Mecanismo Focal (MF)
El mecanismo focal de un terremoto describe la deformación inelástica en la región de la fuente donde se generan las ondas sísmicas. En el caso de un evento producido por fallamiento el MF indica la orientación del plano de falla que se ha deslizado y el vector de deslizamiento, esto también se conoce como "solución del plano de falla". Los mecanismos focales se derivan de la solución del tensor momento de un terremoto, el cual se estima a partir del análisis de las formas de onda sísmicas observadas . El MF puede ser estimado a partir del patrón de "primeros impulsos", es decir los primeros arribos de "onda P" ya sean estos de compresión o dilatación. Este método fue ampliamente utilizado hasta antes de que las formas de onda fueran digitales, y hoy en día aún es útil para obtener una solución simple de del tensor momento de sismos relativamente "pequeños". Hoy en día los MF's son calculados por algoritmos que realizan un análisis semi y automático de las formas de onda.
Dentro de las pocas opciones (q conozco) para dibujar MF's (GMT, ARCGIS, DIP y cualquier editor de gráficos) , esta en particular me parece interesante ya que ofrece una perspectiva 3D simpática, ideal para presentaciones y sobre todo por que se realiza en LaTeX lo cual resulta de utilidad para quienes utilizamos este editor en la redacción de papers o tesis relacionadas a sismologia y afines... A a continuación el código en LaTeX de la "pelotita"... Espero sea de utilidad.
***********
\documentclass[11pt]{article}
\usepackage{tikz}
\usepackage{tikz-3dplot}
%%%<
\usepackage{verbatim}
\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{5pt}%
%%%>
\begin{comment}
:Title: Seismic focal mechanism in 3D view.
:Tags: 3D; Earth Sciences ; Geophysics; Seismology
:Author: Cyril Langlois
:Source: http://math.et.info.free.fr/TikZ/index.html
Adaptation for LaTeX of a figure proposed in P. Shearer's book 'Introduction to Seismology'.
It shows the focal sphere with the fault plane and auxiliary plane (which can
not be discriminate), limiting compression and dilatation quadrants, the first
movement of the rock through the sphere, and the Pression and Tension axis.
The figure is based on the sphere drawing's code proposed by J. Dumas in is
book `Tikz pour l'impatient <http://math.et.info.free.fr/TikZ/>`_, available online.
\end{comment}
%%%%%%%%%%%
%% helper macros
%: Styles for XYZ-Coordinate Systems
%: isometric South West : X , South East : Y , North : Z
\tikzset{isometricXYZ/.style={x={(-0.866cm,-0.5cm)}, y={(0.866cm,-0.5cm)}, z={(0cm,1cm)}}}
%: isometric South West : Z , South East : X , North : Y
\tikzset{isometricZXY/.style={x={(0.866cm,-0.5cm)}, y={(0cm,1cm)}, z={(-0.866cm,-0.5cm)}}}
%: isometric South West : Y , South East : Z , North : X
\tikzset{isometricYZX/.style={x={(0cm,1cm)}, y={(-0.866cm,-0.5cm)}, z={(0.866cm,-0.5cm)}}}
%% document-wide tikz options and styles
\begin{document}
\begin{tikzpicture} [scale=4, isometricZXY, line join=round,
opacity=.75, text opacity=1.0,%
>=latex,
inner sep=0pt,%
outer sep=2pt,%
]
\def\h{5}
\newcommand{\quadrant}[2]{
\foreach \t in {#1} \foreach \f in {175,165,...,5}
\draw [fill=#2]
({sin(\f - \h)*cos(\t - \h)}, {sin(\f - \h)*sin(\t - \h)}, {cos(\f - \h)})
-- ({sin(\f - \h)*cos(\t + \h)}, {sin(\f - \h)*sin(\t + \h)}, {cos(\f - \h)})
-- ({sin(\f + \h)*cos(\t + \h)}, {sin(\f + \h)*sin(\t + \h)}, {cos(\f + \h)})
-- ({sin(\f + \h)*cos(\t - \h)}, {sin(\f + \h)*sin(\t - \h)}, {cos(\f + \h)})
-- cycle;
}
%Quadrants
\quadrant{220,230,...,300}{black}
\quadrant{-60,-50,...,20}{white}
\quadrant{30,40,...,120}{black}
\quadrant{130,140,...,210}{none}
%Movement arrows
\foreach \t in {225,235,...,295}
\foreach \f in {50,40,...,0}
\draw [red, opacity=1.0, ->, thick]
({sin(\f - \h)*cos(\t - \h)}, {sin(\f - \h)*sin(\t - \h)}, {cos(\f - \h)})
-- ({(1 + 0.2*cos(90 - \f))*sin(\f - \h)*cos(\t - \h)},
{(1 + 0.2*cos(90 - \f))*sin(\f - \h)*sin(\t - \h)},
{(1 + 0.2*cos(90 - \f))*cos(\f - \h)});
\foreach \t in {125,135,...,205}
\foreach \f in {110,100,...,0}
\draw [black, ->, thick]
({(1 + 0.2*cos(90 - \f))*sin(\f - \h)*cos(\t - \h)},
{(1 + 0.2*cos(90 - \f))*sin(\f - \h)*sin(\t - \h)},
{(1 + 0.2*cos(90 - \f))*cos(\f - \h)})
-- ({sin(\f - \h)*cos(\t - \h)},{sin(\f - \h)*sin(\t - \h)},{cos(\f - \h)});
\foreach \t in {35,45,...,115}
\foreach \f in {130,120,...,0}
\draw [red, opacity=1.0 ,->, thick]
({sin(\f - \h)*cos(\t - \h)}, {sin(\f - \h)*sin(\t - \h)}, {cos(\f - \h)})
-- ({(1 + 0.2*cos(90 - \f))*sin(\f - \h)*cos(\t - \h)},
{(1 + 0.2*cos(90 - \f))*sin(\f - \h)*sin(\t - \h)},
{(1 + 0.2*cos(90 - \f))*cos(\f - \h)});
\foreach \t in {-55,-45,...,25}
\foreach \f in {130,120,...,0}
\draw [black, ->, thick]
({(1 + 0.2*cos(90 - \f))*sin(\f - \h)*cos(\t - \h)},
{(1 + 0.2*cos(90 - \f))*sin(\f - \h)*sin(\t - \h)},
{(1 + 0.2*cos(90 - \f))*cos(\f - \h)})
-- ({sin(\f - \h)*cos(\t - \h)},{sin(\f - \h)*sin(\t - \h)},{cos(\f - \h)});
%Annotations
\path ({1.5*sin(100)*cos(75)}, {1.5*sin(100)*sin(75)}, {1.5*cos(100)}) node [right] {Compression};
\path ({1.5*sin(70)*cos(-15)}, {1.5*sin(70)*sin(-15)}, {1.5*cos(70)}) node [right] {Dilatation};
\path ({1.25*sin(50)*cos(165)},{1.25*sin(50)*sin(165)},{1.25*cos(50)}) node [left] {Dilatation};
\path ({1.25*sin(30)*cos(255)},{1.25*sin(30)*sin(255)},{1.25*cos(30)}) node [left] {Compression};
%P and T axis
\begin{scope}[ultra thick]
\draw[->] ({1.75*sin(90)*cos(75)}, {1.75*sin(90)*sin(75)}, {1.75*cos(90)})
-- ({2*sin(90)*cos(75)},{2*sin(90)*sin(75)},{2*cos(90)}) node [above] {T-axis};
\draw[->] ({1.75*sin(90)*cos(255)},{1.75*sin(90)*sin(255)},{1.75*cos(90)})
-- ({2*sin(90)*cos(255)},{2*sin(90)*sin(255)},{2*cos(90)}) node [below] {T-axis};
\draw[<-] ({1.5*sin(90)*cos(-15)}, {1.5*sin(90)*sin(-15)}, {1.5*cos(90)})
-- ({1.75*sin(90)*cos(-15)},{1.75*sin(90)*sin(-15)},{1.75*cos(90)}) node [right] {P-axis};
\draw[<-] ({1.5*sin(90)*cos(165)}, {1.5*sin(90)*sin(165)}, {1.5*cos(90)})
-- ({1.75*sin(90)*cos(165)},{1.75*sin(90)*sin(165)},{1.75*cos(90)}) node [left] {P-axis};
\end{scope}
% Label
\node [anchor=north, yshift=-2mm] at (current bounding box.south)
{Seismic focal mechanism and Pression-Tension axis.};
\end{tikzpicture}
\end{document}
*********
No hay comentarios:
Publicar un comentario