Earthquake Risk Mapping for the Continental United States:
Carrissa Beasely’s geospatial project report, May 2011
Earthquake occurrences are known to be very unpredictable. The government agencies have been collecting the actual earthquake records for sometime in the United States and make the earthquake database publicly available (USGS).
This research project compiled the data from 1960 through 2000, averaged for earthquakes of moderate to severe magnitudes (5 to 9 on Richter’s scale), and analyzed for each decade for risk mapping. A spatial risk map of earthquake was prepared that shows the continental United States in eight zones (Zone 1 with the lowest risk to Zone 8 with the highest risk of large earthquake occurrence). The earthquake risk zone map was prepared using the GeoMediaProsoftware.
The spatial map reveals that Zone 8 (which includes the San Andreas fault) is the zone with the highest average earthquake magnitude, while Zone 6 (including the New Madrid seismic zone of southeast Missouri and northern Mississippi) is the third highest. The table shows the unadjusted earthquake magnitude averages for each zone and the population affected by area (population density). Both Zones 6 and 8 have high population densities with many large cities making them vulnerable to earthquake damage risk. Zone 6 is more unpredictable than its predecessor zones.
According to the USGS: “the New Madrid seismic zone of southeast Missouri and adjacent States is the most seismically active in North America east of the Rockies. During the winter of 1811-1812 three very large earthquakes devastated the area and were felt throughout most of the Nation. They occurred a few weeks apart on December 16, January 23, and February 7. Hundreds of aftershocks, some severely damaging by themselves, continued for years. Prehistoric earthquakes similar in size to those of 1811-1812 occurred in the middle 1400’s and around 900 A.D. Strong, damaging earthquakes struck the southwestern end of the seismic zone near Marked Tree, Arkansas in 1843 (magnitude 6.3), and the northeastern end near Charleston, Missouri in 1895 (magnitude 6.6). Since 1900, moderately damaging earthquakes have struck the seismic zone every few decades. About twice a year people feel still smaller earthquakes that do not cause damage.”
Dr. Uddin’s note: If the historical trend repeats in Zone 6 then the next big one is expected in the 21st century. This zone includes Memphis and Northern Mississippi region.
The following Google Map shows USGS real-time earthquake monitoring globally.