Avian Flu Diary: Sometimes, Where You Least Expect It . . .

# 6235

Although little remembered today, on November 18th, 1929 a 7.2 magnitude earthquake struck offshore from Newfoundland, in the Grand Banks. Three hours later a 3 to 4 meter tsunami washed across many coastal fishing villages on the Burin Peninsula, killing 28 people and leaving as many as 10,000 homeless.

Somewhat better known is the 1886 (Est. 7+ magnitude)quake that struck and devastated much of Charleston, South Carolina. Shaking was felt as far north as Boston, south to Cuba, and west as far as New Orleans.

And just last year, sections of Virginia and Washington, D.C. were rattled by a `surprise’ 5.8 earthquake centered in Mineral, Virginia (see USGS Statement On The Virginia Earthquake).

All three quakes share a common element; they did not occur on a traditional earthquake fault line (a continental plate boundary).

Instead they were intraplate earthquakes that occurred on passive passive margins, a type of fault that is little studied and poorly understood, but that can be found in many places around the world, including the eastern seaboard of the United States.

Below you’ll find an earthquake hazard map from FEMA’s website covering the central and eastern United States.

The colors in the map reflect “seismic design categories” (SDCs), which anticipates the likely intensity of seismic shaking in a region.

As you can see, the New Madrid region in Missouri, Tennessee, and Arkansas is considered at highest risk, but the coastal region of South Carolina is also at risk from strong earthquakes.

While people living in California, Alaska, Hawaii, and the Pacific Northwest may be somewhat prepared for earthquakes, the same is unlikely to be said for folks living in Boston, New York City, and Montreal, Canada.

We’ve an analysis of the 2011 Virginia quake that appeared recently the AGU’s journal Geophysical Research Letters that warns of the dangers of these poorly understood fault lines.

doi:10.1029/2011GL050310

Mineral, Virginia, earthquake illustrates seismicity of a passive-aggressive margin

Key Points

Passive continental margins sometimes have large earthquakes

They pose hazards due to both tsunamis and shaking

Progress on these issues requires integrating seismic, geodetic, and geological

Note: You’ll find a global map showing known `passive’ fault lines in the above paper.

While a 6.0 earthquake might do only minor damage in an earthquake prone area like California, where building codes take ground shaking into account - in cities where quakes are less common - the damage could be extensive.

All of which means you don’t have to live on a major fault line in order to be at seismic risk, and even those who live along the eastern seaboard ought to be earthquake aware.

Boston’s Museum of Science has a short video on Earthquake potential and preparedness in New England, which you may view by clicking HERE or the image below (will take you to their site).

Although earthquake preparedness guides tailored for these passive fault regions are often hard to come by, you can avail yourself of the many toolkits and preparedness materials produced for California, the Pacific Northwest, and the New Madrid region.

Last September, during National Preparedness Month, I wrote about some of the guides available to help you prepare. You can revisit that blog at:

NPM11: Are You Earthquake Prepared?

While earthquake threats should not be foremost in the minds of people living away from regular fault lines, few places in the US are completely immune.

It therefore make sense to prepare for `all threats’, so that no matter what disaster occurs, you will be ready.

And to become better prepared as an individual, family, business owner, or community to deal with all types of disasters, I would invite you to visit the following preparedness sites.