Preface

Applied geophysics is based on physics principles that collect and interpret data on subsurface conditions for practical purposes, including oil and gas exploration, mineral prospecting, geothermal exploration, groundwater exploration, engineering applications, archeological interests, and environmental concerns. The depth of applied geophysics is shallow, typically from the ground surface to several kilometers deep where economic, cultural, engineering, or environmental concerns often arise. Applied geophysics uses almost all of the current geophysical methods, including electrical, magnetic, electromagnetic, gravimetric, geothermal, seismic, seismoelectric, magnetotelluric, nuclear, and radioactive methods. In applied geophysics, geophysicists are usually required to have a good understanding of math and physics principles, knowledge of geology and computer skills, and hand-on experience of electronic instruments. A geophysicist's routine job includes survey designs, data acquisition, data processing, and data interpretation with detailed explanation of the study.

 This book provides a general introduction to the most important methods of applied geophysics with a variety of case studies. These methods represent a primary tool for investigation of the subsurface and are applicable to a very wide range of problems. Contributors to this book have made an effort to put their ideas into simple terms without forgoing quality. The text covers the state of the art and future directions in relation to applied geophysics.

The principal object of this book is to place all the recent interesting and technical literature in one location, particularly the analysis of seismic responses using nonlinear methods, radiometric mapping of hydrothermal alterations, wave modeling and subsurface seismic imaging, geotechnical modeling with seismic tomography, electrical resistivity tomography, fine-scale depositional system studies with highresolution sequence framework, induced polarization/resistivity applications, and rock physics interpretation in geothermal reservoirs.

I consider this book to be convenient for self-study by engineers and scientists in any discipline related to earth sciences, especially in applied geophysical methods.

> **Ali Ismet Kanlı, PhD**  Professor of Geophysics, Istanbul University-Cerrahpasa, Faculty of Engineering, Department of Geophysical Engineering, Avcilar Campus, Istanbul-Turkey

Chapter 1

Abstract

Advance Wave Modeling and

Subsurface Seismic Imaging

Yasir Bashir and Deva Prasad Ghosh

optimal resolution of seismic imaging.

1. Introduction

1

1.1 Malaysian basin

plane-wave destruction, exploding reflector migration

Diffractions for High-Resolution

Seismic modeling and Imaging for the small-scale feature in a complex subsurface geology such as salt deposit, fracture reservoir, and Carbonate is not casual because of propagated wave affected by many objects once it hits the geologic structure in the subsurface. The principal goal of newly developed seismic modeling & imaging is to get a subsurface image of structural features with greatest sharpness or resolution. Using model dataset the Sigsbee and Marmousi, we illustrate the accuracy of conventional and advance wave modeling techniques. However, in conventional a Finite difference (FD) algorithm is used to generate the data and in advanced wave modeling, the low-rank (LR) approximation is used to acquire zerooffset configuration data. A field dataset from Malaysian basin is re-processed and imaged using diffraction imaging which shows an enhancement in structural interpretation. Furthermore, the results gained from the proposed modeling and imaging approach significantly enhance the bandwidth of the imaged data. Finally, a frequency spectrum shows a recovery of low-frequency from 0 to 60 Hz which is an

Keywords: seismic modeling, finite difference, low-rank, diffraction imaging,

Malaysian basins are structurally complicated because their assessment through different phases of continental accretion, rifting and mountain building. The geology of the Malay Basin is very old and different that the other part of Sarawak and Sabah basin [1]. Geophysical and geological challenges include, fine sand imagery, often beyond seismic resolution; imaging under gas chimney and under carbonates; diffraction imaging; imaging of the internal architecture of the basement; understand the propagation of waves in efficient media and the associated anisotropy; speed analysis and anisotropy; Gas cloud imaging using complete waveform inversion; and multiple elimination [2]. The focus of research in this part of the world is to enhance the image quality of the faults, fracture and karst using diffraction imaging. Figure 1a shows the geographical location of the area which is near to the Borneo main land and a part of Sarawak Basin. Figure 1b is the cross section taken
