New Madrid Fault System, image courtesy UM-CERI
With all of the recent earthquake activity across the globe, I thought it would be a good time to review the earthquake threat that the Mid-South faces on a daily basis. Though not specifically weather-related, earthquakes fall into a broader "geography" or "earth sciences" category, of which meteorology is also a part. Therefore, it is appropriate to address here.
In the past 7 days, there have been 49 earthquakes of magnitude 5.0 or higher across the globe. A world map view shows that many are centered around the well-known and very active Pacific Rim. While this may be something akin to "normal," what has caught my attention are the number of magnitude 6.0 or higher earthquakes. On the 10th, a magnitude 6.5 occurred just off the northern California coast. And we all know about the 7.0 that struck Haiti on Jan. 12. That was followed by fourteen aftershocks of magnitude 5.0 or higher - all less than 24 hours after the initial quake - and dozens of smaller ones. One the 14th, a 6.0 rumbled southwest of Guam in the western Pacific. While this region is frequented by tremors, a 6.0 is still pretty strong even for the Pacific. On the 18th, another strong 6.3 quake occurred in the Drake Passage (between South America and Antarctica, south of Argentina). Finally, this morning, another 6.0 struck near the Guatemala/El Salvador coast. (All information above courtesy USGS.gov.)
We should be reminded that we live very near the New Madrid Fault System, which produced one of the strongest earthquakes in U.S. history 199 years ago (1811) and has the greatest earthquake risk east of the Rockies. A Fact Sheet published by the USGS details the continuing threat that this fault poses. In addition, an urban seismic hazard mapping report for Memphis was published by USGS in 2006 which may be of interest.
I would invite you to use this opportunity for education - know what you need to do to be prepared should an earthquake strike and what to do during and after a quake. The Fact Sheet quoted above indicates that the region could see landslides along the river bluffs, "ground failures [...] including soil liquefaction along the Mississippi River floodplain," impassable roadways due to bridge collapse or fissures in the road surface, disruption of agriculture and farmland flooding that could contaminate water sources, and failure of levees and riverbanks. With it's aging infrastructure, Memphis is "particularly vulnerable when subjected to severe ground shaking," including the possibility of building failure due to their being built prior to the writing of code that require seismic resistance.
None of this is meant to cause fear or worry, but instead to serve as a reminder that education and preparedness are key. Who knows when "the big one" may strike, but there is no indication that sometime in the future it won't.
For more information, visit these links:
United States Geological Survey Earthquakes Homepage
Earthquake Preparation - Before, During, and After an Earthquake (FEMA)
USGS Earthquake Notification Service
USGS Earthquake Info for Kids
University of Memphis Center for Earthquake Research and Information (CERI)
CERI's New Madrid Fault System page
Central U.S. Earthquake Consortium
ABC/Good Morning America Story (Jan. 18. 2010) on the central U.S. earthquake risk
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