Another small earthquake struck near the border separating Alabama and Florida, according to reports.
On March 6, the first earthquake struck the area. Another hit on March 11, and two more hit on March 13, it was reported.
Alabama’s Geological Investigations Program told the NBC affiliate that the five earthquakes are part of the “normal seismic activity” in the region.
Quakes East of Rockies Felt More Intensely Than the West
While most of North America east of the Rocky Mountains has infrequent earthquakes, there are hotspots of intense quake activity.The USGS points out that while earthquakes east of the Rockies are less common than in the West, they are typically felt over a much broader region.
“East of the Rockies, an earthquake can be felt over an area more than ten times larger than a similar magnitude earthquake on the west coast,” the USGS says.
“It would not be unusual for a magnitude 4.0 earthquake in eastern or central North America to be felt by a significant percentage of the population in many communities more than 60 miles from its source. A magnitude 5.5 earthquake in eastern or central North America might be felt by much of the population out to more than 300 miles from its source.”
Concerned?
The USGS says an earthquake of a 6.0 on the Richter scale hit about 50 miles northeast of Boston in 1755, leaving the city “heavily damaged.”“Other strong earthquakes recorded in the continental US were centered in southeastern Missouri near the border with Arkansas, Kentucky, and Tennessee. In the winter of 1811-1812, a series of three powerful earthquakes of magnitudes about 7.0 to 7.8 and hundreds of aftershocks occurred near New Madrid, Missouri,” according to the agency.
Some of these quakes, the USGS said, caused the land to turn into “rolling waves.”
What’s more, they changed the course of the Mississippi River and were felt 800 to 1,000 miles away.
“Eastern North America has older rocks, some of which formed hundreds of millions of years before those in the West,” the agency wrote. “These older formations have been exposed to extreme pressures and temperatures, making them harder and often denser.”
“Faults in these older rocks have also had more time to heal, which allows seismic waves to cross them more effectively when an earthquake occurs. In contrast, rocks in the West are younger and broken up by faults that are often younger and have had less time to heal. So when an earthquake occurs, more of the seismic wave energy is absorbed by the faults and the energy doesn’t spread as efficiently.”