Largest Earthquakes in Oklahoma
The only known surface expression of an active fault occurs in southwestern Oklahoma. The last slip on this fault is estimated to be about 1300 years ago and may have been equivalent to a magnitude 6.5 or 7.0 earthquake. This fault is known as the Meers Fault and is visible from the air as can be seen in the following picture.
The OGS located 1047 earthquakes in Oklahoma in 2010. 103 of these earthquakes were reported felt. The largest earthquake to occur in 2010 was the October 13 magnitude 4.7 earthquake which occurred near Norman, Oklahoma. This earthquake was felt from Kansas City to south of Dallas, Texas. The was also a magnitude 4.1 which occurred on February 27 in Lincoln County near Prague, which was felt through parts of Oklahoma and Kansas.
Oklahoma County continued to have a significant amount of earthquake activity associated with the Jones swarm. The OGS located 695 earthquakes in Oklahoma County in 2010, and of these 65 were reported felt. The largest earthquake to occur in the swarm was a magnitude 4.0 earthquake. The OGS deployed additional seismic instrumentation to the area in early 2010. This instrumentation has allowed us to determine a great deal about the earthquakes occurring in Oklahoma County. We have not discovered a cause for the dramatic numbers of earthquakes, but continue to examine the data.
Are all these earthquakes unusual?
Yes the number of earthquakes felt in 2009 and 2010 are unusual. The frequency of earthquakes has temporarily increased in Oklahoma, these earthquakes do not appear to be inconsistent with what might be called normal seismicity for Oklahoma.
Why do Oklahoma earthquakes sound like explosions, thunder, etc?
Explanation by James Lawson
Earthquakes produce two types of seismic waves through the earth. P waves move the eatrh's surface mainly up and down, and S waves move it mainly side to side. The P waves travel faster so they arrive first.
As the P waves arrive at your location, they cause the ground surface around you, and your floor, to vibrate up and down, just like a loudspeaker cone. The movement is too tiny to be seen, but just large enough to cause a low frequency sound. These sounds are often described as a boom or rumble. To persons who expierenced the Oklahoma City bombing, the earthquake sounds are similar to the air blast sounds from that atrocity. Many check to see if their furnace exploded, or go outside to look for an explosion. The sounds are frequently described as "like a sonic boom, only somehow different".
Persons near an Oklahoma earthquake epicenter may hear and/or feel the P wave, and shortly after (only a second or so) may feel and/or hear the S wave. So you may have any of the following:
1. sound only
2. vibration only
3. sound and vibration
4. sound followed by vibration
5. vibration followed by sound
6. sound and vibration followed by vibration
or any other possible combination. 1., 2., 3., and 4. are the most common.
There have been a number of instances (especially in Europe) in which vibration and/or sound from relatively small earthquakes, have precipitated heart attacks. Some of these attacks have been fatal. Particularly in recent times when car and truck bombs have become relatively frequent, an unexpected boom and/or shake may cause sudden fear, which may threaten the lives of persons with known or unknown heart conditions. This is the greatest danger in most small felt earthquakes.
When something goes boom in the night, try not to be startled. It may only be a small earthquake. Even if it is an explosion, it is over by the time you hear it.
If you have a question of your own about earthquakes in Oklahoma please use the link below to submit your question.