# FORWARD MODELING CODES

# I. Traveltime Modeling Codes

## 1. Ray Tracing for 2-D and 3-D Media

### Author: Yonghe Sun (1991)

### Tracing transmission rays in 2-D and 3-D slowness media.

"ray3.f" = ray tracing code;
"rays.f" = subroutine code;

#### "demo.1d" = 1-D input & output demo;
"demo.3d" = 3-D input & output demo.

## 2. Traveltime Calculation in a 2-D TI Medium by Huygens' Principle

### Author: Fuhao Qin (1992)

### Traveltime calculation for quasi-P, quasi-SV and SH waves in a (2-D) TI medium by Huygens' principle.

"aneik.f" = traveltime computing code;
"anmod.f" =model builder;

"aneik.in" ; "anmod.in" = input files.

## 3. Finite-Difference Solution to the 2-D Eikonal Equation

### Author: Fuhao Qin (1992)

### First arrival traveltime calculation for 2-D isotropic media.

"eik.f" = traveltime computing code;
"ineik" = input file;

#### "mod.f" = model builder;
"inmod" = input to mod.f.

## 4. Finite-Difference Solution to the 3-D Eikonal Equation: Version 1.0

### Authors: Wenying Cai and Fuhao Qin (1991)

### Computing traveltimes in 3-D isotropic media by a finite-defference solution to the 3-D eikonal equation.

"eik3d.f" = traveltime computing code;
"eik3d.in" = input file;

## 5. Finite-Difference Solution to the 3-D Eikonal Equation: Version 1.1

### Updated by Jianming Sheng, Min Zhou and Chaiwoot Boonyasiriwat (2006)

### Computing traveltimes in 3-D isotropic media by a finite-defference solution to the 3-D eikonal equation.

"main.f" = the main program;

"front3d.f" = 3D Eikonal solver subroutines;

"model_param.h" = Model parameter file;

"Makefile" = GNU Makefile for this package;

"viewtime.m" = Matlab script for viewing the traveltime file;

#### "time.png" =Image of the 3D traveltime produced by Matlab;

## 6. Shortest path Matlab codes

### Author: Ruiqing He (2002)

### Computing first arrival traveltime.

"Mray.m" = Matlab source code;

# II. Wavefield Modeling Codes

## 1. Finite-Difference Solution to the 2-D Acoustic Wave Equation

### Authors: Jerry Schuster (1989) and Jinlong Xu

### Modeling of 2-D borehole acoustic synthetic seismograms by a 2-4 finite-difference solution to the 2-D acoustic wave equation.
The accuracy is 2nd-order in time and 4th-order in space, and code can handle
irregular free-surfaces.

"pp4.f" = modeling code;
"indat" = input file;

#### "mod.f" = model builder;
"inmod" = input to mod.f;

#### "doconvert" = execution file to call convert code;

#### "ftsu.f" = convert code which can be used to conver Fortran unformatted data to SU format data or reverse;

#### "segy.com" = include file for convert code;

#### "ftr.dat.in" = input file for convert code, contains trace number and sample interval;

## 2. Finite-Difference Solution to the Axisymmetric Acoustic Wave Equation

### Author: Jinlong Xu (1993)

### Modeling of axisymmetric borehole acoustic synthetic seismograms by a 2-4 finite-difference solution to the axisymmetric acoustic wave equation. The accuracy is 2nd-order in time and 4th-order in space.

"pp425.f" = modeling code;
"indat" = input file;

#### "mod.f" = model builder;
"inmod" = input to mod.f.

## 3. Finite-Difference Solution to the 3-D Acoustic Wave Equation

### Author: Kim Bak Olsen (1992)

### Modeling of 3-D acoustic synthetic seismograms by 2-4 finite-difference solution to the 3-D acoustic wave equation. The accuracy is 2nd-order in time and 4th-order in space.

"fd3dac.f" = modeling code;
"hom3d.f" = earth model builder;

## 4. Finite-Difference Solution to the 2-D P-SV Wave Equation

### Authors: Yi Luo, Jerry Schuster (1989) and Jinlong Xu

### Modeling of 2-D P-SV synthetic seismograms by a 2-4 finite-difference solution to the 2-D elastic wave equation. The accuracy is 2nd-order in time and 4th-order in space.

"psvr4.f" = modeling code;
"indat" = input file;

#### "mod.f" = model builder;
"inmod" = input to mod.f.

## 5. Finite-Difference Solution to the 2-D SH wave Equation

### Author: Jinlong Xu (1992)

### Modeling of 2-D SH elastic synthetic seismograms by a 2-4 finite-difference solution to the 2-D SH elastic wave equation. The accuracy of the code is 2nd-order in time and 4th-order in space. This program can also model the SH response of free-surfaces with irregular geometry.

"sh4.f" = modeling code;
"indat" = input file;

#### "mod.f" = model builder;
"inmod" = input to mod.f.

## 6. Finite-Difference Solution to the 2-D TI Elastic Wave Equation

### Author: Fuhao Qin (1992)

### Modeling of TI elastic synthetic seismograms by a 2-4 finite-difference solution to the 2-D TI elastic wave equation. The accuracy is 2nd-order in time and 4th-order in space.

"an2dh.f" = modeling code(Z);
"an2dv.f" = modeling code(X);

#### "inmod" = input to mod.f.

## 7. Finite-Difference Solution to the 3-D Elastic Wave Equation (Cray)

### Author: Kim Bak Olsen (1991)

### Modeling of 3-D synthetic seismograms by a 2-4 finite-difference solution to the 3-D elastic wave equation, optimized for CRAY supercomputers with a Solid State Device (SSD). The accuracy is 2nd-order in time and 4th-order in space.

"fd3d2.f" = modeling code;
"hom3d.f" = model builder;

## 8. Finite-Difference Solution to the 3-D Elastic Wave Equation (IBM)

### Author: Kim Bak Olsen (1991)

### Modeling of 3-D synthetic seismograms by a 2-4 finite-difference solution to the 3-D elastic wave equation, optimized for multi processor IBM3090 supercomputers with Extended Memory and is set up for an MVS enviroment. The accuracy is 2nd-order in time and 4th-order in space.

"table' ; "in3d" = input files;

## 9. Separation of 2-D P-Waves and S-Waves

### Author: Kim Bak Olsen (1991)

### Separation of a 2-D elastic wavefield into P-energy and S-energy.

"sep.f" =separation code.

## 10. Finite-Difference Solution to the 2-D P-SV Wave Equation Using An Adaptive Grid

### Author: Xu Ji (1994)

### Modeling of 2-D P-SV synthetic seismograms by a 2-4 finite-difference solution to the 2-D elastic wave equation using the adaptive grid method. The accuracy is 2nd-order in time and 4th-order in space.

#### "mod.f" = model builder;
"model" = input to mod.f;

## 11.Finite-Difference Solution to the 2-D Acoustic Wave Equation Using An Adaptive Grid

### Author: Yue Wang (1996)

### Modeling of 2-D acoustic pressure synthetic seismograms by a 2-4 adaptive staggered grid solving finite-difference solution to the 2-D acoustic wave equation. The accuracy is 2nd-order in time and 4th-order in space.

#### "ap4.f" = modeling code;
"indat" = input file;

#### "mod.f" = model builder; "ap4.inc" = include file.

## 12. Finite-Difference Solution to the Axisymmetric Viscoelastic Wave Equation

### Author: Yue Wang (1995)

### Modeling of axisymmetric viscoelastic synthetic seismograms by a 2-4 staggered grid finite-difference method. The accuracy is 2nd-order in time and 4th-order in space.

## 13. Finite-Difference Solution to the 2-D P-SV Wave Equation Using An Adaptive Grid with Conservation Flux Condition

### Author: Yue Wang (1996)

### Modeling of 2-D P-SV synthetic seismograms by a 2-4 finite-difference solution to the 2-D elastic wave equation using the adaptive grid method with conservation flux condition. The accuracy is 2nd-order in time and 4th-order in space.

#### "ae2d.f" = modeling code;
"indat" =input file;

# III. Electromagnetic Finite-Difference Modeling

## Finite-Difference Solution to the 2-D Maxwell's Equation

### Author: Jerry Schuster and Wenying Cai (1990)

### Modeling of 2-D synthetic electrograms by a 2-4 staggered finite-difference solution to the 2-D Maxwell's equation. The accuracy is 2nd-order in time and
4th-order in space.

#### "em2d.f" = modeling code;
"mod.f" = model builder;

#### "indat" = input file;
"inmod" = input to mod.f.