Af­ter Mex­ico City quake, big struc­tural risk re­mains

En­gi­neers urge of­fi­cials to quickly iden­tify and retro­fit weak build­ings

Los Angeles Times - - NEWS - By Rong-Gong Lin II and Ce­cilia Sanchez ron.lin@la­times.com Twit­ter: @ron­lin Times staff writer Lin re­ported from Los Angeles. Sanchez is a mem­ber of The Times’ Mex­ico City bureau. Staff writer Kate Linthicum in Mex­ico City con­trib­uted to this re­port.

MEX­ICO CITY— Cer­tain types of build­ings are es­pe­cially vul­ner­a­ble to col­lapse dur­ing earth­quakes — and earth­quake­prone Mex­ico City is filled with them.

Those with so-called brit­tle con­crete frames are well-known haz­ards. Build­ings with a weak first story, of­ten sup­ported by nar­row col­umns to ac­com­mo­date park­ing, are also known to be dan­ger­ous.

How many such build­ings ex­ist in this 573-squaremile me­trop­o­lis, home to nearly 9 mil­lion peo­ple, is hard to know. The gov­ern­ment has never cat­a­loged its real es­tate to iden­tify risky struc­tures.

Now, in the wake of the mag­ni­tude 7.1 earth­quake that killed more than 360 peo­ple in Septem­ber, some ex­perts are urg­ing city of­fi­cials to do just that — so ten­ants can be warned and build­ing own­ers can be or­dered to retro­fit them with steel braces or new walls.

“We have to move very fast,” while the is­sue is fresh in peo­ple’s minds, said Ser­gio Al­co­cer, an earth­quake ex­pert at the In­sti­tute of En­gi­neer­ing at the Na­tional Au­ton­o­mous Uni­ver­sity of Mex­ico.

Such an un­der­tak­ing is costly and has long been viewed as po­lit­i­cally dif­fi­cult. Many cities have re­sisted sim­i­lar calls.

But po­lit­i­cal sen­ti­ment can shift. In 2015, Los Angeles be­came the big­gest city in Cal­i­for­nia to pass a law to iden­tify vul­ner­a­ble con­crete build­ings and apart­ments with weak ground sto­ries and man­date retrofitting. Once build­ing own­ers are no­ti­fied, they have seven years to fix weak ground sto­ries and 25 years to com­plete mod­i­fi­ca­tions to sta­bi­lize brit­tle con­crete frames.

In an interview, Los Angeles Mayor Eric Garcetti en­cour­aged Mex­ico City to start now.

“Wait­ing causes lives to be lost,” he said.

Los Angeles an­tic­i­pated or­ga­nized op­po­si­tion by build­ing own­ers and over­came it by con­duct­ing two years of pub­lic ed­u­ca­tion ef­forts on the risks of in­ac­tion.

But Mex­ico City hasn’t had that level of dis­course, and there is an ex­pec­ta­tion that own­ers would also op­pose manda­tory retrofits. Al­co­cer, who is a mem­ber of a may­oral com­mis­sion es­tab­lished to make rec­om­men­da­tions for the city’s long-term seis­mic re­siliency ef­forts, said he imag­ined of­fer­ing own­ers eco­nomic in­cen­tives such as waiv­ing prop­erty taxes or eas­ing the fi­nan­cial bur­den with city loans or bonds.

In Cal­i­for­nia, retrofits of smaller apart­ment build­ings typ­i­cally cost tens of thou­sands of dol­lars, while strength­en­ing taller build­ings can ex­ceed $1 mil­lion.

Al­co­cer es­ti­mated that the cost of retrofits in many cases would be 15% to 20% of the cost of re­plac­ing a build­ing.

A to­tal of 42 build­ings col­lapsed and as many as 1,000 more were dam­aged in the Sept. 19 earth­quake that was cen­tered about 80 miles south­east of Mex­ico City.

Many of the build­ings that fell were made of brit­tle con­crete, in­clud­ing a sev­en­story of­fice build­ing on Avenida Al­varo Obre­gon in Mex­ico City, where 49 peo­ple died — the largest death toll at any one site.

That build­ing was a “flat slab” struc­ture, a de­sign that lacks hor­i­zon­tal beams that are far more durable in an earth­quake. Flat slab con­struc­tion was very pop­u­lar in Mex­ico City in the 1960s and ’70s, Al­co­cer said.

“This sys­tem is not a proper sys­tem for a high seis­mic area,” he said.

Retro­fit­ted build­ings sur­vived just fine in the earth­quake.

“We have the pre­scrip­tion,” said Saif Hussain, a Los Angeles-based struc­tural en­gi­neer who vis­ited Mex­ico City in Oc­to­ber with the Ap­plied Tech­nol­ogy Coun­cil, which de­vel­ops na­tion­ally rec­og­nized retro­fit stan­dards. “It’s just a mat­ter of peo­ple be­ing aware of it, and im­ple­ment­ing it — and the po­lit­i­cal will.”

Al­co­cer said he re­cently met with Mex­ico City’s mayor, Miguel An­gel Mancera, and sug­gested the city make a plan to re­view and even­tu­ally strengthen cer­tain classes of build­ings known to be haz­ardous, as well as eval­u­ate all schools, hos­pi­tals and mar­kets. “He’s very open to it,” Al­co­cer said.

The mayor’s of­fice did not re­spond to interview re­quests.

Mex­ico City res­i­dents said in in­ter­views that they would wel­come new safety mea­sures. But many doubted that the gov­ern­ment had the po­lit­i­cal will to even con­duct a cen­sus of build­ings, let alone or­der costly im­prove­ments.

“I think the gov­ern­ment should tell us if the area is safe, if our build­ing could be in dan­ger if they do not make the right re­vi­sions,” said Clau­dia Cen­teno, a 40-year-old nurse who was told that the dam­age to her apart­ment was only cos­metic.

“I’m go­ing to leave this build­ing as soon as my rental agree­ment is up, but the next peo­ple who want to live here may be at risk and might not know if the gov­ern­ment says noth­ing,” she said.

Af­ter the quake, city in­spec­tors fanned out to as­sess the dam­age. But they were not check­ing for vul­ner­a­bil­ity to the next earth­quake, ac­cord­ing to El­iz­a­beth Cochran, a U.S. Ge­o­log­i­cal Sur­vey seis­mol­o­gist who re­cently vis­ited Mex­ico City with the Earth­quake En­gi­neer­ing Re­search In­sti­tute as part of a mis­sion to learn from the Septem­ber earth­quake.

Rosario Aven­daño, a 22-year-old mar­ket­ing stu­dent whose apart­ment build­ing in the Del Valle neigh­bor­hood is still stand­ing, al­beit with cracks in some walls, said she wants the gov­ern­ment to con­duct more thor­ough as­sess­ments.

“The gov­ern­ment is only cov­er­ing the sun with a fin­ger,” she said. “They are go­ing to re­model, they are go­ing to paint, they are go­ing to change bro­ken glass so that ev­ery­thing looks nice again, but they are not do­ing in-depth stud­ies of why so many build­ings were dam­aged in the city.

“The gov­ern­ment must tell us the truth about whether or not our houses are safe.”

Gary Coron­ado Los Angeles Times

THE MAG­NI­TUDE 7.1 earth­quake on Sept. 19 killed more than 360 peo­ple in and around Mex­ico City.

Michael Owen Baker For The Times

BUILD­INGS with first sto­ries sup­ported by col­umns, like these apart­ment com­plexes in Santa Mon­ica, tend to be vul­ner­a­ble to col­lapse in an earth­quake.

Rong-Gong Lin II Los Angeles Times

MORE PEO­PLE died at the site of this build­ing in Mex­ico City — 49 — than any other in the Septem­ber quake. The struc­ture was made of brit­tle con­crete.

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