--> Abstract: Segmentation of Normal Faults in the Dip Direction and its Significance in Fault Seal Analyses, by Amgad I. Younes and Atilla Aydin; #90914(2000)
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AMGAD I. Younes1, Atilla Aydin2
(1) Stanford University, Stanford, CA
(2) Stanford University

Abstract: Segmentation of normal faults in the dip direction and its significance in Previous HitfaultNext Hit seal analyses

Previous HitFaultNext Hit segmentation along strike is commonly observed in outcrop but segmentation along dip direction is difficult to observe in the field and to resolve in seismic. We argue that sense of Previous HitfaultNext Hit segmentation has considerable implications for Previous HitfaultNext Hit rock formation and should be carefully considered in any Previous HitfaultNext Hit seal analysis.

Along-dip segmented faults form echelon arrays consistently stepping perpendicular to Previous HitfaultNext Hit strike, towards either the hanging wall or the footwall. Faults step at contacts of competent and incompetent layers. Continued slip on Previous HitfaultNext Hit segments produces a coalesced single Previous HitfaultNext Hit strand. During Previous HitfaultNext Hit coalescence, the deformation within the steps produces two distinct Previous HitfaultNext Hit rock types depending on the sense of steps. In the hanging wall steps, deformation is dominated by shale smearing which involves the rotation of the incompetent layers until they are smeared parallel to the Previous HitfaultNext Hit (smearing). In contrast, deformation along footwall steps forces the shale out of the step (extrusion), and eventually becomes dominated by brecciation of the brittle hanging and footwall rocks. In addition, our data shows that the thicker incompetent layers cause larger steps, predominantly, for hanging wall steps. Therefore, the dip angle of coalesced Previous HitfaultNext Hit segments may become shallower (for hanging wall steps) or steeper (for footwall steps) depending on the ratio of competent to incompetent layers. Subsurface examples from the Gulf of Mexico will be discussed.

The hydraulic properties and sealing capacity of a Previous HitfaultNext Hit may then depend on the Previous HitfaultNext Hit step type and associated Previous HitfaultTop rock material; smeared shale or breccia.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana