Whole Lot of Shaking Going On

California and San Francisco in particular are known for earthquakes because it straddles two tectonic plates, the North American and the Pacific which are separated by a large transform fault, the San Andreas Fault, which covers most of the coastline of California.  The Pacific Plate is moving north (LA is getting closer to San Francisco) and the tension built up from these plates causes earthquakes. Other faults extend from the San Andreas Fault. Most of the earthquakes cannot even be felt.  I remember reading in the newspaper as I was leaving San Francisco how many quakes there were during the week, more than 100, and I didn't feel any of them.  The news stations list the earthquakes over 2.0 on the richter scales as if it were rain or another weather event.  Although California has the reputation for them, Alaska actually has more earthquakes and more serious ones.

There have been 15 earthquakes ranging between 6.0 and 7.9 since 1800, but the 1906 San Francisco Earthquake clearly was the most significant. The earthquake occurred at 5:12 AM on April 18, 1906 and resulted in devastating fires which broke out and burned for four days.  More than 80% of the city was destroyed and it still ranks as one of the top disasters in the U.S.  The fires mainly caused by ruptured gas lines were actually responsible for about 90% of the damage. Although San Francisco rebuilt, the quake cause Los Angeles to be the dominant city in the state.

More recently, there was the 1989 Loma Prieta Earthquake during the World Series which caused a lot of property damage.  One of the lasting effects of that earthquake and a later one in Northridge is that the amount of seismic retrofitting has greatly expanded making buildings and other structures safer.  Fortunately we will be staying in a two story house while we are there.