Ben Valentino 1 Eduardo Toledo 2 Eduardo Nobre 2 Luciana Vieira 2 Diogo Cintura 2 1 Department of Earth Sciences SUNY Oswego 2 Department of Civil Engineering Federal University of ID: 414352
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Slide1
Discrete Element Modeling of a Subduction Zone
Ben Valentino
1
, Eduardo Toledo
2
, Eduardo Nobre2, Luciana Vieira2, Diogo Cintura21Department of Earth Sciences, SUNY Oswego2Department of Civil Engineering, Federal University of Alagoas (UFAL)
Conclusion
References
Acknowledgements
Introduction
Theory and Methods
Objective
Results
Subduction
is the process that occurs when the convergence of adjacent tectonic
plates results in one plate overriding the other. This occurs only at oceanic-oceanic
and oceanic-continental plate boundaries. This process has been studied
extensively, but the process of
subduction
initiation remains a controversial topic
(
Geyra
, 2011).
The objective of this study was to successfully model a continental-oceanic
subduction
zone using the discrete element method (DEM) and conjointly to provide insight into the initiation process.
Subduction is a very complex process, hence, modifications to the modeling software were necessary. Therefore it is an equally important objective to develop software capable of modeling a subduction zone using DEM.
The discrete element method utilizes particles which interact with each other under the laws of Newtonian physics. The program PreDEM was used to construct the models. The model is constructed by defining zones, called materials, which are filled with particles. For each material, a spring defines the interaction properties of the particles. A contact model, which controls the stiffness of the spring, is defined for each of the materials. In this study a Kelvin contact model was used. This model controls the tensile and compressional stiffness of the spring in addition to the damping coefficients. Once a model is constructed, the data for the simulation is produced in the program DEMOOP parallel, and the results of the simulation are observed in Demview. Template and dat files were used to implement a BPM to the model in order to strengthen the oceanic and continental crust and to prevent bunching of the oceanic crust.
Of the variables influencing subduction in these models, material density had the most significant impact on subduction of the oceanic crust. Drastic exaggeration of the oceanic crust density lead to the best subduction results, but they are unrealistic. Future modeling will incorporate implementation of a pressure/temperature gradient which varies elasticity with depth and will include thermal differences in the mantle wedges and oceanic/cont. crust. Optimally, these modifications will lead to a lower value for the cont. crust density and cause the oceanic layer to subduct further into the mantle. Once this is achieved, we can begin meaningful investigations of the initiation process of a subduction zone at a cont. margin.
The driving mechanism behind tectonic plate movement is mantle convection. This is the same
mechanism which drives
subduction
. The primary cause for
subduction
initiation is gravitational differences of the oceanic and cont crust, but there are other factors which play a role in the initiation process (
Geyra
, 2011). Once initiation has been achieved, the colder, less buoyant oceanic crust is forced under the hotter, more buoyant cont. crust.
Geyra
,
Taras
.
Future directions in
subduction
modeling:
Journal of Geodynamics V. 52 pp 344-378
The Pacific Northwest Seismic Network, PNSN
http://old.pnsn.org/HAZARDS/CASCADIA/cascadia_zone.html
Image from the Pacific Northwest Seismic Network