20 Structural Geology and Tectonics in a Quantitative World

Monday, 16 April 2018
1:30 PM - 5:30 PM
Room 275

EXPERIMENTAL ANALYSIS OF THE EFFECT OF GRAIN SIZE DISTRIBUTION ON STICK-SLIP AND CREEP BEHAVIOR

Paper number: 20-7
Program: Theme Sessions
Time: 3:30 PM – 3:50 PM

Authors

Abstract

Fault movement can range from steady creep to seismic stick slip, and a single fault can stick and slip in one section while it creeps in another. Similarly, fault zones can range from discrete planes with fine grained fault gouge to anastomosing shear zones containing large undeformed blocks. We use a physical model to test how differences in size and size distribution of fault material can affect the dynamics of deformation.

We test the effect of grain size distribution on fault behavior using elliptical, acrylic disks of three sizes and a simple shear apparatus with a localized shear plane and energy conserving boundary conditions that do not prescribe the strain rate or force. We systematically vary grain size distribution and record displacement and force with time. Early results show that when only one grain size is used slip events scale with the diameter of the grains, such that our smallest grains approximate creep. When mixed grain sizes are used, slip events fall between the expected magnitude for the smallest and the largest grain size present while the frequency of events is governed by the smallest grain size. Understanding how grain mechanics affect fault behavior will contribute to our overall understanding of why faults do or do not generate earthquakes.

Geological Society of America Abstracts with Programs. Vol. 50, No. 4

doi: 10.1130/abs/2018NC-311957

© Copyright 2018 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.