1987 Whittier Narrows earthquake

The 1987 Whittier Narrows earthquake happened in the southern San Gabriel Valley and nearby areas of Southern California on October 1 at 7:42 a.m. It was a moderate magnitude 5.9 blind thrust earthquake centered north of Whittier in Rosemead. The earthquake had a shallow depth and was felt across southern California and southern Nevada.

Many homes, businesses, and roads were damaged, especially in Los Angeles and Orange counties. Damage costs were between $213–358 million, and there were injuries and a few deaths connected to the earthquake. The strongest shaking was in Whittier, where the historic uptown area saw the most damage.

Three days later, another smaller earthquake happened nearby, causing more damage and one additional death. Because many buildings in the Los Angeles Metropolitan area had special equipment to measure shaking, scientists were able to study this earthquake and learn more about how earthquakes behave in Southern California.

Tectonic setting

See also: Fold and thrust belt, Los Angeles Basin, and Southern California faults

Starting with the 1983 Coalinga earthquake, people began to understand more about hidden faults in the earth. The 1987 Whittier Narrows earthquake happened on a hidden fault that was not known before, now called the Puente Hills thrust system. Scientists learned about this fault by studying the earthquake and its smaller shakes. They found that this fault runs from downtown Los Angeles to near Puente Hills. Because it is close to many people and could cause strong shaking, this fault is considered very important to watch.

Past seismicity

In 1929, another earthquake happened in Whittier on July 8. It was not as strong as the 1987 earthquake but still caused damage. Some buildings, like a school and homes, were heavily damaged, and other homes had their chimneys fall down. The shaking was felt from Mount Wilson to Santa Ana, and from Hermosa Beach to Riverside. After this earthquake, there were many smaller shakes that continued for a few years.

Earthquake

The main earthquake happened close to the edge of Puente Hills, a little north of Whittier Narrows. It was 14 kilometers deep. Scientists studied the shaking and found that it came from a fault that pushes rocks upward.

The earthquake was strong, especially in Whittier, where older buildings were damaged. It was the biggest shaking in the Los Angeles area since the 1971 San Fernando earthquake. People felt it far away, from San Diego to Las Vegas. Some roads closed because pieces of concrete fell off, and a few people were hurt. Many homes were destroyed or damaged in Los Angeles, Orange, and Ventura counties.

Scientists recorded the shaking using special tools placed around the area. These tools showed that the strongest shaking lasted just a few seconds. The earthquake had smaller shakes after it, called aftershocks. One big aftershock happened three days later and caused more damage, breaking windows and damaging buildings.

Aftermath

After the earthquake, the city of Whittier created a large area to help with rebuilding. This area allowed the city to use property taxes for recovery efforts until 2037.

A group called the Whittier Conservancy formed to help protect the city's historic buildings. During the earthquake, some old buildings were destroyed, including the Harvey Apartments. These buildings used special bricks made by hand in the 19th century from the San Gabriel River. The Conservancy saved these bricks to use in rebuilding, spending money to keep them safe. They also helped plan changes in the Hadley neighborhood and managed new home construction.