Earthquakes Around the Globe
Except for the strength of some of them, the latest earthquakes are not unusual, and the tremors are not related, according to SMS associate geology professor Stan Fagerlin.
(voice of Stan, describing plate movements, etc.)
The recent quakes include two in Alaska last Sunday, Nov. 3 ... a magnitude 4.0 in the morning, and a big one measuring 7.9 in the afternoon. That quake was felt as far away as Louisiana.
Also Sunday: a magnitude 4.3 earthquake shook Nebraska. A 4.5 earthquake killed 10 people in northern Pakistan, and a magnitude 6.1 hit northern Japan.
On Monday, Nov. 4, southwestern Japan was rocked by a magnitude 5.7 earthquake, and last Saturday, Oct. 26, a quake measuring 7.7 on the Richter scale killed two people on Indonesia's Sumatra Island.
These quakes followed one in central Italy last week that toppled a school and killed 29 people.
Stan Fagerlin says using the Richter scale, the power of an earthquake is increased 10 times from one whole number to the next. For instance, amplitude of the ground shaking increases tenfold from a 6.0 to a 7.0 quake.
But there's more to the equation.
(voice of Stan, noting that the energy of an earthquake is doubled with every two-tenths of a point increase in magnitude.)
Fagerlin says the earth's rigid outer surface is broken into a series of blocks, or what scientists call plates, and earthquakes occur when these plates move relative to one another.
(voice of Stan, talking about tectonic plates. He says powerful, side-to-side plate movement occurs in, among other places, the San Andreas fault in southern California and the Midwest's New Madrid fault in southeast Missouri.)
In fact, some of the most powerful earthquakes to hit the lower 48 states occurred along the New Madrid Fault in southeast Missouri in 1811-12. Scientists can only estimate, of course, but those earthquakes are thought to have measured well over 8.0 on the Richter scale.
Stan Fagerlin says the cycle of the big New Madrid quakes is everycouple of hundred years or so, and they are overdue. He also says less powerful, but still very strong earthquakes along the New Madrid are overdue in their cycle of occurrence.
(voice of Stan, discussing a 6.0 magnitude quake along the New Madrid. There's hasn't been one since 1895, and by some estimates they should happen every 75 years or so.)
Fagerlin believes a 6.0 earthquake on the New Madrid would cause very little damage in the Ozarks, but if an 8.0 magnitude quake were to occur ...
(voice of Stan: "Certainly our attention would be grabbed." He describes racked plaster in homes and suspects a lot of suspended ceiling foam tiles would come down. He also cites the potential for injuries.)
Outcue: Stan Fagerlin is an associate professor of geology at Southwest Missouri State University. Reporting for KSMU News, I'm Mike Smith.