3.2 to 7.1 Magnitude Earthquake Hits Mexico

By: Victoria Ifatusin

Two military men standing in front of a leaning destructive building (Angel Hernandez / EPA)

The convulsion left over 300 people dead and about 6,000 injured.

On September 19,  an estimated 7.1 earthquake struck Central Mexico, shaking for 20 seconds. It was centered at about 34 miles south of the city of Puebla.

Mexico is known to be one of the world’s most seismically active regions, prone to receiving earthquakes. It sits on top of several intersecting tectonic plates.

Mexico City lives on a dry lakebed with soft soil that is made up of sand and clay, which intensifies the destruction that earthquakes cause.

Loose sediments near the surface usually slows the shock waves’ speed from 1.5 miles per second to about 150 feet per second. It expands the shock waves amplitude, which causes more violent shaking. Deeper and denser soil layers increase volume shock waves’ destructive duration.

Before the Puebla earthquake, an earlier earthquake hit Mexico in Chiapas on September 7, killing about 100 people.

There is a possibility of a link between the earthquakes, which was being scrutinized in the days after the latter.

These earthquakes can cause a long-term risk of seismic activity.

During the Central Mexico earthquake, that static stress transfer was considered dubious due to the distance between the earthquakes.

According to the National Seismological Service (SSN) of Mexico, the epi-center was located 12 km, southeast of Axochiapan, Morelos, and 120 km from Mexico City.

The earthquake was measured at a magnitude of 7.1, occurring at 1:14 p.m. Central Time, at a depth of 51 km.

The United States Geological Survey (USGS) placed the epi-center 5 km of San Juan Raboso and reported a measurement of “severe” on the Mercalli intensity scale.

There was a report of strong shaking for a minute, which is a long time for earthquakes.

According to the United States Geological Survey, the earthquake occurred on a dipping normal fault.

An advance warning was given in Mexico City, although, the general experience in the capital was that the alarm and cellphone alerts started only a few seconds before the earthquake.

Some residents mistook the alert for a continuation of the earlier drill.

Nine days after the earthquake, it was reported that at least 361 people had died.

Up to seventy-four people were killed in the state of Morelos, 220 in Mexico City, forty-five in Puebla, thirteen in the State of Mexico, six in the state of Guerrero and one in the state of Oaxaca.

In Mexico City, there were bodies of twenty-six students and four instructors that were pulled from the rubble of the Enrique C. Rébsamen School.

The Mexico City campus of the Monterrey Institute of Technology and Higher Education suffered damage, with at least five people killed and forty injured.

More than 6,000 people had been reported injured by the day after the earthquake, with over 295 confirmed dead.

September 19 is known as a day of remembrance for the 1985 Mexico City earthquake, which killed approximately 10,000 citizens.

Every year at 11 AM, a national earthquake drill is conducted by the government with the use of public loudspeakers located throughout Mexico City.