Attribute analysis of GPR and seismic data for material property

CGISS - Boise State University
Attribute analysis of GPR and seismic data for material
property determination
Attribute analysis is a large group of tools used to
quantify variations in amplitude, frequency content,
and phase of a reflected waveform, and to relate
these quantities to the physical properties of the
medium in which the signal is propagating. We
focus on the application of attenuation analysis,
amplitude variation with offset (AVO) analysis, and
phase variation with offset (PVO) analysis. To make
full use of the information extracted through
Figure 1. In this AVO gradient image with wiggle
attribute analysis, it is important to determine the
trace overlay, the large AVO gradient, associated
spatial distribution of attribute anomalies. This
with the top of a gasoline saturated sand, is clearly
requires a detailed understanding of wavefield kine- identified as a zone of red coincident with a high
amplitude reflection.
matics which depend strongly on the velocity field
through which the signal propagates.
Thus, an important component of our
research involves the application of
sophisticated velocity analysis and
imaging tools, such as traveltime inversion and migration velocity analysis, to
GPR and shallow seismic data. Not
only do these tools allow us to pinpoint
Figure 2. Pre-stack depth migrated GPR image over a hydrocarattribute anomalies, but the resulting
bon contaminant plume at Hill AFB, Utah. The velocity model is
shown in the background as a color image. The high velocity
images are used to characterize litholanomaly just above the water table may be associated with a previogy, identify fracture zones, and locate
ously unidentified hydrocarbon rich zone.
buried objects.
There are a wide variety of applications for attribute analysis ranging from aquifer characterization to determination of snow properties. A major focus of our research is direct detection of
groundwater contaminants using GPR. A wide variety of organic contaminants, including chlorinated solvents and many common light hydrocarbons, have electrical properties that differ significantly from water. When these chemicals displace
groundwater a zone of anomalous electrical properties is
formed. This can lead to large GPR AVO gradients and high
electromagnetic velocities (Figures 1 and 2). In snow
research, we use GPR velocity and attenuation to determine
meltwater content and snow density (Figure 3). Attribute
analysis is an exciting area of research that has only recently
emerged in shallow seismic and GPR studies. Continued
development of these methodologies will serve to significantly enhance our ability to understand and characterize the
Figure 3. Acquisition of GPR data for a
shallow subsurface.
snow density study on Pika Glacier, Alaska
Range, AK.
CGISS - Boise State University