But, it is a theoretical risk, and, consequently, we thought the subject deserved a page on the site. To the right, you will see the most recent earthquake map from the US Geological Survey (web site: http://quake.usgs.gov/). As the map shows, there are very few major fault lines that run through the western part of San Diego County. There is the fault line that goes through the middle of La Jolla into San Diego. If you have never seen a fault line, you need only take one of the kayak tours into La Jolla Cove where it is easily visible from the water. We have not read any analysis as to what risk this poses for La Jolla or San Diego.

The large San Andreas fault that runs through San Francisco moves to the east and is the line by the Salton Sea (the blue on the right edge of the map). The bunch of magnitude 1 microearthquakes along the San Andreas fault that are constantly occuring along the major fault are not even felt along the coast.

One of the reasons why San Diego does not feel these quakes is because seismology experts say that the empirical data shows that the force of a quake moves along the fault line. Yes, some energy will be radiated in all directions. But, computer modeling shows that if a major quake occurs with a northbound direction, it will be Los Angeles which feels the effects of the quake, and Mexico if the quake moves southbound along the fault. While 50 years ago, scientists thought that the energy moved equally in all directions from the center of the fault, the research in recent years shows conclusively that this is not the case. This bodes very well for those of us in many parts of San Diego in the event that a major quake occurs along the San Andreas fault.

Risk is Relative
We cannot say that there is NO risk of a major earthquake in San Diego county. But a little perspective in comparing it to San Francisco will hopefully address any concerns that you may have. San Francisco sits on a number of major fault lines, and the USGS has concluded that:

On the basis of research conducted since the 1989 Loma Prieta earthquake, U.S. Geological Survey (USGS) and other scientists conclude that there is a 62% probability of at least one magnitude 6.7 or greater quake, capable of causing widespread damage, striking the San Francisco Bay region before 2032.

If you like maps and you want to further investigate the existence of small fault lines, the San Diego GIS site (www.SanGIS.org) has interactive maps with fault line information. You can zoom in and see where the fault lines line with respect to streets and neighborhoods.