After the Ridgecrest Earthquake: A Reminder for All of Earthquake Country

After the Ridgecrest Earthquake

A Reminder for All of Earthquake Country

The recent earthquakes near Ridgecrest, California, are clear reminders.  Lessons learned in earthquake country are familiar:  landslides, gas and water main breaks, structure fires, power outages, and closed highways.  In many offices, libraries, stores, and households, shelves emptied and furniture toppled.  Nerves frayed.

“Nothing that happened in Ridgecrest was really a surprise to the geoscientists, engineers, and emergency managers who do this for a living,” according to Eldon Gath, a southern California geologist who specializes in earthquake hazards.

Other parts of earthquake country should pay attention to Ridgecrest.  This includes all of California, the Pacific Northwest, Alaska, Hawaii, and most of the region west of the Rockies.  Most of these areas at least recognize their earthquake hazards exposure.  Many have some preparations in place.  But other parts of the US are not as well informed.

Some areas east of the Rockies have large earthquakes in their past, too.  The New Madrid region of Missouri, Arkansas, Kentucky, and Tennessee had a series of large earthquakes in 1811-12.  This is very recent in geologic time.

Central Oklahoma and central Kansas have an ongoing earthquake history.  Ohio, South Carolina, Massachusetts, Indiana, Alabama, Illinois, Virginia, and Texas all have their areas of known and significant earthquake hazards.

“The central and eastern US are especially vulnerable to earthquake hazards,” says Dr. Briget Doyle from the University of South Carolina Upstate.  “Earthquakes just aren’t in most folks’ personal experience, so they don’t think about them much.”

These earthquakes in Ridgecrest were large.  On Thursday, July 4, a magnitude 6.4 occurred, located just 11 miles away.  About 34 hours later, a magnitude 7.1 happened, also 11 miles from Ridgecrest.  This put the city of almost 30,000 between two of the largest earthquakes to hit southern California in 20 years.  Both were shallow, which means shaking at the surface was more intense.

 Considering the size of these earthquakes, and the damage they could have done, Ridgecrest was favored.  There was one apparent fatality, and few injuries.  Damage was costly, but mostly fixable.  As bad as it was, it could have been much worse.

Ridgecrest also was prepared for earthquakes, which stacked the deck in its favor.  Some of that preparation was due to the statewide building code that California adopted in 1933.  This came after vivid damage to schools in the 1933 Long Beach earthquake.  More came from timely updates to that building code.  They included new lessons learned from later earthquakes.

Other factors may be more luck.  The majority of structures in the region are one-story, wood-frame construction.  These are more flexible that other structure types.  As unnerving as it is to ride out an earthquake inside, wood-frames flex and absorb the earthquake energy better than stiffer structures. 

Most of Ridgecrest’s structures have been built after 1940 – fairly young, as cities go.  So most of its construction was built to post-1933 building codes.  There are no unreinforced masonry structures in the region – zero brick and stone.  Those unreinforced masonry structures are most vulnerable to earthquake damage and loss of life.  In earthquake country, brick or stone buildings are best avoided.

Finally, the Ridgecrest area is a desert.  This means that liquefaction, which needs a shallow water table, is unlikely.  And the local topography is fairly flat, so landslides and rockfalls did not directly affect the city.  Some local highways had minor rockfall damage, but make-do repairs had the roads open fast.

Overall, Ridgecrest fared well through these earthquakes because of planning and luck.  Many other areas of earthquake country don’t yet have enough preparedness planning.  And they shouldn’t rely on luck.  The most important lesson learned from Ridgecrest is “Are you ready?” 

You can stack that deck in your favor by anticipating earthquake effects in your area.  Then take action to prevent future damage.  And, with planning and luck, your little slice of earthquake country may be able to remind the next generation of earthquake anticipators of even better steps they can take.

 

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AEG is the premier professional society in the applied fields of environmental and engineering geology.  Members provide significant public contributions to the communities in which they work, enhancing public safety, protecting property and contributing to economic vitality. Environmental and Engineering Geologists play a vital role in the identification and mitigation of geologic and seismic hazards and environmental impacts to soil, surface water and groundwater, and dealing with the aftermath of hurricanes, tropical storms, torrential rains, landslides, earthquakes and other natural catastrophic events. 

For more information, visit www.aegweb.org, the website of the Association of Environmental & Engineering Geologists.

 

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