LOS ANGELES – Twenty-six years ago, a violent pre-dawn earthquake woke Angelenos, and dawn revealed widespread devastation, with dozens killed and $ 25 billion in damage.
Here we present a look at the past that shows us the damages, deaths and the evolution in seismic safety since the disaster:
On January 17, 1994, at 4:31 a.m., a hidden fault lurking beneath neighborhoods in the San Fernando Valley unleashed a 6.7 magnitude earthquake that ripped apart buildings, ruptured water pipes and started fires.
The so-called blind thrust fault, with no surface features to reveal its presence, caused a block of earth to move upward. Most of the energy was released toward the mountains that line the north side of the valley, but more than enough energy was sent in other directions to cause devastation.
The earth shook horizontally and vertically for up to 10 seconds, most strongly in an area 30 miles (48 kilometers) in diameter around the Northridge neighborhood in Los Angeles, according to the public-private partnership Earthquake Country Alliance.
It felt as far away as Las Vegas.
State authorities reported that at least 57 people died in the earthquake, although a study published the following year put the death toll at 72, including heart attacks. About 9,000 people were injured.
The highest concentration of deaths occurred in Northridge Meadows, a 163-unit apartment complex where 16 people died when it collapsed in the lower parking area, crushing first-floor apartments.
The Northridge Meadows catastrophe revealed a particular seismic hazard due to so-called soft-story construction in which the ground level of a building has large open areas for purposes such as parking spaces or storefronts.
Northridge Earthquake: A Look Back In The First Hours After The Earthquake.
Widespread damage to buildings, highways, and infrastructure made Northridge the costliest disaster in America at the time.
According to the Earthquake Country Alliance, 82,000 residential and commercial units and 5,400 mobile homes were damaged or destroyed, nine parking lots were torn down, nine hospitals were evacuated due to structural or other problems, seven key highway bridges collapsed and hundreds more were damaged.
Some 200 tall elevations of steel frame suffered cracked fissures.
The vivid images of the earthquake included scenes of vehicles stranded high up on an elevated section of the highway, with the road falling ahead and behind, and the wrecked motorcycle of a police officer who rushed to his death at the end of a broken overpass as he rushed to work in the early morning darkness.
The California Department of Transportation, which had already modernized many of the bridges that were damaged, would spend hundreds of millions of dollars to further strengthen the many bridges identified as at risk.
The damage to hospitals led the state to demand the strengthening of those buildings.
The Great Shake Out can show you how to protect yourself in the event of an earthquake.
Changes since the earthquake
Since Northridge, there has been a push for progress, sometimes frustratingly slow, in everything from making buildings safer to increasing society’s overall ability to cope with seismic hazards.
Annual earthquake protection drill: In 2008, an annual earthquake drill known as the Great ShakeOut began in Southern California to teach the basic safety technique of “drop, cover, and hold on.” Based on a 7.8 magnitude earthquake scenario at the southern tip of the mighty San Andreas fault, the drill has spread across the United States and around the world.
Mandatory Modification Ordinance: In 2015, Los Angeles enacted a mandatory modification ordinance for the city’s most vulnerable buildings aimed at preventing loss of life in major earthquakes. It covered approximately 13,500 “soft-build” buildings like Northridge Meadows and about 1,500 “non-ductile reinforced concrete” buildings.
The ordinance, however, allowed a process that spanned seven years for the modernization of soft-story buildings and 25 years for non-ductile reinforced concrete buildings.
How to prepare for an emergency
Evolution of the failure model: Researchers can better document faults in the Los Angeles area, what seismologist Dr. Lucy Jones called a “CAT scan” of the Los Angeles basin. The models allowed the researchers to study the Oakridge fault, a larger fault that appears in Ventura County.
Best highway overpasses: A large investment in overpass modernization means those structures should be better able to withstand an earthquake. But it is not the same for all bridges.
Early warning system: Last year, the U.S. Geological Survey announced that its new West Coast earthquake early warning system was ready for wide use by businesses, utilities, transportation systems, and schools after years of development and testing. of prototypes.
A new app will alert Angelenos to tremors and earthquakes in the area.
The system detects the onset of an earthquake and sends alerts that can issue warnings from several seconds to a minute before the earthquake hits, depending on the distance from the epicenter. That time may be enough to slow trains, stop industrial processes, and allow students to crawl under desks.
Los Angeles Early Warning App: This month, Los Angeles Mayor Eric Garcetti revealed a mobile app that uses the early warning system to alert Los Angeles County residents when there is an earthquake of magnitude 5.0 or greater. Other mobile applications are in development.
The Los Angeles Economic Development Corporation also published a guide aimed at helping businesses minimize disruptions caused by major earthquakes, leveraging information technologies like the digital cloud to keep a business running even if its physical systems are destroyed or damaged. inaccessible.