April 8, 2010 in Washington Voices

Some wonder whether earthquakes have a season

Randy Mann
 

With all of the recent earthquakes, many of my physical geography students are asking, “are we seeing more seismic activity than usual?”

Many scientists claim that the recent activity is within the normal realm. No one is certain whether the increased number of earthquakes is a prelude to more shakers, or it could be just chance.

The strongest U.S. earthquake recorded happened on Good Friday, March 28, 1964, at Prince William Sound in Alaska. It was measured at an incredible 9.2 magnitude and devastated the city of Anchorage.

The largest ever-recorded quake in the world happened in Chile. It wasn’t the recent shock earlier this year, but the one on May 22, 1965. The epicenter was offshore and measured 9.5 magnitude. The earthquake in Chile on Feb. 27 was a magnitutde 8.8.

The most famous quake was the powerful magnitude 7.8 (some estimate more than magnitude 8) of April 18, 1906, in San Francisco. That quake killed more than 3,000 people and injured 10,000. Damage totals exceeded $1 billion, mainly from fires from Santa Rosa southward to San Jose. That would be more than $50 billion in today’s currency.

Many people have wondered if there is a connection between the weather and earthquakes. Geologists maintain that there is no relationship as seismic activity is the result of geologic processes within Earth and can happen in any weather and any time during the year.

However, some wonder why approximately 65 percent of the most notable earthquakes nationwide were occurring in the spring and fall seasons and only about 35 percent in the winter and summer periods. In other words, are there “earthquake seasons,” much like hurricane, snow and tornado seasons? Maybe yes, maybe no.

In our region, the largest quake occurred in 1942 and was centered 35 miles northeast of Spokane. It was a 5.5 magnitude. In 2001, Spokane was in the throes of an “earthquake swarm.” Nearly 100 earthquakes were recorded over a six-month period with a 3.7 magnitude reported on June 25, 2001. Scientists are still uncertain why our region experienced this swarm of quakes.

As far as our weather is concerned, the cool and wetter-than-normal spring should continue into at least early May. As I write this column early Tuesday, the snow was flying and don’t be surprised to see more snow over the next few weeks. Although the overall spring season is expected to be a bit cooler and wetter, I do expect to see many sunny days with pleasant afternoon temperatures. The summer still looks dry and hot.

Contact Randy Mann at randy@longrange weather.com.


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