[1] “Hello, World!”
June 5th, 2014
A typical introduction to any programming language will start with one of the more basic functions: printing a simple phrase. Ubiquitously, this phrase is "hello, world!" Whether in C++, FORTRAN, or Python, this hardly ever fails. I figure that there's no better way to begin this blog.
How come? For starters, my project--originally titled "Melt migration and distribution at the lithosphere-asthenosphere boundary and its implications for seismic observations," but altered to "Models of seismic anisotropy around the San Andreas Fault, California" after discussion with my adviser, Dr. Mousumi Roy--involves plenty of coding, and for good reason. My overarching plan for this project is, via Python coding, FEniCS software for partial differential equation solutions, and D-Rex calculations of seismic anisotropy, to construct various models of lithospheric and asthenospheric rheologies in the San Andreas Fault region and their effects on anisotropic orientations of dry olivine-enstatite aggregates in the upper mantle. We observe a stark contrast between northern California and southern California: in northern California, east-west anisotropy dominates far from the transform boundary, and fault-parallel anisotropy dominates in its neighborhood. Meanwhile, in southern California, east-west anisotropy dominates to a greater extent; fault-parallel anisotropy lies only in the immediate vicinity of the fault. Tetreault, Roy, and Gaherty have previously suggested that the former is due to strong lithosphere-asthenosphere coupling, and the latter, weak coupling. They drew their conclusions from variations of viscosities of two layers, emulating the higher-viscosity lithosphere and lower-viscosity asthenosphere, over different time frames. In particular, two-layered viscosity emulates northern data, and isoviscosity emulates southern data. I'm here to verify these observations!
Much of this is new to me, and fairly technical. Faced with the task of eating a whole elephant, I'll adopt the strategy incorporated many times before: taking the whole elephant bit by bit, not all at once, in stafes I can measure. IRIS's suggestion of taking the summer in thirds sounds feasible enough. So, here goes:
-The first third (about 1 June to 27 June): install all required software (Gedit, D-Rex, etc.) on my computer; learn Python and FEniCS from tutorials and code written by previous students under Dr. Roy; author my own code to reproduce growth time of a disturbance as a function of wave number for the Rayleigh-Taylor instability, shown in 6-12 of Turcotte and Schubert's Geodynamics; attend the PyLith workshop at Stanford University from 23 to 27 June.
-The second third (about 28 June to 19 July): complete the first step of the modeling process, accounting for strike-slip plate motion and asthenospheric flow, in both a two-layered scenario with differing lithospheric and asthenospheric viscosities and an isoviscous scenario.
-The third2 (about 20 July to 15 August): apply D-Rex's calculations of seismic anistropic orientation to my models; submit my abstract for AGU (due 6 August); describe the implications of my models in full.
Hopefully, I'll be able to progress past the material I'll attempt to verify and embark into more advanced territory by imposing new constraints on my models.
In the meantime, I'm jumping through various hoops in the UNM bureaucracy so I may gain access to the physics building and internet in the first place. If I vanish, then I've been defeated. Stay tuned, folks.
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