Imaging the permeability-porosity structure within the near-surface
sediments of Tokyo by acoustic crosswell tomography
Tokuo Yamamoto
Geoacoustics Laboratory, RSMAS, University of Miami, Miami, FL 33149, USA.
e-mail: tyamamoto@rsmas.miami.edu
Abstract
The Kobe Earthquake was a recent reminder that near surface sediments are liquefied by
earthquakes. Liquefaction is a major cause of building and infrastructure damages. It is a challenge
of geophysicists to come up with a remote sensing method to image the permeability-porosity structure
within the near surface sediments. The author has presented an example of successful images of the
permeability-porosity structures of limestone formations at SEG98, and another example of successful
permeability-porosity image of a sandstone oil field at SEGJ98. In these cases, the velocity-attenuation
fields measured by the patented pseudo-random binary sequence (PRBS) acoustic tomography method
were inverted for the permeability-porosity structures using the analytical inverses of the super-k theory
(Yamamoto, 1998), and the squirt-flow theory, respectively. Excellent agreements were shown between
acoustic images and Schlumberger logs and pumping tests.
In this paper, the velocity-attenuation fields measured by the PRBS crosswell tomography are
inverted for the permeability-porosity images within the near-surface sediments of Tokyo. Analytical
closed form expressions for the permeability and porosity are obtained as the inverse of velocity-
attenuation by the Biot theory. The acoustically imaged permeability-porosity structures agree
excellently with the engineering logs and cores.
The proposed acoustical method of permeability-porosity imaging will be useful for establishing
the liquefaction potential of the near-surface sediments to be used for improvement of the foundations
before earthquakes.
raeg98@tansa.kumst.kyoto-u.ac.jp
Last modified: Mon Sep 21 09:24:29 1998