Paper No. 7
Presentation Time: 10:15 AM


STRAYER, Luther M., Earth and Environmental Sciences, California State University East Bay, 25800 Carlos Bee Blvd, Hayward, CA 94542 and SUPPE, John, Department of Geosciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, P.O. Box 13-318, Taipei, 10617, Taiwan,

Critical-taper wedge mechanics (e.g. Davis, et al. 1983, Dahlen 1990) provides a fundamental relationship between fault and wedge strength and the observed tapered geometries of fold-and-thrust belts and accretionary wedges. This theory has provided diverse insight into kinematics, roles of erosion and sedimentation, and the morphology of compressive mountain belts, much of which has been aided by extensive analog and numerical modeling. In contrast, quantitative applications of wedge theory to either nature or models has been rather limited because of the complexity of most wedge equations making it easy to become “lost in parameter space” with many parameters difficult to constrain with real world data. However, wedge theory has been recently recast into a much simpler form (Suppe 2007; Yeh and Suppe 2013) that provides a clear path between observations of the covariation of surface slope α with detachment dip β and the wedge W and fault F strengths, with few assumptions. Here [1] we successfully test this simpler quantitative wedge theory over a very wide range of wedge strengths and structural styles using distinct-element numerical models and [2] we show how we obtain fault and wedge strengths (W, F) directly from observations of surface slope α with detachment dip β in several active thrust belts and accretionary wedges, including the Niger delta, Taiwan, and the Tohoku earthquake offshore of Japan. These observations demonstrate that wedges are strong, but the detachments are very weak, with F/W=0.1 or less.