What if California was hit by a strong 8.2 earthquake?
Meteorologist, PhD
Tuesday, November 14, 2017, 1:35 PM - On Nov. 7, 2017, a 3.2 earthquake shook Los Angeles in the middle of the night, waking-up residents and lighting up thousands of alarms on local social media networks. According to the USGS the epicenter was 7.5 miles deep and centered in the West Athens area, not far from Los Angeles International Airport.
Just two months earlier, on Sept. 7, the ground moved violently in Chiapas when a powerful 8.2 quake, the strongest in a century for Mexico, caused serious structure damage to 41,000 homes and close to 100 hundred casualties. Then on Sept. 19, 2017, a 7.1 quake struck near the Mexican states of Puebla and Morelos, bringing down close to 40 buildings in the Mexico City metro areas and killing 370 people and injuring more than 6,000.
All this recent activity has brought up the same question locals ask year after year when the ground shakes: What if California was hit by an 8.2 quake like Mexico?
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Watch below:Emergency services helped to rescue a man who had become trapped in a collapsed textile factory in Mexico City, after a 7.1 magnitude earthquake hit the area, killing more than 200.
Scientists have no problem affirming it is possible for California to experience an 8.2 magnitude quake. The San Andreas fault stretches 800 miles along California ground making it the longest in the state and one of the most dangerous in the world.
The last time it triggered a considerable earthquake in southern California was in 1857, when a magnitude 7.9 jolted the ground along the San Gabriel Mountains near Los Angeles. In 1906 it caused one of the most remembered quakes on record in San Francisco, a 7.8 which destroyed most of the city and claimed the life of 3,000 people.
San Francisco Earthquake Aftermath, 1906; Creative Commons
The San Andreas fault is "locked, loaded and ready to roll"
According to Southern California Earthquake Center director Thomas Jordan, the most famous fault in the world has been quiet for a long time, too quiet, and is now "locked, loaded, and ready to roll".
San Andreas fault line
Scientists warn that if we just follow some general rules of plate tectonic movement, with the Pacific Plate moving northwest of the North American Plate, earthquakes in the region should be retreating by about 16 feet of accumulated plate movement every 100 years. However, the San Andreas fault has yet to relieve the stress accumulated over more than a century.
Los Angeles would suffer the greatest impact
Although several other areas of the fault are long overdue for a large earthquake, scientists are especially concerned about the southern sector.
According to the U.S. Geological Survey, every 150 years this section of the fault can produce a sizeable earthquake. If an 8.2 quake where to occur tomorrow, the second most populated city in the U.S., Los Angeles, would suffer a big blow.
The shacking would rupture the San Andreas fault from the Salton Sea near the Mexico border, all the way northwest to Monterrey. Some heavily populated counties like Los Angeles, San Bernardino or Riverside would be affected.
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The impact for Southern California would be much greater than in Mexico, because the San Andreas fault runs through densely populated areas and is only 30 miles from downtown Los Angeles (see shaking intensity map below). A magnitude 8.2 earthquake along the San Andreas fault would produce level 10 shaking -- which is extreme-- and could raise the death toll to 1,800. This figure comes from a study from the USGS for a 8.2 magnitude quake occurring along the San Andreas Fault near Los Angeles at 10 a.m. on a calm dry November Thursday. Of these potential deaths, 900 would be fire related, 400 from steel-frame building collapse, more than 250 from other building collapses, and 150 from transportation related accidents.
Intense shaking GIF animation: This animation shows how intense shaking is directed from the San Andreas Fault to the Los Angeles Basin. Yellow = strong, Orange = very strong, Red = violent or extreme. (US Geological Survey & Southern California Earthquake Center)
Potential impact on L.A.
It's impossible to predict an exact time frame to the next large earthquake in Southern California, but scientists agree a considerable earthquake will hit Southern California within the next 30 years. For many Californians, it has been the same old song for decades.
6.7 earthquake in Northridge, California in 1994 (Courtesy: Shuttershock/Creative Commons)
The San Andreas fault has caused some relatively recent earthquakes, like the 1989 6.9 registered in the Loma Prieta area of northern California.
The largest, most recent earthquake in Southern California occurred in 1994, when a 6.7 shook Northridge. However, it did not occur along the San Andreas, rather another nearby fault system.
In the past, major earthquakes in California occurred when population density was much lower. Today, close to 38 million people would be affected by a major earthquake along the San Andreas fault.
Watch below: Science Behind Earthquakes
How intense could it be?
In the 2015 film "San Andreas" a 9.0 magnitude earthquake causes massive destruction across the state of California. One has to wonder, how much of this will even be close to reality?
Earthquakes this strong have occurred in the past, and how much damage they caused had a lot to do with the nature of their respective tectonic regions. In Chile and Japan, for example, the tectonics are different than in California, where two tectonic plates are sliding next to one another, rather than above and below each other.
Watch below: San Andreas movie trailer
Recent predictions limit the intensity of a San Andreas quake in Southern California to an 8.0, and there is a seven per cent probability that it could occur in the next 30 years. However, over the same period, the probability of a 7.0 or greater occurring does rise to 75 per cent.
The difference between a 7.0 and an 8.0 may not sound like much, but it is considerable, given that earthquake intensity and the resulting energy release grows exponentially.
USGS Fault Map
Whether it is a 7.0 or an 8.0, damage is inevitable. The good news is that the San Andreas fault runs under land and not under the ocean, so a major tsunami would not be an issue in major urban areas like Los Angeles or San Diego from the movement of this major fault alone.
