Americans have always feared a big earthquake and the associated earthquake risk. We call it “The Big One.” It could shake the West Coast badly. On Friday, a 7.7 magnitude earthquake hit Thailand and Myanmar. It caused terrible damage. Many people are feared dead. Buildings are destroyed. There are worries about flooding and dam collapses.
But now, earthquakes are happening all over America. People in many parts of the country worry they could be sitting on a “time bomb.” Geologist Robert Yeats wrote a book called “Earthquake Time Bombs.” He warns that big cities in the Pacific Northwest could be in danger due to earthquake risk.
The Cascadia Subduction Zone
The Cascadia Subduction Zone is a big risk. It stretches from Northern California to Canada. It sits under Oregon and Washington, too. This zone is where two tectonic plates meet. One slides under the other. This can cause the biggest earthquakes. When the plates rub against each other, pressure builds. When the pressure becomes too much, the plates suddenly move. That’s when we feel the earthquake, highlighting the persistent earthquake risk.
Experts say that there have been eight big quakes in the last 3,500 years. They think another one could happen soon. The last big quake in this zone was in 1700. It was so strong that it caused huge tsunami waves. The earthquake shook the area for miles, showing the ongoing earthquake risk in the region.
If a big earthquake happens today, it could be the worst disaster in America’s history. Thousands of landslides could happen. Bridges would fall. FEMA says 85% of ports and water plants would be damaged. Almost 80% of airports, schools, and hospitals would be destroyed.
How Long Between Big Quakes?
Scientists say the time between major quakes can be different in different areas. In the north part of the Cascadia zone, it could be 1,200 years. In the south, near California, it could be only 250 years. This makes many experts believe the next big quake is overdue and poses a significant earthquake risk.
If “The Big One” hits soon, it could cause gas lines to catch fire. A tsunami could also follow, like the one in Japan in 2011. In Oregon, $32 billion in property could be lost. Some towns along the coast would be submerged. The land could drop by as much as 10 feet, increasing the overall earthquake risk.
San Francisco and Northern California
In Northern California, there’s a nearly 75% chance of an earthquake soon. In San Francisco, it’s even higher. This region has had many big earthquakes. One of the worst was in 1906. That quake killed over 3,000 people and destroyed most of the city. Thousands of buildings burned down. Rebuilding the city cost billions of dollars, further emphasizing the earthquake risk.
Experts say the three biggest faults in Northern California are the Hayward Fault, Calaveras Fault, and San Andreas Fault. These faults are dangerous because they run along the coast. They could cause a big quake anytime, adding to the area’s earthquake risk.
Southern California
Southern California is also at high risk. There are earthquakes almost every day. Between 2008 and 2017, 1.81 million quakes happened there. Most were too small to feel, but some were big. In 2024, Los Angeles had 2,420 quakes. Some were up to 4.6 in size.
The biggest quake in LA’s history was in 1994. The Northridge earthquake killed 60 people. It caused damage that cost billions of dollars. Los Angeles is near the San Andreas Fault, which causes many big earthquakes. If a big quake strikes, it could kill up to 1,800 people and cause $213 billion in damage, highlighting the significant earthquake risk.
