Normal fault interaction and relay ramp development on the volcanic tableland, E. California

• Main Author: McFadzean, Peter James
• Published: University of Edinburgh 2002
• Subjects: 551.8
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.666196

Fault arrays and relay ramps on the Volcanic Tableland, E. California, USA, are surveyed with a view to assessing the manifestation of fault interactions on fault displacement profiles and the controls on varying strengths of interaction. Surveyed faults are several hundred metres to several kilometres in length with up to tens of metres of displacement. The maximum displacement (D_max): length (L) ratio of a fault segment, extracted from survey data, is used as a guide to a faults interaction state. Rock mass heterogeneities, fault linkage, and fault interaction at both tips are shown to obscure evidence of profile asymmetry, a previously commonly used interaction indicator. Fault growth in isolation is quantitatively re-defined in this study as those faults separated from their nearest neighbour by greater than 0.1*L_t, where L_t refers to the combined length of the two faults under consideration. This is evidenced by an increase in fault D_max:L ratios with decreasing separation distances below 0.1*L_t, and an independence of D_max:L ratios on separation distances above this threshold. D_max:L ratios show a broad positive correlation with overlap (O):separation (S) ratio, indicative of increasing fault interaction with increasing overlap. A length normalised O:S plot reveals a wedge-shaped area along the overlap axis devoid of data points. This suggests O:S ratios are restricted such that faults are only capable of attaining increasing overlap by increasing the separation distance between a fault pair. This in turn implies the existence of stress shadows that scale with the final fault dimensions. Stress perturbations created in the crust from individual slip events may thus be able to accumulate to some degree over multiple slip cycles.