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No.87 (2009/3) >

 
Title :FE modeling of present day tectonic stress along the San Andreas Fault zone
Authors :Koirala, Matrika Prasad
Hauashi, Daigoro
Authors alternative :林, 大五郎
Issue Date :Mar-2009
Abstract :F E modeling under plane stress condition is used to analyze the state of stress in and around the San Andreas Fault (SAF) System taking whole area of California. In this study we mainly focus on the state of stress at the general seismogenic depth of 12 km, imposing elastic rheology. The purpose of the present study is to simulate the regional stress field, displacement vectors and failures. Stress perturbation due to major fault, its geometry and major branches are analyzed. Depthwise variation from 20 km to 0.5 km is considered for the fault type analysis. Series of calculations are performed with the parametrical variations of domain properties and are applied for the strong/weak SAF. All the simulated results are finally utilized for the implication of present day plate kinematics. Although in nature there is lateral and vertical variation in rheology within single domain and different domains (not considered in this study), our simulated results are comparable with the observed data. The imposed boundary condition (fixed North American plate, Pacific plate motion along N34°W vector up to northern terminus of the San Andreas faults and N50°E vector motion for the subducting Gorda and Juan de Fuca plates) had simulated the present day regional σHmax orientation and displacement vector. Simulated results show some local effect on the stress field and displacement vector by the main strand of the fault and probably its geometry and branch (Garlock Fault). Probably the low angle σHmax orientation to the strike of the SAF system in the South California (although there are some high angle σHmax orientation in southeastern California) compare to the central and northern California is due to the big bend and the Garlock Fault. This modeling had also beautifully simulated the left lateral strike slip movement on the Garlock Fault. Failure analysis performed based on Byerlee's law directly test the strong SAF and variation of physical parameters in the Mohr-Coulomb failure criterion is utilized to test relatively strong/weak SAF. Our simulated results (like stress, displacement vector, and failures) in the weak fault in relatively strong crust conditions has more or less reproduced comparable and theoretically correct results, allowed us to favor weak fault in relatively strong crust. Depthwise variation of the fault type reveal that as the depth increases, the fault types are generally normal and shallow depth gives more strike slip and thrust fault. In conclusion SAF may terminate as a normal fault at the depth.
Type Local :紀要論文
ISSN :0286-9640
Publisher :琉球大学理学部
URI :http://hdl.handle.net/20.500.12000/9529
Citation :琉球大学理学部紀要 = Bulletin of the College of Science. University of the Ryukyus no.87 p.21 -45
Appears in Collections:No.87 (2009/3)

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