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# GP210 - Labs

Homework Resources
Program Documentation: Descriptions of all SEPlib programs.
Assignment List
Getting to know your data This lab is meant to help you think of data in a physical way rather than a binary one. Keep in mind that the focus of this lab is on your analysis of the data rather than on programming. Lab1_fortran.pdf
Causal and anti-causal integration plus fun with adjoints You are first given a subroutine which performs causal andanti-causal integration. Your task is to code the adjoint and the dot product test to verify that the given anti-causal integration is the adjoint of the causal integration. Then you will have to answer some questions and apply the concept of causal and anti-causal integration. Secondly, you will have several subroutines withthe adjoints removed. The adjoints are also provided, so you simply have to match the correct adjoint with each subroutine.
Normal move-out, multiples and velocity analysis This lab is based on material from Chapters 3 and 4 of BEI. In the first portion you will be asked to select a velocity function that best flattens an NMO gather. In the second portion of the lab you will be given a velocity scan of the same cmp gather and asked to reselect the velocity function. In the final portion you will be given a multiple contaminated CMP gather, and asked to correct it based on both the primary and multiple trend of the data.
Kirchhoff migration In this computer exercise you will modify the Kirchhoff migration and modeling subroutine that was presented in class. First you will limit the propagation angles in the subroutine, and then you will modify the subroutine to handle v(z), also you will limit the aperture in the subroutine, and compare it with angle limitation.
2D FFT In this lab you will modify programs to filter data based on the dip, and use it to process a VSP and remove multiples from a CMP gather.
Phase shift downward and upward continuation In this exercise you are provided with a modified version of the phase shift migration and modeling programs found in Basic Earth Imaging (BEI). The program has been arranged so that it outputs snapshots of a wavefield as it is upward continued and downward continued. This week's programming task will be to add depth-variable velocity to the phase shift program and change Makefile to reduce boundary artifacts.
Time-domain Finite-difference wavefield extrapolation In this exercise you will familiarize yourself with full wave-equation modeling. You will first review the stability and dispersion condition in modeling using the isotropic acoustic wave equation. You will then derive the 8th order coefficients of the Laplacian operator for time-domain finite difference wavefield extrapolation. Finally, you will implement the coefficients and create a movie of the wavefield
Reverse Time Migration The goal of this lab is to get you familiarize with coding wave propagation and reverse time migration (RTM). You will be given a module that contains all the necessary subroutines for RTM. There are two programming tasks for this lab. The ﬁrst task involves completing a subroutine that performs the time-marching using the time-domain ﬁnite diﬀerence (TDFD) algorithm. The second task is to write the main program that uses the subroutines in the propagation module. Finally, with your completed RTM code, you will depth-migrate several pre-stack images of the Sigsbee model.

 SEP Stanford Exploration Project GP Department of Geophysics SES School of Earth Sciences Stanford Stanford University

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