he quake that shook Mexico City on Tuesday was a 7.4 magnitude.

It caused some damage but the effects were minor compared to the Mexico quake in 1985 that killed some 10,000 people.

Anchor Lisa Mullins speaks with Paul Caruso, a geophysicist at the National Earthquake Information Center, about why this earthquake was so much less deadly.

Caruso says that the 1985 quake was devastating because of liquefaction — when buildings are built on sand an earthquake makes the ground become like liquid.

“I have a picture of a building, where the third floor of a building had crushed a car in San Francisco because the ground had liquefied under that building.”