Populations at Risk of High Magnitude Earthquakes in California

Background Information

California is a geologically active state do to its proximity to and containment of the San Andres fault, a transform fault.  This geologic activity presents varying levels of  risk to different populations.  This study focuses on Hispanic populations, and individuals below poverty level.  Earthquake data used for this map was downloaded within five years of the 2000 and 2010 Censuses; rated a magnitude three or above on the Richter Scale.

Data Sets

• 2000 Census Data, American Fact Finder
• 2010 Census Data, Tiger Products
• USGS Earthquake Archives

Methodology

To obtain earthquake frequency per county, points of earthquake occurrences were layered on top of county level Census data, then joined to their associated county using ArcGIS 10.1. In order to evaluate the earthquake risk level on the selected populations, the number of people per population type was normalized by the frequency of earthquakes within each California county.  

Conclusions

Areas of high risk are centered on highly populated counties in Southern California.  Hispanic individuals are more affected than those below poverty level do to a larger overall population.  Earthquake risk decreases from 2000 to 2010 in both population categories due to a decrease in earthquakes occurrences in 2010.   For Hispanic individuals, the areas of highest risk shift southwards.  All four maps highlight Los Angles as the county most at risk during both Census years. This high risk level is associated with the county’s proximity to the San Andres fault, high population density, and predominately urban makeup.

Map Links

ESRI Story Map: http://www.arcgis.com/apps/StorytellingSwipe/index.html?appid=106aac6b00354096ac82dcc15425fbed&webmap=af4b0df0e94b46bead1d881c436b746b