Earthquake Experts Urge Acceleration of California Retrofitting Requirements

by Zelle LLP

On September 19, 1985, more than 5,000 people in and around Mexico City lost their lives when the 8.0 magnitude Michoacán earthquake collapsed 412 buildings and seriously damaged several thousand more. Many of the buildings that collapsed were older structures built of unreinforced masonry. But newer multi-story buildings built of reinforced concrete actually fared the worst.

On September 19, 2017 – 32 years to the day after the Michoacán quake – the 7.1 magnitude Puebla quake struck Mexico City, claiming 369 lives and collapsing 46 buildings. Immediately after this year’s quake, a team of engineers from the John A. Blume Center for Earthquake Engineering at Stanford University fanned out across the city to figure out what the collapsed buildings had in common.

The Mexico City quake raises concerns about construction in other areas.

The Stanford team recently published their preliminary report, and their findings sound an alarm not only for Mexico City, but also for California and other areas. Most of the structures that collapsed in the Puebla quake this year were multi-story, reinforced concrete buildings that should have been retrofitted or condemned long ago. Also, 57 percent of the collapsed buildings had what engineers call a “soft story” – an open floor plan at the ground floor, often used to create parking space, below a structure supported on columns. 

photo: google street view   



SOBERING SIGNALS IN MEXICO CITY. These photos show the same apartment building before and after the Puebla earthquake struck on September 19, 2017. Earthquake experts say similarly designed buildings are common in California, and retrofitting projects there should be accelerated.

The risks are known, but they’re hard to fix.

Flat slab construction supported by reinforced concrete columns has long been identified as vulnerable to seismic activity, especially when buildings are constructed with a soft story at ground level. Building codes in Mexico City and elsewhere have evolved away from this type of construction, and existing buildings can be made safer with seismic retrofitting. But as building officials south of the border can attest, compelling thousands of building owners to retrofit their buildings is no easy feat. And their colleagues north of the border need look no further than their own backyards. The same design is still common in San Francisco, Oakland, Santa Monica, Los Angeles, and other earthquake-prone parts of the U.S. And despite the design’s poor performance in the 1989 Loma Prieta and 1994 Northridge earthquakes, retrofitting is moving too slowly to ensure that the next California earthquake won’t lead to widespread damage and casualties.



ECHOS NORTH OF THE BORDER. These photos show buildings with soft first floors that collapsed in the 1994 Northridge quake in Los Angeles (left), and the 1989 Loma Prieta quake in San Francisco (right). In the photo at left, parked cars can be seen crushed by the building where the soft first floor created parking space.

Building code changes are not enough.

After the 6.7 magnitude Northridge quake killed 57 people in 1994, Los Angeles beefed up the seismic requirements of its building code. San Francisco had taken similar steps years earlier, after the Loma Prieta earthquake in 1989. But changes in the building codes only improve construction standards by attrition, as old buildings are replaced with new ones. Los Angeles, San Francisco, and other cities have launched programs requiring owners to retrofit existing buildings deemed vulnerable to seismic activity. Still, progress has been slow, with pushback from building owners burdened by the cost, and tenants worried about shouldering higher rents. 

DANGER ZONE. This map developed by Los Angeles building officials shows apartment and condominium buildings that are still likely in need of seismic retrofitting, despite building code changes and retrofitting initiatives introduced more than two decades ago.

Retrofitting for the next big quake.

In 2014, the Los Angeles City Council was so frustrated with the slow pace of retrofitting progress that it instructed building officials to go door to door, identifying apartment buildings vulnerable to collapse in the next temblor. After two years gathering the data, the Los Angeles Department of Building and Safety (LABDS), released the addresses of about 13,500 soft story buildings that may be at risk, and LABDS now provides information on the retrofitting status of buildings through its permit and inspection website. San Francisco launched a similar program in 2013, and interactive maps maintained as part of the city’s Mandatory Soft Story Program provide access to records on thousands of at-risk buildings in the city.

A bitter reminder of too little, too late.

Building officials and engineers agree that building codes governing new construction are critically important, but they do nothing to make older buildings safe. The Puebla quake provided a bitter reminder of that fact. When the quake struck on September 19, it came just hours after events commemorating the 1985 Michoacán earthquake, and those events included earthquake safety drills. The hard lessons of this year’s Mexico City quake are clear: new buildings codes are not enough, and retrofitting is moving too slowly to keep people and property safe from the next earthquake. That lesson is being heard loud and clear in California, where officials continue to push ahead with retrofitting efforts. How much progress they will make before the next big temblor remains to be seen.



DISCLAIMER: Because of the generality of this update, the information provided herein may not be applicable in all situations and should not be acted upon without specific legal advice based on particular situations.

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