title	expQRTM Manual
date	2021-11
author	Yufeng Wang
mathjax	true

Overview of expQRTM package

expQRTM is a CUDA-based code package that implements $Q$-compensated reverse time migration with explicit stabiization in the time-space domain. This package is provided for verifying the feasibility and stability of the proposed explicit stabilization scheme. We provide two package versions: QRTM_marmousi.cpp for $Q$-RTM on a surface survey with Marmousi model; QRTM_crosswell.cpp for $Q$-RTM on a crosswell survey. The package has been well test on Linux OS (Ubuntu 20.04 TLS) with MPI and CUDA available.

The architecture of expQRTM package

├── input
│   ├── para_crosswell
│   ├── para_marmousi
│   ├── records_crosswell
│   └── records_marmousi
├── output
│   ├── output_crosswell
│   └── output_marmousi
├── examples
│   ├── plot_crosswell
│   └── plot_marmousi
├── Myfunctions.h
├── CQRTM.cpp
├── CUDAQRTM.cu
├── QRTM_crosswell.cpp
├── QRTM_marmousi.cpp
├── Makefile
└── README.md

The input parameters of the package

/input/para_*: accurate velocity and $Q$ model for Marmousi and crosswell examples: - /input/para_marmousi/acc_vp.dat: quasi-Marmousi velocity model; - /input/para_marmousi/acc_Qp.dat: quasi-Marmousi $Q$ model; - /input/para_crosswell/acc_vp.dat: synthetic crosswell $Q$ model; - /input/para_crosswell/acc_Qp.dat: synthetic quasi-Marmousi $Q$ model; - /input/para_crosswell/sx.txt: the x location of sources in grid; - /input/para_crosswell/sz.txt: the z location of sources in grid; - /input/para_crosswell/rx.txt: the x location of receivers in grid; - /input/para_crosswell/rz.txt: the z location of receivers in grid.

The output results of the package

output/output_*: generated results such as seismograms, images of each shot and final stacked images. What we are most interested in is final images, wich includes: - output/output_*/Final_image_cor_type0.dat: image from acoustic RTM; - output/output_*/Final_image_cor_type1.dat: image from viscoacoustic RTM without compensation; - output/output_*/Final_image_cor_type2.dat: image from $Q$-RTM without stabilization; - output/output_*/Final_image_cor_type3.dat: image from $Q$-RTM using explicit stabilization (alpha=1); - output/output_*/Final_image_cor_type4.dat: image from $Q$-RTM using explicit stabilization (alpha=2); - output/output_*/Final_image_cor_type5.dat: image from $Q$-RTM using explicit stabilization (alpha=8);

The examples for plotting the final results

examples/plot_*: scripts for plotting final results, which includes: - examples/plot_*/data: a folder for final results copied from ./output/output_*; - examples/plot_*/madaimage/SConstruct: plot images, velocity and $Q$ models; - examples/plot_*/matlabtrace/martrace: plot extracted trace from final migrated images for comparison.

The C and CUDA files

• Myfunctions.h: header file for the statement of extern "C" functions defined in CUDAQRTM.cu and C functions defined in CQRTM.cpp;
• CQRTM.cpp: C functions file;
• CUDAQRTM.cu: CUDA functions file;
• QRTM_*.cpp: C main function file;
• Makefile: excution script.

Important flags and parameters in QRTM_*.cpp

• Geometry: Geometry=0 for surface seismic survey and Geometry=1 for crosswell seismic survey;
• RTMtype: you can change this flag to generate different migrated images:

	int Geometry=0;		// Geometry=0 for surface seismic survey
					// Geometry=1 for crosswell seismic survey
						
	int RTMtype=0;	// RTMtype=0 for acoustic RTM
			// RTMtype=1 for viscoacoustic RTM without compensation
			// RTMtype=2 for QRTM withou stabilization
			// RTMtype=3 for QRTM using explicit stabilization scheme (alpha=1)
			// RTMtype=4 for QRTM using explicit stabilization scheme (alpha=2)
			// RTMtype=5 for QRTM using explicit stabilization scheme (alpha=8)

• explicit satbiliztion parameters for different RTMtype configurations:

	float alphaorder = 2;	// the default stabilization order;
	float kref = 0.32;	// the reference wavenumber for stabilization;
	float scaling = 0;	// the scaling factor see equation (23) in our paper;
	if(RTMtype==2)
	{
		scaling = 0;
	}
	if(RTMtype==3)
	{
		alphaorder = 1;
		scaling = 1;
	}
	if(RTMtype==4)
	{
		alphaorder = 2;
		scaling = 1;
	}
	if(RTMtype==5)
	{
		alphaorder = 8;
		scaling =1;
	}
	float sigmafactor = scaling*powf(kref, 2*averGamma+1-alphaorder);

Prerequisites

expQRTM package is developed under Linux system, which should be equipped with the following environments: - CUDA environment (cuda-10.2 for example); - MPI environment (openmpi4 for example); - Matlab; - Madagascar.

How to run this package

• Step 1: Confirm the environment in Makefile, and replace the folder path with your own enviroment path;

#! /bin/sh

# set CUDA and MPI environment path 
CUDA_HOME=/usr/local/cuda-10.2	# change this with your own configuration
MPI_HOME=/home/wyf/openmpi4		# change this with your own configuration

INC=-I$(CUDA_HOME)/include -I$(MPI_HOME)/include 
LIB=-L$(CUDA_HOME)/lib64 -L$(MPI_HOME)/lib

• Step 2: Run the Makefile by the command line: make for generating records folder for saving synthetic seismograms;
• Step 3: Run make marmousi for surface seismic imaging on Marmousi model, or run make crosswell for crosswell imaging;
• Step 4: View generated files in the folder ./ouput/output_*;
• Step 5: Plot final results by run /examples/plot_*/madaimage/SConstruct and /examples/plot_*/matlabtrace/martrace.m.

Contact me

I am Yufeng Wang, an associate research professor from China University of Geosciences, Wuhan. If you have any question about this coda package, please feel free to contact me by Email:wangyufeng@cug.edu.cn.

Copyright

expQRTM is a CUDA-based code package that implements Q-compensated reverse time migration with explicit stabiization in the time-space domain. The Marmousi model used in this package is available for download from Madagascar MainPage http://www.ahay.org/data/marm2.

Copyright (C) 2021 China University of Geosciences, Wuhan (Yufeng Wang)

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTI CULAR PURPOSE. See theGNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.