California Experiences Dozens of Earthquakes Per Day - But Why?

You may not usually feel it, but the ground in California is always moving. Why is this state so prone to earthquakes, how many does it experience per day, and how can you protect yourself? Here is all that you need to know about this mysterious force of Mother Nature.

Why Does California See So Many Earthquakes?

California sits on one of the busiest seismic zones in the world. The persistent shifts in the ground deep below the surface are responsible for the onslaught of earthquakes. While most of the quakes are barely detectable tremors, some of the stronger events are capable of causing significant destruction.

According to the Berkeley Seismology Lab, California records roughly 70 earthquakes each day on average. Most of these quakes are only detected by instruments. On an annual basis, the Golden State notches about 25,000 earthquakes. The bulk of these quakes come in between magnitudes 1.0 to 3.0, making them unnoticeable to people just going about their day.

California averages just two to three earthquakes per year that come in at magnitude 5.5 or greater. These quakes are large enough to trigger moderate damage. The degree of damage is dependent on the location relative to urban areas and the depth of the quake.

The reason why California sees so many earthquakes lies in its geography. The state sits at the boundary between two of the world's largest tectonic plates. The Pacific Plate and the North American Plate are always moving, squeezing past each other at varying speeds to cause the friction.

The plates occasionally bump into each other as they move and shift. The increased stress on the edges of these plates produces cracks known as "faults" over time. The zone where the faults bump into each other is known as the fault line. An excess of friction between the fault lines is what ultimately causes the seismic waves that trigger the earthquake.

California also has over 500 active faults, naturally making it extremely susceptible to earthquakes. Most people have heard of the San Andreas Fault, a line that runs about 800 miles, forming the main boundary between the two tectonic plates. Other major fault lines in California include the Hayward Fault in the San Francisco Bay Area, Southern California's San Jacinto and Elsinore faults, and the Calaveras Fault in the central part of the state.

It is interesting to note that not all earthquakes happen on land. Some of the most prolific quakes in history have happened offshore near the Mendocino Triple Junction. This is where the Pacific, North American, and Gorda tectonic plates converge, creating one of the most active areas along the West Coast.