Study of the wave scattering in geological environments for the propagation velocity estimation

Abstract

Diffraction is a naturally physical phenomenon which plays an extremely key role in forming some theoretical foundations of analyzing geophysical data such as seismic reflection and high frequency electromagnetic, Ground Penetrating Radar to study geological objects. In this phenomenon, when a wave field propagates from a source to an object with small size or a rough surface, its wave energy receivers act as the secondary sources and send their energy parts back to geophones on the ground surface. The relationship between the wave propagation time and the receiver coordinates is formulated as a diffraction hyperbola. This paper reported examples of the high frequency electromagnetic and seismic scattering phenomena with their applications in the study of the wave propagation velocity, location of civil underground objects and seabed depth. The research on scattering phenomenon for the electromagnetic waves has been known and widely applied; however, studying the wave velocity model by the diffraction analysis from the high resolution reflection seismic data for a fixed source receiver distance can be firstly considered in Vietnam and in the world. To determine the two wave velocity types, two graphs of their energy and entropy attributes were built and then calculated from their Kirchhoff migrated data in velocity ranges in order to find out their attributes’ extremes versus velocity variables. Their migrated sections with correct wave velocities could correctly locate diffractors as underground anomalies and produced the maximum energy and minimum entropy values in the peaks of diffraction hyperbolae and the surrounding zones of the diffractors, respectively. These geophysical data were measured at the urban and coastal area of Can Gio district, Ho Chi Minh city, Vietnam.