California Tremors: Why Earthquakes Shake the West Coast. Part 1 of Our Tremors Series.

A fault line crack in Highway 178 is opened by a powerful magnitude 7.1 earthquake, triggered by a 6.4 the previous day, near the epicenter in Trona, California, U.S., July 6, 2019. Picture taken July 6, 2019. REUTERS/David McNew
A fault line crack in Highway 178 is opened by a powerful magnitude 7.1 earthquake, triggered by a 6.4 the previous day, near the epicenter in Trona, California, U.S., July 6, 2019. Picture taken July 6, 2019. REUTERS/David McNew

Editor’s note: This is part one of watchourcity.com’s ongoing series on California earthquake history, preparedness, and response.

California is known for a lot of things: sunshine, movies, beaches, surfing, and horrible traffic. But perhaps one of the most famous things that are synonymous with California is perhaps almost one of the most detrimental – Earthquakes.

When settlers first came to California and put down buildings, irrigation for farming, and rudimentary roadways; they, unfortunately, didn’t know the state was one of the more prone on the North American continent for geological activity.

The State of California is geographically in a precarious position. To the north of the state lies the Mendocino Fracture Zone, a submarine fracture zone, which overlaps with the Cascadia Subduction Zone, a “megathrust” fault, to the South the San Andreas Fault, a transform fault that is located directly on the shifting edge of the Pacific tectonic plate and the North American tectonic plate.

seismic activity earthquake map

When the intersection of these three zones, called a triple junction, as well as the tectonic shifting in the south of continental plates, falls right in the midst of the Los Angeles basin where Los Angeles city, the second-most populous city in the United States is located, you have a bit of a problem.

Namely that at any time if the tectonic shifting is too much it could yield a very large and very devastating earthquake. While this can be scary, it also is a lot of information that gives us the ability to try and plan for the next major earthquake, which is often a very convoluted task.

Estimating how fault energy is release can be quite tricky. Due to the complex nature of faults and their irregular geometry, mapping and modeling how they will react become a difficult task.

Further, the higher the magnitude of an earthquake does not always mean it will be more d devastating. Take for instance the 1994 Northridge, CA magnitude 6.7 earthquake. It’s shaking caused massive property damage and death due to it striking in such a crowded area of Los Angeles.  

Yet the 2018 Fiji magnitude 8.2 earthquake, which was significantly more powerful of a quake, didn’t really do much in terms of property damage of human life as it was deep in the ocean and the surrounding areas it affected were not populated.

Just back in July, a 7.1 magnitude earthquake hit Ridgecrest California causing massive damage to the area. Fortunately, since Ridgecrest is not as populated as Northridge, the loss of life was minimal. There were two earthquakes that hit Ridgecrest both under 3.5 magnitude, but still a warning to a possible larger earthquake that may be in the future.

In the past few weeks, California has lived up to its name as a hotbed of earthquake activity as several earthquakes have rattled Southern California in particular.

Yesterday, November 13th, a 3.9 magnitude earthquake hit near the areas of Ridgecrest and Trona California, stoking fears that another large earthquake like the one in July, would soon be upon residents of Ridgecrest.

This, of course, was right after yesterday, November 12th, when a 4.0 magnitude earthquake the California-Mexican border.

Tuesday’s quake was preceded by parts of the Coachella Valley which were hit with a magnitude of 3.5 about 10 miles north of Indio, California on November 11th.

That shaking was right on the heels of another 3.5 magnitude earthquake that hit on Sunday, November 10th, 13 miles away from Palm Springs, which followed three earthquakes over 3.0 magnitude that shook Ventura in under an hour and a half on the 8th of November, following two over 3.0 magnitude earthquakes on November 7th.

With all this consistent quaking where does that leave us? At present we haven’t any major earthquake hit Los Angeles County itself in over 25 years. However, with all the tremors around us and especially with quakes like the Ridgecrest earthquake back in July of 2019 and today, it is entirely possible that we will see another large earthquake close to or in the area, some experts say.

In fact, new research shows that the Ridgecrest earthquakes that began in July ruptured at least two dozen faults, which could be one of the reasons why there has been so many earthquakes in that area. It’s the latest evidence of how small faults can join together to produce a large earthquake, and how those quakes can cover a wider area than expected.

Just the fact that California has not experienced a major earthquake in some 25 years is statistically unlikely; in other words, the state is due for a serious shakeup.

But since USGS scientists can only calculate the probability that a significant earthquake will occur in a specific area within a certain number of years, not a certainty of an occurrence, your best bet is to be ready if an earthquake hits.

On Part 2 of our series on Earthquakes, we will cover how to be prepared for if a large earthquake hits so you can be ready and have an action plan if another large quake occurs.

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