ABSTRACT

A survey of the historical seismicity of Texas has revealed 100 earthquakes of magnitude 3 or greater in the Lone Star State from February 1847 to December 1984. The largest earthquake of mb = 5.9 occurred on August 16, 1931 near the town of Valentine in west Texas. This event damaged many buildings, and the total felt area exceeded one million square kilometers (400,000 square miles). Earthquakes in the Valentine area as well as other events farther west near El Paso are probably related with the Rio Grande rift system. Several large events in the Texas Panhandle occur along a zone of crustal weakness that follows the trend of the Amarillo uplift. Earthquakes in eastern Texas are associated with several fault systems in the Gulf Coastal Plain. A large earthquake on October 22, 1882 had previously been located in northeast Texas near the town of Paris; however, a reevaluation of the intensities suggests the epicenter was probably farther north in Oklahoma. Several other events in previous catalogs have been discarded or relocated.

Some of the more recent Texas earthquakes may have been induced by oil field operations. Seismic activity in west Texas near the towns of Kermit and Snyder are probably caused by waterflooding projects. Several recent earthquakes in the Gulf Coastal Plain may be associated with fluid withdrawal from oil and gas fields in normal faults.