Subsurface fracture measurement with polarimetric borehole radar

Takashi Miwa, Motoyuki Sato, Hiroaki Niitsuma

Research output: Contribution to journalArticlepeer-review

73 Citations (Scopus)

Abstract

In this paper, a full-polarimetric borehole radar system is presented with combinations of dipole antennas and axial slot antennas and is applied to subsurface fracture measurement. First, to determine a scattering matrix from measurements with antennas having different antenna transfer functions between orthogonal polarizations, we present an antenna compensation algorithm that is achieved by an inverse filtering method with the antenna transfer functions experimentally determined by crosshole measurements. The results of crosshole and single-hole measurements carried out in granite at the Kamaishi Mine are shown to verify the proposed method. In the crosshole measurement, we find that the used dipole and slot antennas have almost the same radiation pattern and frequency dependency from 50 to 120 MHz. The transmission matrices through the host rock are the unit matrix for most paths, while depolarization is observed in some sections. Reflections from subsurface fractures show significant depolarization in the polarimetric single-hole reflection measurements. Using the scattering matrix, it is evaluated that subsurface fractures have a randomly isotropic rough surface for wavelengths between 1 and 2 m on the rotation of polarization basis.

Original languageEnglish
Pages (from-to)828-837
Number of pages10
JournalIEEE Transactions on Geoscience and Remote Sensing
Volume37
Issue number2 I
DOIs
Publication statusPublished - 1999

Keywords

  • Borehole radar measurements
  • Polarimetric system design
  • Radar polarimetry
  • Rough surface
  • Underground object detection

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Earth and Planetary Sciences(all)

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