Past Earthquakes Give Clues to Future

Earthquake awareness month ends with a reminder of the devastation the shakers can cause by looking into the past to help understand the future. And, with the Sierra Madre Fault line running through the San Gabriel Mountains, Crescenta Valley would do well to become familiar with quakes and understand that one striking here could cause destruction of property, if not loss of lives.

At 5:12 a.m. on April 18, 1906 San Francisco was destroyed by a 7.9 earthquake. In accounts of the quake people spoke of the ocean being pulled back, the sand shifting under their feet and buildings almost bending before crashing to the ground. It x still represents one of the most significant earthquakes on record.

Although the earthquake was devastating it actually helped scientists in the study of future quakes.

"It taught us so much about earthquakes," Andrea Donnellan, JPL geophysicistand a research professor at the University of Southern California, said.

The fact is a large earthquake is going to hit California. La Cañada and Crescenta Valley's granite foundation may have less destruction than sandy Santa Monica, but that will depend on where the earthquake begins.

"It can be a 7.2 to 8.3," Donnellan said. That magnitude would affect the state ? the 1906 quake ruptured a fault about the third of the way down California, Donnellan added.

If a high magnitude earthquake strikes the Sierra Madre Fault, the area would be devastated, she said.

Donnellan hopes that through her work, city and government officials will be able to know where an earthquake will hit and its strength.

"We measure all the quiet motions that occur between the earthquakes. The ground is always moving," Donnellan said. The pressure is building. "The longer it takes to happen the bigger it is going to be. They [the government and individuals] need to have a plan."