[cig-commits] commit: Initial rough draft of the introduction.

[Mercurial]

changeset:   47:9d86546778bc
tag:         tip
user:        Brad Aagaard <baagaard at usgs.gov>
date:        Tue Aug 16 11:23:11 2011 -0700
files:       faultRup.tex
description:
Initial rough draft of the introduction.


diff -r 8aa52e2977e7 -r 9d86546778bc faultRup.tex
--- a/faultRup.tex	Tue Aug 16 09:36:51 2011 -0700
+++ b/faultRup.tex	Tue Aug 16 11:23:11 2011 -0700
@@ -54,71 +54,80 @@ second associated with slip at a point d
 second associated with slip at a point during earthquake rupture to
 thousands of years of strain accumulation between earthquakes. The
 complexity of dealing with the many physical processes operating over
-this vast range of scales generally leads most researchers to narrow their
-focus to a narrow space-time window in order to isolate just one or a few
-processes. Limited spatial and temporal coverage of observations also
-drives researchers to narrow the focus of their studies. 
+this vast range of scales generally leads most researchers to 
+focus on a narrow space-time window in order to isolate just one or a few
+processes; the limited spatial and temporal coverage of observations also
+justifies this narrow focus.
 
 Researchers have recognized for some time, though, that interseismic
-deformatino and fault interactions influence earthquake rupture
+deformation and fault interactions influence earthquake rupture
 propagation, and the dynamics of rupture propagation, in turn, affect
 postseismic deformation. In most cases one simplifies some portion of
-the process to expedite the modeling results. For example, studies of
-slow deformation associated with interseismic and postseismic behavior
-often approximate coseismic slip with the static offset [CITE SOME
-PAPERS]. Likewise, studies of radid deformation associated with
-earthquake rupture propagation often approximate the loading of the
-crust via simplistic assumptions about the stress field at the
-beginning of a rupture [CITE SOME PAPERS]. Earthquake simulators,
-which attempt to model multiple earthquake cycles, simplify not only
-the fault loading and rupture propagation but also the physical
-properties in order to make the calculations tractable.
+the process to expedite the modeling results of another portion. For
+example, studies of slow deformation associated with interseismic and
+postseismic behavior often approximate dynamic rupture behavior with the static
+coseismic slip [CITE SOME PAPERS]. Likewise, studies of radid deformation
+associated with earthquake rupture propagation often approximate the
+loading of the crust via simplistic assumptions about the stress field
+at the beginning of a rupture [CITE SOME PAPERS]. Earthquake
+simulators, which attempt to model multiple earthquake cycles,
+simplify not only the fault loading and rupture propagation but also
+the physical properties in order to make the calculations tractable
+[CITE SOME PAPERS].
 
-Recently, several studies have attempted to broaden the space-time
-window in order to remove simplifying assumptions and more
+Recently, several studies have attempted to examine a broader
+space-time window in order to remove simplifying assumptions and more
 accurately capture the complex interactions over the earthquake
-cycle. [ADD EXAMPLES]
+cycle. [ADD EXAMPLES, Lapusta, Duan/Oglesby, Kaneko].
 
+Collectively, these studies suggest a set of desirable features for
+models of the earthquake cycle in order to capture both the slow
+deformation associated with interseismic behavior and the rapid
+deformation associated with earthquake rupture propagation. These include
+the general capabilities of modeling elasticity with elastic,
+viscoelastic, and viscoelastoplastic deformation, as well as slip on
+faults via either prescribed ruptures or spontaneous ruptures
+controlled by a fault constitutive model. Additionally, a model might
+also include the coupling of elasticity to fluid and/or heat flow.
 
+Our long-term objective is to develop modeling software with these
+capabilities in order to simulate the earthquake cycle, resolving the
+deformation across as wide of a range of temporal and spatial scales
+as possible to avoid simplifications that affect earthquake cycle
+behavior. Our current focus is developing a modeling code, PyLith,
+that supports both quasi-static simulations of interseismic and
+coseismic deformation and dynamic simulations of earthquake rupture
+propapgation. We plan to seamlessly couple these two types of
+simulations together to resolve the earthquake cycle.
 
+Other compelling reasons led us to develop such a code with the
+capability to model both interseismic deformation and earthquake
+rupture propagation. Both types of simulations require the same basic
+infrastructure: importing of models from mesh generators, parallel
+data structures for finite-elements, bulk constitutive models for
+elasticity, fault implementations for prescribed slip and fault
+constitutive models, and output of the solution and state variables
+over the domain. The two types of simulations tend to use different
+boundary conditions, with interseismic deformation usually driven by
+Dirichlet (displacement/velocity) or Neumann (traction) boundary
+conditions and rupture propgation simulations using absorbing
+boundaries to truncate the domains. However, these features constitute
+a small fraction of the code. The primary different between the two
+types of simulations is the time integration scheme, with an
+implicit scheme used in the quasi-static simulations and an explicit
+scheme used in the dynamic simulations; this also results in using
+different solvers as we will discuss later.
 
-model earthquake cycle; slow deformation associated with interseismic
-behavior and coseismic slip; rapid deformation associated with earthquake rupture
-propagation; want general capabilities of modeling elasticity with
-slip on faults, including elastic, viscoelastic, and
-viscoelastoplastic deformation and prescribed slip and/or spontaneous
-rupture controlled by fault constitutive model. 
-
-[mention PyLith somewhere in here]
-
-Our long-term objective is to develop the tools necessary to simulate
-the earthquake cycle, resolving the deformation across as wide of a
-range of temporal and spatial scales as possible to avoid
-simplifications that affect earthquake cycle behavior. Our current
-focus is developing the software that supports both quasi-static
-simulations of interseismic and coseismic deformation and dynamic
-simulations of earthquake rupture proapgation, which we will later
-couple together to resolve the earthquake cycle.
-
-infrastructure associated with parallel data structures for
-finite-elements, bulk constitutive models for elasticity, fault
-implementations for prescribed slip and fault constitutive models, and
-boundary conditions are essentially the same for these two
-problems. The time integration scheme is the primary difference
-between the two types of simulations, with an implicit scheme used in
-the quasi-static simulations and an explicit scheme used in the
-dynamic simulations; this also results in using different solves as we
-will discuss later.
-
-A large component of the infrastrure needed for these simulations,
-which also differentiates these types of problems from many other
-elasticity problems, involves implementing the slip on the fault surface,
-which is interior to the domain. Furthermore, we want the flexibility
-to either prescribe the slip on the fault or have the fault slip
-evolve according to a fault constitutive model that specifies the
-friction on the fault surface. This has affected the overall design of 
-PyLith and all steps in the simulation process, from preprocessing of
-the finite-element mesh through writing the output files.
+Implementing slip on the potentially nonplanar fault surface
+differentiates these types of problems from many other elasticity
+problems. Complexities arise because earthquakes potentially involve
+offset on multiple, intersecting irregularly shaped fault surfaces in
+the interior of the domain. Furthermore, we want the flexibility to
+either prescribe the slip on the fault or have the fault slip evolve
+according to a fault constitutive model that specifies the friction on
+the fault surface. Here, we describe a robust yet flexible method for
+implementing fault slip, its affect on the overall design of PyLith,
+and verification of its implementation using a few benchmarks.
 
 % ------------------------------------------------------------------
 \section{Model}