Quantitative Analysis of Controls from Relay Ramp Parameters and Evolution

Huenink, Christina ¹; Trudgill, Bruce ^1
1 Geology and Geological Engineering, Colorado School of Mines, Golden, CO.

Relay ramps are ephemeral structures that form during the development of normal fault systems. As two offset normal faults propagate toward one another and overlap, an inclined relay ramp zone accommodates further deformation until strain exceeds the strength of the relay zone and breaching occurs. Relay ramps form at many different scales, their sizes ranging from centimeters to over a hundred kilometers.

The nature of the controls on relay ramp development has often been discussed in a general sense, e.g., preexisting structures, lithological variations, ramp width, fault overlap lengths, etc. However, a better understanding of the variables that control ramp development and breaching is needed before any quantitative predictions can be made as to whether or when a ramp in the subsurface is/was breached.

Relay ramps can be differentiated into four categories based on their size and structural setting: (1) crustal scale, (2) detached/mobile substrate, (3) bedding confined, and (4) model generated. Previous research considers all relay ramp structures in one population, regardless of scale and structural setting. This study shows that behavior and deformation of relay ramps during fault growth and segment linkage may be better predicted and understood when considered as separate populations.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009