Capabilities of High-Resolution Seismic Surveys in Water Areas for Geological Engineering Applications

Abstract

Abstract Today there are a number of challenges related to construction and operation of engineering structures in water areas, especially in shallow regions. This primarily includes installation of platforms for exploratory and production drilling in sea shelf areas, underwater piping work, and construction of engineering structures. Shallow water areas are the most dynamic zones affected by quick sedimentation and active transportation of upper sediments, which can be a hazard to the already constructed structures (for example, in the form of such phenomena as landslides and sand waves). In addition, high-resolution seismic surveys in water areas allow addressing various tasks related to environmental monitoring and comprehensive water area status tracking. There are four groups of geological engineering tasks addressed by high-resolution seismic surveys: 1) obtaining information about the geological section and geometry of geological structures, 2) obtaining information about area distribution of sediment properties, 3) determining physical properties of sediments, and 4) solving geodynamic tasks. Currently the vast majority of seismic engineering surveys in water areas are carried out using either single-channel (1D) or multi-channel (2D) profiling. At the same time, three-dimensional (3D) exploration systems that offer a number of advantages have been used in petroleum geophysics for quite a while. Nevertheless, such systems are utilized for geological engineering applications only in isolated cases. This is mostly due to the need to solve certain hardware-related and methodological problems during field work and subsequent data processing. Seismic data from the near-surface sections are complicated by typical seismic and geological conditions: small acoustic contrast between sediments under bottom as compared to the water and bottom boundary, high seismic energy absorption in bottom sediments, and considerable alteration of sediment properties with depth. Surveys in shallow water areas bring problems associated with multiple waves in target seismic trace times, re-reflection of useful signals from the bottom and the water-air surface etc.