The devastating earthquake that hit the heart of China in 2008 caught the region unguarded, and left tens of thousands of people dead.

Because the destruction was so widespread, many people witnessed the ground rip apart, which along with other observations and studies, is helping geologists piece together exactly what happened - and how to prevent future catastrophes.

The area of Wenchuan, China, was crippled by the 7.9-magnitude earthquake that struck on May 12, 2008. The temblor killed more than 70,000 people, injured about 374,000, and left approximately 18,000 missing and presumed dead, according to the U.S. Geological Survey (USGS). More than 45.5 million people across 10 provinces were affected by the quake. Four million people lost their homes. Several cities were almost completely destroyed.

Before the 2008 quake, the region was downgraded to a low seismic risk, so the massive temblor caught many scientists by surprise, which isn't uncommon even in areas known to have frequent earthquakes.

"Unfortunately, it's kind of a truism about the state of our knowledge that we're constantly surprised," said Ken Hudnut, a geologist with the USGS in Pasadena, Calif., who has studied the Wenchuan earthquake.

The most recent comparable earthquake in the area was between 1,000 to 2,000 years ago, suggests a study in the November edition of the journal Bulletin of the Seismological Society of America. The issue of the journal is a special one devoted to studies of the 2008 earthquake.