California’s Uptick in Earthquake Activity Explained: Should We Be Concerned?

California residents were left trembling earlier this week when more than 400 tremors were felt across the state following a 5.2-magnitude earthquake that struck the Bakersfield area. 

Residents felt the earthquake just after 9pm on Tuesday, August 6th, in the Central Valley area roughly 90 miles north of central Los Angeles. The earthquake was felt throughout Los Angeles, Ventura, and Kern. In the days that followed the initial quake, a further 74 smaller earthquakes ranging in magnitude, but all sitting close to the 2.5 mark, were felt within a ten-mile radius of the epicenter. 

Social media users expressed their shock at the seriousness of the earthquake, and one scientist even shared video footage of a seismograph at the Griffith Observatory monitoring the earthquake in real time. X user @JaredHead, a rocket scientist at the Los Angeles Griffith Observatory, shared the clip on August 7 and followed up with an additional post detailing the seismograph results.

“We were able to get the 5.2 Bakersfield #earthquake on video in real-time on the seismographs at @GriffithObserv. But this is what the paper on the rightmost drum looked like after we removed it. Maxed out, with plenty of aftershocks. Currently showing it off to the public!” the user wrote.

While the U.S. Geological Survey revealed an enormous number of earthquakes over the last week alone, those numbers started to decline as of Thursday. It follows a pattern typical for earthquakes, not just in California but all over the world, where one large earthquake is typically followed by a series of additional and less severe quakes known as “aftershocks.”

How Aftershocks Work

Aftershocks still count as earthquakes but are typically much less serious than the initial quake that triggered them, which is known as the “mainshock.” Aftershocks occur in the same region as the initial mainshock and are caused by the Earth’s crust adapting to the changes that occurred during the initial earthquake. Earthquakes are the result of tectonic plates moving over soft magma in the earth’s crust – and as those plates move and shift, aftershocks continue until the plate finds a new resting position. The pattern of aftershocks is not always predictable as it is impossible for us to know the exact position of tectonic plates at any one time, but we do know that they gradually disappear over a short period of time. 

This gradual process of shocks becoming less intense over time and occurring in smaller numbers is known as Omori’s Law. The origins of the law have been the subject of extensive debate among scientists for decades. A newer theory, the Omega Theory, also suggests that Omori’s Law may not be a fundamental law of nature but instead the result of “Omega-sequences,” which refers to a sequence of earthquakes. These sequences are patterns of seismic activity that appeal to follow some kind of geometric progression. The Omega Theory, therefore, suggests that the pattern of aftershocks following an earthquake are largely mathematically predictable based on how the crust adjusts following the main shock. 

A Noticeable Uptick in Earthquake Activity 

California already has the most earthquake activity in the country, accounting for more than two-thirds of all quakes that occur every year. The risk of earthquakes in the region, therefore, is high at any point in time. According to data from the Uniform California Earthquake Rupture Forecast, there is a more than 99% risk of a major earthquake that registers more than 6.7 on the Richter Scale within the next 30 years, starting in 2014. There is also a 75% chance of a 7.0 quake occurring in Southern California in the same period, and a 76% chance of a 7.0 quake occurring in Northern California. 

Quakes occur as a result of the many thousands of known fault lines resting underneath the state. New faults are being discovered all the time, meaning residents of the state should always be prepared. 

California has seen an uptick in the number of earthquakes in recent times. Over the past month alone, between July and August, there have been nearly 1,000 earthquakes recorded in the state. While most were minor, some have reached magnitudes of more than 4.0. 

More broadly, California experiences roughly 46,000 earthquakes per year, with an average of 503 earthquakes registering at magnitudes of 3.0 or higher. 

How California Prepares

While Californians already know the basics of preparing for an earthquake. An advanced early warning system now provides residents with as much warning as possible before a quake hits. That being said, that “advance” warning only gives residents a 35-second heads-up. 

The first-in-the-nation Earthquake Early Warning System connects with state residents via the MyShake app. On Tuesday, when the latest major earthquake occurred, more than 517,354 alerts were sent across the state. Following the most recent earthquake, a further 46,692 people downloaded the app in a space of 12 hours. The new technology does more than just warn people that an earthquake is coming; the tech is being integrated into fire stations and private business properties across the state. Properties across the state that have partnered with the state government will soon see firehouse doors open automatically as quakes begin, elevators recalled, and water and gas valves shut off automatically. 

While the new tech is impressive, the fact remains that scientists still do not have any reliable way to predict when an earthquake is coming beyond mere seconds. Based on existing technology, all scientists can do is analyze trends and document an uptick in the number of quakes occurring over a specific period of time – but these trends do not predict the future and do not necessarily indicate that more earthquakes are coming.