home Top News Earthquake talk with the California Geological Survey

Earthquake talk with the California Geological Survey

Brandon Yu | brandonyu19@dtechhs.org | June 7, 2018

Earthquakes like the recent 4.5 magnitude earthquake that happened on May 8 in Southern California serve as grim reminders to us all that although we Californians may not have to worry about tornadoes or blizzards, we are faced with the constant risk of earthquakes. So how worried should we be? The California Geological Survey maps and analyzes data on our state’s geological environment to provide necessary information with the goal of protecting California’s residents and environment. The Dragon spoke with Don Drysdale, a member of the Public Affairs Office, to learn more about the safeguards put in place to detect earthquakes and what people can do to prepare for them. The following interview was excerpted and edited for clarity.

Q: Why does California get so many earthquakes when compared to the rest of the United States?

The surface of the world sits on gigantic tectonic plates that typically move very gradually. California sits on the border between the North American and Pacific tectonic plates. Los Angeles is on the Pacific plate, which is moving very slowly to the northwest. San Francisco is on the North American plate, which is moving very slowly to the southeast. Sometimes these giant plates get a bit stuck as they slide past each other and then move suddenly with a jerk; that’s an earthquake. In other parts of the world, one plate pushes another plate down. In areas where this happens – subduction zones – you get really enormous earthquakes, like the magnitude 9.1 event in Japan in 2011. There’s a subduction zone area that extends from the extreme northern part of California all the way to British Columbia.

Q: In the past couple years, there’s been a lot of work that’s been done by the United States Geological Survey (USGS) to try to develop an early warning system for earthquakes. Is the Department of Conservation involved in helping to inform the public if there is an earthquake?  

The Department of Conservation includes the California Geological Survey (CGS), which is modifying more than 70 of its existing seismic instruments to contribute to the early warning system. CGS has a statewide network of seismic monitors on dams, bridges, buildings and other structures – and also places some instruments underground – to gather earthquake shaking data that influence the state’s building code and help engineers building more earthquake-resilient buildings. Some of those instruments will also now be able to instantaneously provide the early warning system with data.

Q: How does the earthquake early detection system work?

When an earthquake occurs, the energy goes out from the epicenter in two different waves. The initial waves, P-waves, don’t typically cause much damage. Using instrumentation, scientists can immediately calculate the location and size (magnitude) of an earthquake from interpreting P-waves. The second waves – S-waves, which cause the shaking – follow several seconds after the P-wave. In that small amount of time between the P and S waves, the early warning system can give enough notice to allow people to take certain precautions: to duck under a table, or for a utility to shut down certain operations, or for a hospital to go to backup power, or for a train engineer to start braking.

In most cases, Californians are unlikely to get as much warning from this system as people in Japan and Mexico do. The major faults in those countries typically lie offshore, while those in California are much closer to major population centers.

Q: What can people do to prepare for earthquakes?

What people really need to know if this: If the earthquake is big enough and causes enough damage, you’re likely to be on your own for several days – no police, no fire department, no access to medical treatment, no city services, no quick trip to the grocery store or fast food place. There may not be running water, sewers, or power.

A lot of organizations, including ours, have information about how to prepare. Transportation corridors – freeways, railways, roads, etc. – may be blocked or packed with people trying to get out. So it’s up to you and your family to figure out how to get through the period, which may last up to a week before life starts to look even a little bit normal. You’ll need food and water, at least. Does anyone in your family take prescription medication? Do you have a battery powered radio to hear what’s going on? Do you have any cash on hand (the power and ATMs may be down)? If your family is separated at the time of a big earthquake, how would you reunite?

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