Created/edited: 4/09/2008
Reviewed/approved: 5/8/2007

Earthquakes and Volcanoes:


The following data is taken from the University of Texas web site at

An earthquake is a motion or trembling that occurs when there is a sudden breaking or shifting of rock material beneath the earth's surface. This breaking or shifting produces elastic waves which travel at the speed of sound in rock. These waves may be felt or produce damage far away from the epicenter-the point on the earth's surface above where the breaking or shifting actually occurred.

Earthquakes do occur in Texas.  Within the twentieth century there have been more than 100 earthquakes large enough to be felt; their epicenters occur in 40 of Texas's 257 counties. Four of these earthquakes have had magnitudes between 5 and 6, making them large enough to be felt over a wide area and produce significant damage near their epicenters.

In four regions within Texas there have been historical earthquakes which indicate potential earthquake hazard.  Two regions, near El Paso and in the Panhandle, should expect earthquakes with magnitudes of about 5.5-6.0 to occur every 50-100 years, and even larger earthquakes are possible. In northeastern Texas the greatest hazard is from very large earthquakes (magnitude 7 or above) which might occur outside of Texas, particularly in Oklahoma or Missouri-Tennessee. In south-central Texas the hazard is generally low, but residents should be aware that small earthquakes can occur there, including some which are triggered by oil or gas production. Elsewhere in Texas, earthquakes are exceedingly rare. However, the hazard level is not zero anywhere in Texas; small earthquakes are possible almost anywhere, and all regions face possible ill effects from very large, distant earthquakes.

Volcanoes in Texas have been practically non-existent.  The only real threat from a volcano for San Antonio is in the event that a super volcano such as the caldera under Yellowstone National Park should erupt with a cataclysmic eruption.  Such events only occur about every 100,000 years so if there were an eruption of the Yellowstone caldera scientist state there is little if anything that anyone from Montana to Texas could do to protect themselves.


If there is a natural disaster during the normal work day, the senior member of the Crisis Management Team available on site at the time will decide whether or not to evacuate the building, send the staff home, and cancel classes or to seek shelter in-place.


If there is natural disaster after normal work hours, the senior member of the Crisis Management Team available on site at the time of the disaster or the Security Guard will decide whether or not to evacuate the building and cancel classes or have everyone seek shelter in-place for safety.  In the absence of the Security Guard any instructor on site can make that determination.


Locations of earthquakes and earthquake sequences that have occurred in Texas or that were felt by Texas residents. The numbers are the year of occurrence.

Locations of earthquakes felt in Texas



 Earthquake faults and seismically active areas of the state:



Earthquake probability:




Close window