Carl E. Norman1
(1) University of Houston, Houston, TX
Abstract: Kinematic behavior of aseismic active faults in the Texas Gulf Coast
Kinematic data gathered over a period of 14 years are now available for 30 active faults in the western Gulf Coast region within a 40-mile radius of downtown Houston, Texas. All are listric normal faults. Some extend regionally for several miles, while others occur locally in radial patterns around salt diapirs. Episodic movement occurs at average annual rates of up to 3 cm per year.
The data are in the form of elevation changes recorded from bench marks spaces up to 25 feet in lines 150 to 200 feet long across the strike of the faults. Close spacing of bench marks allows determination of the width of the zone of disturbed ground across the fault and characterization of deformation patterns in the fault zone.
Both kinematic and geometric data show that rates of fault movement decrease progressively from the center to the ends of a fault where it passes laterally into a monoclinal flexure, which in turn dies out rapidly. Individual movement events are in the millimeter to sub-millimeter range, except that events in the centimeter range correlate with distant strong earthquakes. Movement rates over geologic time are also variable, as recognized from plots of fault throw against depth for single faults
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana