15. California

California is one of the highest risk states in the United States for earthquakes. The San Andreas fault runs almost the entire length of the State in a northwesterly trend. Although a devastating earthquake hit San Fransisco in 1989, it is believed that a much bigger earthquake (dubbed "the big one") is due to strike California along this fault (1). The Los Angeles area is especially vulnerable as it has not had a major earthquake in over 120 years There was a large earthquake in Reseda, California (part of Los Angeles county) on Jan 17th, 1994 (aka the "Northridge Earthquake") but it was along the previously undiscovered Northridge bind thrust fault. Below is a map of California highlighting the earthquake risk areas(2).

The San Andreas fault is part of a series of faults which creates a circle around the Pacific Ocean called the "Ring of Fire." In the last two years there have been three major earthquakes on three corners of the ring of fire. Last March, 2011, a 9.0 struck Northern Japan with a subsequent tsunami killing over 13,000 people. In February of 2011, a quake toppled Christchurch, New Zeland. In 2010 an 8.8 quake struck Chile (3). If you look at the map below, that leaves only one area missing, the Northeastern corner of the ring of fire. Many believe this area is now due for a giant earthquake in the not too distant future.

Portland, Oregon is also part of the ring of fire and the area which is believed to have the next big quake. In recent history, Oregon has not had many earthquakes like its southern neighbor California. For this reason, many experts are scared that if a big one does happen, the unpreparedness of Portland, and other major cities in Oregon, will lead to a major catastrophe and loss of life.

1. Stephen S. Birdsall. Regional Landscapes of the United States and Canada
2. http://en.wikipedia.org/wiki/Pacific_Ring_of_Fire
3. http://www.huffingtonpost.com/2011/03/16/california-earthquake_n_836594.html