LONG DOES IT TAKE TO REACH A STEADY STATE STRESS? By

• Main Authors: Lokranjith K Ravi, Dr. Keith Rouch, Dr. Shelley, J. Kenner
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Rifting; cycle-up; finite element analysis; Iceland; user-subroutine. Lokranjith K Ravi; Krafla
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.425.1535; http://lib.uky.edu/ETD/ukymeen2005t00234/newranjiththesis.pdf

Many geological numerical models are initiated with a background stress state of zero. Often these numerical results are compared directly to geodetic data. Recent work (Kenner and Simons, 2004) has shown that modeled deformation rates can change as the model is ‘cycled-up ’ following repeated earthquakes or rifting events. In this study, we investigate model cycle-up in the context of time-dependent deformation following rifting during the 1975-1984 Krafla eruption in Iceland. We consider the number of rifting cycles required for complete cycle-up, variations in cycle-up time at different locations in the model, background stress magnitudes in fully cycled-up models, and errors incurred when the models are not properly cycledup. The modeling is done using the commercial software ABAQUS. In ABAQUS a user-defined subroutine is used to apply repeated rifting events within the finite element model. We have generated various 3D models with different fault/rift geometries. The models include (1) a straight rift oriented perpendicular to the farfield velocity boundary conditions, (2) a rift oriented at an angle to the far-field velocities, (3) a model containing two intersecting rifts, one perpendicular to the farfield