California is overdue for a massive earthquake

The “Big One” could cause catastrophic damage, especially in Los Angeles
Residents are urged to prepare with earthquake survival kits

Recent increased earthquake activity in California has rekindled fears of the long-anticipated “Big One.” This major quake, expected to hit along the 800-mile-long San Andreas fault, could cause catastrophic destruction, with estimated death tolls reaching 1,800, injuries exceeding 50,000, and damages surpassing $200 billion, according to the California Earthquake Authority.

Although predicting the exact timing of such an earthquake is impossible, geologists believe the state is overdue for a major quake. Geologic evidence shows that a significant tremor along the fault typically occurs every 150 years, and it has been 167 years since the last one.

So far this year, California has experienced 14 earthquakes of magnitude 4 or higher—well above the average of eight for the region. While this spike in activity is not necessarily a warning sign, it has brought the possibility of the “Big One” back into focus.

Minute-by-minute breakdown of what could happen when california's 'big one' earthquake strikes

The San Andreas fault separates the North American and Pacific tectonic plates. When these plates get stuck due to friction, stress accumulates. Once this stress is released, it sends shockwaves that cause an earthquake.

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Both the northern and southern portions of the San Andreas fault are equally likely to trigger a high-magnitude earthquake. However, a rupture in the southern section, near Los Angeles, poses a particularly grave threat due to the densely populated areas along its path.

The Timeline: What Happens When the Big One Hits?

First 10 seconds: The dreaded cellphone alert

A magnitude 8 earthquake near the Salton Sea would trigger an earthquake alert within seconds.

Alerts would be sent via phones to people in the rupture’s path.
Initially, the shaking would be weak, with stronger tremors to follow.
The first waves, called P waves, travel fast but cause less movement compared to the more destructive S waves.

30 seconds: Buildings begin to collapse

Around 30 seconds in, cities like Palm Springs, within 60 miles of the epicenter, could experience intense shaking (intensity level 9).
S waves, which move slower but cause significant side-to-side movement, would topple buildings and knock people off their feet.

Areas further from the fault, like Blythe, would see strong to very strong shaking, risking building damage.

One minute: LA endures the brunt

Los Angeles would experience minor tremors 45 seconds in, followed by intense shaking (intensity level 9) at around 90 seconds.

Due to the soft sediment in the LA basin, seismic waves could become amplified, causing extensive damage.
Buildings would crumble, and infrastructure damage would be widespread, with likely injuries and fatalities.

Two minutes and beyond: Aftershocks

Aftershocks, following the main tremor, would set in quickly, possibly causing further damage.
Magnitude 6.5 aftershocks could occur, though their timing and severity are unpredictable.
Aftershocks can continue for days, weeks, or even years, although they typically decrease in intensity over time.

Preparedness Is Key

California has strong building codes, and emergency plans are in place, but many residents are not fully prepared.
Earthquake kits, two-week water supplies, and emergency food and medication stores are crucial for survival in the event of a disaster.