Cancun, Q.R. — September has proven the most volatile month in parts of Pacific Mexico with the National Seismological Service (SSN) announcing a record number of earthquakes.
SNN reports that during the month of September, they have recorded the highest amount of earthquakes so far this year with 5,735. As of October 24, SNN says that the Institute of Geophysics of the National Autonomous University of Mexico (UNAM) has registered 8,678 tremors with magnitudes that have ranged from 1.3 to 8.2 throughout Mexico.
They add that on average, Mexico experiences 40 earthquakes per day, which they say is not uncommon for the country.
A generous portion of Mexico is located on three large active tectonic plates, making it one of the world’s most seismically active regions. It is the relative motion of these plates that cause frequent earthquakes and the occasional volcanic eruption.
Most of the Mexican landmass is on the westward moving North American plate, however the Yucatan Peninsula, including the regions of Cancun and down into Riviera Maya and beyond, are on a completely separate land bridge of the Caribbean Plate.
John Bellini, a geophysicist with the US Geological Survey says the September Mexico quakes originated on a fault within the Cocos plate on Mexico’s western edge. “Whether or not faults rupture depends on the kind of stress that builds up,” Bellini says.
The Cocos plate scoots rapidly under the continental crust of the North American plate, which “builds up the stress and strain at a faster rate, so you’re liable to have more frequent earthquakes because of that,” he explains.
Mexico City is especially prone to severe damage because of the ground it sits on, which is an ancient lake bed that quivers like jello, Bellini says. When earthquake waves pass through it, it jiggles, magnifying the vibrations.
“So the reason that Mexico City seems susceptible to more damage is because of this amplification effect of the lake bed,” Bellini notes.
However, the contrary is true for the Caribbean Sea side of Mexico where soil from the Yucatan Peninsula south makes the entire region a non-seismic zone. Francisco Poot, Cancun engineer, says that the subsoil of Cancun, Playa del Carmen and the entire Riviera Maya is made of limestone, which has great rigidity.
Mexico has a long history of destructive earthquakes and volcanic eruptions. In September 1985, a magnitude 8.0 earthquake killed more than 9,500 people in Mexico City. In southern Mexico, Volcán de Colima and El Chichón erupted in 2005 and 1982, respectively.
Popocatépetl and Ixtaccíhuatl volcanos southeast of Mexico City, occasionally vent gas that can easily be seen from the City, a reminder that volcanic activity is ongoing. Popocatépetl volcano last erupted in 2010.