromised by the main quake.
How Many Aftershocks Are Normal After an Earthquake?
The number of aftershocks following an earthquake can vary widely depending on the magnitude of the main quake and the geological conditions in the area.
Typically, larger earthquakes produce more aftershocks. For instance, after a magnitude 6.4 earthquake near Ridgecrest, California, in 2019, over 100,000 aftershocks were recorded the following year.
These aftershocks tend to decrease in frequency and intensity over time but can continue for weeks, months, or even years.
“Hurriquakes” and Other Unusual Disasters
In August 2023, California experienced a rare “hurriquake,” where a tropical storm and a 5.1-magnitude earthquake occurred simultaneously. While unusual, this event highlights the growing intensity of natural disasters fueled by natural climate and geological changes.
The combination of these two hazards reminds us that multiple disasters can overlap, making preparedness plans essential for individuals, businesses, and communities.
Earthquake Myths
Earthquakes are surrounded by many misconceptions that can lead to a false sense of security or unnecessary fear. In this section, we’ll debunk some of the most common myths to provide a clearer understanding of seismic risks and preparedness.
Myth: Earthquakes only happen on the West Coast of the U.S.
Fact: Earthquakes can occur anywhere. According to the USGS, nearly 75 percent of U.S. states could experience a damaging earthquake.
Notable examples include the widely felt 2011 earthquake in Virginia, which affected areas not commonly associated with seismic activity.
National Seismic Hazard Model (2023). Map displays the likelihood of damaging earthquake shaking in the United States over the next 100 years.