Mexico's heaving seismic monster Tuesday, 26 September 2017

In the wake of the recent earthquakes that hit Mexico, damaging more than 3000 buildings, an unusual phenomenon has been witnessed on the capital’s streets.

Video has emerged of what shows asphalt rising up and then buckling in a heaving motion as if a large creature were underneath. The phenomenon appeared as a second earthquake rippled through Mexico City on 19 September, caused by what appears to be liquefaction. This occurs when saturated sand and silt turn liquid-like during an intense earthquake, and can trigger landslides and cause buildings to collapse.

Mexico City is built on a sediment basin, according to geophysicist Mika McKinnon, who said it was not that unusual following intense seismic activity. In the 14th century the area had a much more watery terrain, she explained, with an Aztec city (Tenochtitlan) built on an island. The area was later drained by the Spanish, trapping loose sediment that is still saturated with water along with pockets of air.

The recent quakes released built-up energy between the Cocos plate that carries the Pacific Ocean floor south of Mexico, and the North American plate which is to the north-east. While this is normal, many Mexicans are now asking how so many buildings collapsed and if this could have been avoided or mitigated. The government had introduced new building code regulations after an earthquake on the same day back in 1985 that killed 5000 people.

These regulations were updated in 1987, 1993 and 2003, according to the 13th World Conference on Earthquake Engineering in 2004, to reflect learnings from the mid-80s’ quake, and include technical innovations. But suspicions have been raised about unscrupulous builders and corrupt officials following the devastation from the recent seismic activity.

Of the 3000 reportedly damaged buildings from the recent quakes, 155 collapsed, 123 partially collapsed, 335 were severely damaged, and 1125 cracked, with some only completed months ago. Up to 300 people lost their lives as a result.


Image: Reuters via