USGS logoCaltech, the USGS and the Earthquake Country Alliance presentCaltech logo

Northridge Earthquake 10th Anniversary

January 17, 2004
9 AM to 3:30 PM
At Beckman Auditorium on the Caltech Campus
Lectures, Movies, Displays and Activities about Earthquakes!

Just 10 years ago Los Angeles was shaken awake by the Northridge earthquake, and seismologists at the USGS and Caltech are still shaking things up with ground breaking research and state-of-the-art technology to better understand earthquakes and their effects.
Come and see what we have learned from the past and how we are planning for the future!

Activities and Resources
Caltech Campus Map
Download Flyer (PDF)
The Facts


Rupture Area:
Economic Loss:
Displaced from Homes:

January 17, 1994 4:31 PST
34 12.80'N 118 32.22'W
20 miles WNW of Los Angeles
1 mile SSW of Northridge
18.4 km
Northridge Thrust (also known as Pico Thrust)
300 km2
$20-$40 billion
57 people
20,000+ people

At 4:30 am, on January 17, 1994, residents of the greater Los Angeles area were rudely awakened by the strong shaking of the Northridge earthquake. This was the first earthquake to strike directly under an urban area of the United States since the 1933 Long Beach earthquake.

The earthquake occurred on a blind thrust fault, and produced the strongest ground motions ever instrumentally recorded in an urban setting in North America. Damage was wide-spread, sections of major freeways collapsed, parking structures and office buildings collapsed, and numerous apartment buildings suffered irreparable damage. Damage to wood-frame apartment houses was very widespread in the San Fernando Valley and Santa Monica areas, especially to structures with "soft" first floor or lower-level parking garages. The high accelerations, both vertical and horizontal, lifted structures off of their foundations and/or shifted walls laterally.

Despite the losses, gains made through earthquake hazard mitigation efforts of the last two decades were obvious. Retrofits of masonry building helped reduce the loss of life, hospitals suffered less structural damage than in 1971 San Fernando earthquake, and emergency response was exemplary. The Northridge earthquake proved that preparing for earthquakes can greatly reduce the risk.

The earthquake brought home several important lessons. Thrust faults concealed below Los Angeles present a threat to the region approaching that posed by the San Andreas fault. When earthquakes occur directly beneath a city, it will be subjected to ground motions with peak accelerations approaching the force of gravity, exceeding the levels of shaking anticipated by building codes. Systems of concealed faults under the Los Angeles area are more complex than previously thought. The significant fracturing of welds in steel frame buildings was unexpected because of the ductility of steel. Understanding the cause and correcting the problem will be essential to continue building in earthquake prone regions.

--SCEC Data Center