World

Major Quakes Rock Mexico

Here’s what two in one month mean

For the second time in two weeks, a powerful earthquake struck Mexico.

Although the two quakes hit hundreds of miles apart, experts say they have some similarities.

1.
The quakes are on the edge of the North American Plate, a major fault line.

US Geological Survey

When fault lines rupture, they can chain and trigger fissures at other locations along the plate’s edge.

Ronaldo Schemidt/AFP/Getty Images

2.
The Mexican capital is especially at risk because it is built on soft, wet ground that was once a lakebed.

US Geological Survey

The Mexico City earthquake struck at a depth of about 33 miles (51 km), making it a shallow quake. These types of quakes often cause the most damage.

Alfredo Estrella/AFP/Getty Images

3.
Both quakes occurred in the so-called Pacific Ring of Fire, one of the most seismically active zones on the planet. About 80% of all earthquakes strike there.

US Geological Survey

Five tectonic plates — Cocos, Pacific, Caribbean, Panama and North American — collide in central and southern Mexico, making the region one of the most unstable.

Yuri Cortez/AFP/Getty Images

Aftershocks can happen minutes, days, or months after the main quake hits, but the second quake in Mexico City is probably not an aftershock. Its epicenter was too far from the first quake’s.

Ronaldo Schemidt/AFP/Getty Images

... significant stored energy has been released from the ground, which means that the likelihood of much larger earthquakes in the region has reduced now.

Araceli Padilla

Associate professor of geotechnical and earthquake engineering at the University of Technology Sydney