Monday, March 8, 2010

Why are we having so many earthquakes?

Another earthquake – this time in Turkey. Earthquakes are certainly in the news. Fortunately, earthquakes are not a frequent occurrence in Virginia, but they do happen. Do you remember the one on December 9, 2003? It measured 4.5 on the Richter scale; its epicenter was just south of the James River in Powhatan County. I remember it well; it was quite an experience!
With all the recent reported earthquakes, you might wonder if they are related; that is, could the earthquake in Haiti cause the one in Chile, which might then cause the one in Turkey and so on? Here are some frequently-asked earthquake questions and their “myth-busting” answers:
1. Why are we having so many earthquakes?
Although it may seem like it, we are not having more earthquakes than usual. Earthquakes do occur in clusters, though, but clusters are predicted by statistics and do not mean the quakes are related. (Also, there are long periods when earthquakes are not in the news, but that is not considered unusual.) Several factors make it appear earthquake frequency has increased:
(a) Better reporting – in 1931 there were 350 stations reporting earthquakes; now there are 4000. Current stations locate an average of 50 quakes per day. In general, there are about 18 major quakes per year (7.0-7.9) and one great one (8.0+).
(b) Increasing global population makes for more casualties and thus more reporting.
(c) Better communication around the globe allows us to know about earthquakes quickly so it’s timely and newsworthy.
2. Can scientists predict earthquakes?
Unfortunately, they do not know how. However, using scientific data, they can calculate the probability one will strike in the future.
3. Can animals predict earthquakes?
From the days of ancient Greece, there have been reports of animals behaving strangely just before an earthquake. Scientists have investigated and cannot find consistent and reliable animal behavior prior to an earthquake.
4. Is there a particular time of day that earthquakes tend to occur? Do they occur more often at certain time of the month or year?
Earthquakes are equally probable at all times of the day, month or year.
5. Can the ground open up during an earthquake?
In an earthquake, the earth moves along a fault not perpendicular to it, so the ground would not open up. If it did, there would be no friction, thus no quake. Landslides and other ground failures caused by earthquakes can cause crevasses and depressions to form, however.
6. Will California eventually fall into the ocean?
No. The Pacific Plate runs into the North American Plate at the San Andreas Fault. The Pacific Plate is moving northwest relative to the North American Plate at a rate of 46 mm/year (about the rate your fingernails grow). California will not fall into the ocean, but LA may one day have a very cold climate – it is heading toward Alaska.
The above information came from the US Geological Survey. Want to know more? Go to


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