A Modern Reinvestigation of the 1987 Moutere Depression Seismic Survey Justin Chen Lo A thesis submitted for the degree of Master of Science At the University of Otago, Dunedin, New Zealand. Table of Contents Abstract .................................................................................................................................................. iv Acknowledgements ................................................................................................................................ vi 1.0 Introduction ...................................................................................................................................... 1 1.1 Project Aim .................................................................................................................................... 1 1.2 Geological Background ................................................................................................................. 2 1.2.1 Moutere Depression .............................................................................................................. 2 1.2.2 Moutere Gravels & Glen Hope Formation ............................................................................. 2 1.2.3 Western Province ....................................................................................................................... 3 1.2.4 Eastern Province .................................................................................................................... 3 1.2.5 South of Nelson ...................................................................................................................... 4 1.3 Seismic Hazard Considerations ..................................................................................................... 5 1.4 Data Processing: 1980 to Present ................................................................................................. 8 1.5 Original Seismic Data .................................................................................................................. 10 2.0 Seismic Theory ................................................................................................................................ 12 2.1 Seismic Waves, Wave Propagation and Simple Seismic Models ................................................ 12 2.2 Attenuation ................................................................................................................................. 16 2.3 Elastic deformation ..................................................................................................................... 19 2.4 Elastic Constants ......................................................................................................................... 20 2.5 Body waves ................................................................................................................................. 24 2.5.1 P-waves ................................................................................................................................ 25 2.5.2 S-waves ................................................................................................................................ 26 2.6 Surface Waves ......................................................................................................................... 27 2.7 Huygen’s principle ....................................................................................................................... 28 2.8 Snell’s Law ................................................................................................................................... 29 2.9 Zoeppritz Equations .................................................................................................................... 31 2.10 Partition coefficients ................................................................................................................. 32 3.0 Seismic Method .............................................................................................................................. 33 3.1 Seismic Reflection Method ......................................................................................................... 33 3.2 Seismic Resolution: The Fresnel zone ......................................................................................... 36 3.3 Velocities ..................................................................................................................................... 39 3.4 Common Mid-Point Method (CMP) ............................................................................................ 39 3.5 Fourier Transforms...................................................................................................................... 42 3.5.1 Fast Fourier Transform (FFT) ................................................................................................ 46 3.6 Vibroseis ...................................................................................................................................... 46 i 4.0 Processing Sequence (1987) ........................................................................................................... 49 4.1 Initial Processing ......................................................................................................................... 49 4.2 Crooked Line Analysis ................................................................................................................. 50 4.3 Common Depth Point Gathers .................................................................................................... 53 4.4 Deconvolution ............................................................................................................................. 54 4.5 Elevation static correction .......................................................................................................... 57 4.6 Normal Move-Out Dynamic Corrections .................................................................................... 58 4.7 Pre-Stack Mute............................................................................................................................ 60 4.8 Amplitude Modulation ................................................................................................................ 60 4.9 Refraction Static Corrections ...................................................................................................... 61 4.10 CDP Trim and Stack ................................................................................................................... 61 4.11 Time Variant Bandpass Filtering and Time Variant Scaling....................................................... 62 4.12 Migration................................................................................................................................... 62 4.13 Adaptive K-F Filtering ................................................................................................................ 64 5.0 New Processing Flow and Line 01 Results ...................................................................................... 67 5.1 Line 01- initial notes .................................................................................................................... 69 5.2 Adding Geometry ........................................................................................................................ 69 5.3 Floating Datum Application ........................................................................................................ 73 5.4 Pre-stack processing Trace Removal ........................................................................................... 74 5.5 Brute stacking ............................................................................................................................. 81 5.6 First Breaks .................................................................................................................................. 84 5.7 AREAL Module ............................................................................................................................. 87 5.8 Refraction Statics ........................................................................................................................ 90 5.9 Gain ............................................................................................................................................. 97 5.10 Initial refraction mute ............................................................................................................. 103 5.11 Noise Suppression Testing ...................................................................................................... 106 5.12 Comparisons ........................................................................................................................... 114 5.13 Deconvolution Parameter Testing .......................................................................................... 120 5.14 Bandpass Filter Parameter Testing ......................................................................................... 127 5.15 Compilation ............................................................................................................................. 135 5.19 Velocity Analysis...................................................................................................................... 139 5.20 Residual Static Analysis ..........................................................................................................