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Abstract: Geometry, Spatial Distribution and Scaling Relationships of Faults in Oblique Rift Zones

CLIFTON, AMY E., Rutgers University, Dept. of Geological Sciences, Piscataway, NJ

Analysis of photos of scaled clay models revealed significant changes in the evolution of fault populations as the acute angle (alpha) between the rift axis and the spreading vector varies. Sub-populations of fractures develop during oblique rifting, each of which exhibits unique characteristics which must be examined separately from the total population. Subpopulations interact during growth, linking to form complex, zigzag faults with average strikes oblique to both the rift trend and spreading vector. The interconnectedness of faults affects the partitioning of strain and the scaling of segment linkage during fault population evolution. Detailed mapping of active, en echelon faults on the Reykjanes Peninsula of Iceland (alpha = 28 degrees) revealed two sub-populations of faults that interact in the relay ramp, adding volume to the rock. This winter I made new scaled models, the analysis of which will focus on the interaction of sub-populations during linkage, as well as further quantifying fault scaling and spatial distribution. Additional field work in Iceland is necessary to check the usefulness of the models. The Reykjanes fissure swarm is comprised of an evolving population of faults and fissures which cut through lava flows with well constrained ages. Fractures at many different stages of growth will be mapped in detail, enabling the identification of segment boundaries and the damage zones associated with segment linkage.

A better understanding of fault population evolution is an expected outcome of this study. Fault intersections localize the geothermal systems that power much of Iceland. Of particular interest to the oil industry is the ability to predict the location of damage zones associated with fault growth and linkage which increase the bulk volume and porosity of rock.

AAPG Search and Discovery Article #90931©1998 AAPG Foundation Grants-in-Aid