FAQ

FAQ - Frequently Asked Questions

If you have a question of your own about earthquakes in Oklahoma please use the link below to submit your question.

Ask a seismologist

 


Are all these earthquakes unusual?

Yes the number of earthquakes felt in 2009, 2010, 2011, 2012, 2013 and currently in 2014 are unusual.  The frequency of earthquakes has increased in Oklahoma however, the majority of these earthquakes align with the natural stresses in Oklahoma and appear to be occurring on previously known and unknown faults, therefore, these earthquakes do not appear to be inconsistent with what might be called normal seismicity for Oklahoma.

Is there any data about historical seismic activity in Oklahoma below that of a 3.0? Growing up I always heard that Oklahoma had more earthquakes than another state, but they were so small you couldn't feel them.  However, I can't find any data to support that. All the press I've been reading has been talking about (and showing charts) of the large increase of earthquakes but they are only showing events that are 3.0 and above. I wonder if we are having more earthquakes of any intensity overall or if its just that many of the earthquakes that we are having are stronger than they have been in the past.

Oklahoma has a recorded seismic history dating back to 1882. However, the OGS has only been operating a seismic network since 1978. Ultimately, we are having more earthquakes of all intensities.


Can individuals get a device that measures earth tremors on their property?

Send us an email expressing your interest in housing an OGS temporary or permanent seismic station to the ‘Ask a Seismologist’ link at the top or bottom of this page. We will keep your information on file and contact you when and if we have the equipment and interest in placing one on your property.

Another option is to look into the Quake-Catcher-Network

http://qcn.stanford.edu

QCN is a volunteer hosted real-time strong-motion seismic network utilizing sensors in and attached to internet-connected computers. 

Is it better to have a large quantity of smaller earthquakes like we have been having? Does that act as some sort of pressure relief instead of the force building and building till we have the "big one"? It would seem that a series of small slippages would be better than one large one.

The increase of magnitude of 3.0 and greater earthquakes indicates a greater possibility of having a magnitude 4.0 or greater event in the future. This arises from the Gutenberg-Richter law which expresses the relationship between magnitude and frequency of earthquakes in a given region and time period. Simply stated, for every 10 magnitude 2.0 earthquakes we have we can expect a magnitude 3.0 earthquake. So, for every 100 magnitude 2.0 earthquakes we have we can expect 10 magnitude 3.0 earthquakes and one magnitude 4.0 earthquake. This relationship holds worldwide and does not vary significantly from region to region or over time.

Furthermore the energy released by a small event (M2.0) is nowhere near comparable to the energy released by a larger event (M5.0). Each whole number step in the magnitude scale corresponds to the release of about 31.6 times more energy than the amount associated with the preceding whole number value. For instance, a magnitude 2.0 earthquake releases 31.6 times more energy than a magnitude 1.0 earthquake, while a magnitude 3.0 earthquake releases about 1000 times (31.6x31.6) more energy than a magnitude 1.0 and a magnitude 5.0 earthquake releases 1,000,000 times (31.6x31.6x31.6x31.6) more energy than a magnitude 1.0. 

Why does the USGS and Leonard Geophysical Observatory differ on magnitudes of earthquakes here in OK. Example 4/20 USGS has one of the quakes at 4.0 and OGS has it at 3.7..... I would like to know why the numbers are different.

We estimate magnitude based off of ground motion recordings at different sites.  So the OGS only uses stations within or near Oklahoma and the USGS can use stations over a much larger area to calculate magnitude.  In addition there are many different ways to calculate magnitude and each make different assumptions and provide different results.  There is no single magnitude for any earthquake there are always multiple estimates, but they generally agree quite well.  Magnitude can be expected to have an uncertainty of +/- 0.2 magnitude units roughly. 

Why do only a few of the Oklahoma earthquakes show up on the USGS site?

The USGS, generally, only reports Oklahoma earthquakes larger than magnitude 2.5.

I felt an earthquake last night but can't find any report… Do you all report small events?

With the rate of seismicity currently occurring in the state of Oklahoma and our limited resources we are unable to locate all earthquakes. At a minimum we are working hard to locate all events above a magnitude 2.5 and you very well may be experiencing smaller events that are not getting located at this time. We will be going back through our catalogs and locating these smaller events in the near future.

How frequently does the OGS earthquake list get updated?  It seems at times that there is a several hour delay.

Our Preliminary Earthquake Information list gets updated as earthquakes are located if there is a delay it is either because we do not have an analyst working (during evenings or weekends) or there is a lull in seismic activity. 

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 earth'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 experienced 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.

Ask a seismologist