Las bifurcaciones en diaclasas secundarias: geometría tridimensional (ejemplos de la Cuenca del Ebro)

Abstract

Forking is the process of fracture bifurcation ¡rito two or more diverging fracture planes. It occurs when a fracture reaches a critical velocity concomitant with its approach to a previous discontinuity. The literature gives a comprehensive 2-D description of forking, and this work presents a 3-D description of these structures. Outcrop observations suggest that the radiant line (line bounding the parent joint and the bifurcated fractures) is curve shaped (like fracture tip while propagation), and the angle between bifurcated fractures remains aproximately the Same all along the vertical dimension of the joint. This geometry results from the influence of both the previous perpendicular joint towards the parent joint forks and the lithologic boundary at top and bottom of the jointed layer