Sunday, November 06, 2011

Oklahoma Earthquake

A magnitude 5.6! Like, WTF? Oklahoma?

John in Oklahoma City writes about his experiences. (And by the way, Sacramento is one of the least-seismically-active parts of California, and my experience with quakes is quite minimal by comparison):
Hey Marc,
I know this is of little interest to a Californian who is accustomed to such things but we had two earthquakes here yesterday. The first one occurred about 2:15 AM Saturday morning and, at magnitude 4.7, was felt over a fairly large area. I awoke to the sound of the bedroom door rattling. I thought perhaps that our cats were engaging in some late night wildness so when the noise stopped after about 10 seconds I went back to sleep. The second quake occurred at about 10:50 PM Saturday night and was much more dramatic. I was sitting in an easy chair when I heard a strange rumbling. After a few seconds I said to Linda, "Is that another earthquake?" The rumbling--much like the ground noises from a passing train but without the rhythmic clicking of the wheels--continued for about 20 seconds when my son, Peter, came into the room and said, "Earthquake!" At about that point the rumbling increased in intensity and the house began to creak and groan a bit. The more intense rumbling lasted about 20 seconds before it began to abate. The entire event lasted just under one minute. The magnitude of that quake was 5.6 which made it the largest quake recorded since statehood in Oklahoma. The epicenter was approximately 50 miles east of here on a fault that has been historically inactive. Both quakes yesterday appear to have been on the same fault but were separated by about 10 miles. I have been in Oklahoma just over 30 years now and for most of that time there was almost no seismic activity. During the last three years the region east of Oklahoma City has become quite active with more than 1000 measureable seismic events having occurred there so far this year (the norm for the last few decades has been around 50). In any case, after 55 years, I am happy to have experienced an earthquake.

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