A methodology that combines high-resolution topographic mapping, field observations, subsurface evaluation, and geodetic data analysis has successfully located several fault-related geomorphic steps in an area of southwestern Louisiana once thought to be relatively devoid of such features. Comparison of height differences of benchmarks straddling these suspected fault-related steps shows that vertical displacement rates on faults in the study area ranged from about 2 mm/yr to as much as 6 mm/yr during the 1960s and 1970s. However, leveling data obtained as recently as January 2005 reveals that the majority of these faults are currently moving at rates of less than 1 mm/yr.
This study identifies the presence of several previously mapped fault-related steps as well as some unidentified geomorphic features with the use of LIDAR (Light Detection and Ranging) digital elevation models and aerial photography. The majority of these topographic steps correlate well with upward projections of known subsurface faults, which suggests that they are of tectonic origin. Also, field observations have located offsets of roadways and damage to built structures due to the differential motion caused by active faulting. These lines of evidence, combined with the leveling data, suggest that the geomorphic features in the study area are the surface expressions of active faults that have moved during the past half-century. A possible cause for the accelerated fault slip rates computed for the 1960's and 1970's could be the substantial lowering of the piezometric surface that occurred due to increased subsurface fluid withdrawal. This suggests that in addition to the natural causes of faulting, anthropogenic activities may have also affected fault motion in this area of Louisiana.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-07122005-165749 |
| Date | 14 July 2005 |
| Creators | Heltz, Jordan Oliver |
| Contributors | Roy K. Dokka, Frank Tsai, David Constant |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-07122005-165749/ |
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