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2007 GSA Denver Annual Meeting (28–31 October 2007)

Paper No. 5
Presentation Time: 2:45 PM

DISTINCT ELEMENT MODELLING OF STRUCTURAL EVOLUTION IN OROGENIC WEDGE


PARK, Youngdo, Research Division, Heesong Geotek, Woolim Lion’s Valley 2-cha building, 146-8 Sangdaewon 1- dong, Jungwon-ku, Seongnam-si, 462-807, South Korea and KWON, Sanghoon, Department of Earth System Sciences, Yonsei University, 134 Shinchon-dong, Seodaemoon-ku, Seoul, 120-749, South Korea, youngdo.park@gmail.com

We have used distinct element method (DEM with a code name, PFC2D developed by Itasca CG) to numerically simulate the sandbox for orogenic wedge evolution. DEM is a method for solving mechanical problems of discontinua with particulate data structures and boundary-condition elements. Stored energy in elastically compressed particles with Hookean or Hertzian behavior is the driving force for motions of particles.

A numerical sandbox is constructed for modelling formation and evolution of an orogenic wedge. Angular grains are used to fill the numerical sandbox since these grains tend to suppress free rolling and sliding. The biggest advantage of a numerical sandbox over a physical sandbox is that forces are seen, instead of guessed, in a numerical sandbox. The observed forces are combined with kinematic observations for the interpretation of structural development and evolution. We have focused on two aspects; (1) formation of critically tapered wedge and (2) structural development during and after incipient faulting.

From the experiments related to critically tapered wedges, it is found that the sum of topographic slope and decollement dip remains constant while decollement dip varies from 0 to 10 degrees. This is the similar results as predicted by Mohr-Coulomb wedge model of Davis et al. (1983). However, a slight rate-dependence of the summed angle is observed as we change the velocity of backstop, and we are investigating the reasons. From the experiments related to structural development, we found that incipient faulting occurs in break-forward sequence, which is also commonly observed in many orogenic belts. We are currently studying imbrication-related pattern formation as well as structural evolution related to faulting at thrust wedge.

We believe numerical sandbox experiments can provide more quantitative results than the physical sandbox experiments that can help to understand the kinematics and mechanics, with known structural geometries, during the wedge evolution.

Session No. 48

T110. Combining Kinematics and Mechanics in Understanding Deformation Processes
Sunday, 28 October 2007: 1:30 PM-5:30 PM
Geological Society of America Abstracts with Programs. Vol. 39, No. 6, p.127
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