No Active Fault Problems in Louisiana?

Ghulam Sarwar and Reid Bohlinger
Louisiana Department of Natural Resources, Baton Rouge, Louisiana

Although Louisiana is located near such tectonically active areas as the New Madrid fault zone and the Texas-Mexican-Gulf of Mexico-Caribbean domain, the state experiences only mild seismicity. However, the area is not free of active faults. A few active faults are known. Examples are the Baton Rouge and the Toledo Bend reservoir area faults. However, the seismicity and published surface and subsurface data show that the basement is active. Also, there are numerous shallow faults that can be projected up to the surface. This suggests that there are many more active faults at the surface than we know about.

Swampy conditions, stream cover, and human activity all make surface faults difficult to locate. Lineaments, both northeast and southwest are common, but so far have kept their secrets. Geomorphic features on satellite and aerial photographs, and on the ground can be helpful. Geomorphic examples include pattern of stream channel meanders and grade changes, suspicious stream channel offsets, sharp changes in the direction of flow, scarps, ramps, linear ridges, vegetation changes, chronic road sags, and sink holes that keep swallowing tar and dirt over decades. Cracking walls and foundations of buildings, crooked bridges, wavy rail road tracks, and even a hot spring may be suspicious. Several of these features have been noticed near Monroe, Lake Charles, the Red River, Shreveport, and elsewhere.

We must incorporate the basement in the study of active faults and integrate all sorts of data to study subsurface faults that relate to surface faults. This enables us to better understand the risks involved for all of us.

AAPG Search and Discovery Article #90080©2005 GCAGS 55th Annual Convention, New Orleans, Louisiana