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Expert: Mexico City continuing to shrink, cracks more frequent
[January 01, 2011]

Expert: Mexico City continuing to shrink, cracks more frequent

Mexico City, Jan 1, 2011 (EFE via COMTEX) -- Mexico City has areas that have sunk dozens of feet in a little more than a century and cracks caused by overexploitation of underground aquifers are increasingly frequent, a National Autonomous University of Mexico, or UNAM, scholar said.

Because of their size, the fissures "are generating alarm among the population and even causing significant damage to buildings and (affecting provision of) public services," Gabriel Auvinet Guichard, a researcher at UNAM's Engineering Institute, said Friday.

Intensive extraction of water from deep wells in the Valley of Mexico - where the country's massive capital lies - is responsible for the most serious cracks, the expert said.

According to information Auvinet has gathered at UNAM's Geoinformatics Laboratory, the parts of the valley most affected by this phenomenon are Iztapalapa, Chalco, Xochimilco, the areas bordering the Santa Catarina mountain range, Xalostoc and Vallejo.

Some portions of the Valley of Mexico have sunk by 13 meters (42 feet) since the end of the 19th century, the geotechnical engineer said, adding that this "has affected transition zones and resulted in differential settling and cracks, which have caused considerable damage and even accidents in residential areas." The fissures damage buildings, highways, roads and public infrastructure - including the potable water distribution network, which has a severe leaky-pipes problem - and exact a heavy financial toll on the capital.

Auvinet and other experts have created a database to track the location of the cracks, which they classify by the mechanism that caused them; construction companies will have to use maps based on that information in meeting building code requirements.

"The database contains 380 records of fissured zones; however, it's a big problem and there's much more to do," he said.

Through his research, Auvinet has determined that Mexico City's cracks "are not distributed haphazardly" but instead are mainly concentrated in certain areas.

"It's also been shown that there's no correlation between them and tectonic activity," he added.

The cracks, which are up to 22 meters (72 feet) deep and 30 meters long and have even caused fatalities in Mexico City, "must be fixed immediately to avoid an even bigger problem," the engineer said.

"They must be filled as soon as possible," he said, adding that sand is the best material to use because it helps control erosion.

EFE jd/mc

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