(Woods Hole Oceanographic Institution, 2006-02)
Stephen, Ralph A.; Pettigrew, Tom; Becker, Keir; Spiess, Fred N.
The purpose of this meeting was to explore design options to simultaneously acquire borehole
seismic data and hydro-geological data (pressure, temperature, fluid sampling and
microbiological sampling) on a single CORK system. The scientific focus was to add a seismic
component to the Juan de Fuca Hydrogeology program. By permanently installing a sensor
string in the borehole our goal was to enable: l) time-lapse VSP's and offset VSP's with
sufficient data quality to study amplitude versus offset, shear wave anisotropy, and lateral
heterogeneity; 2) monitoring of micro- and nano- earthquake activity around the site for
correlation with pressure transients. Because of the difficulty in ensuring adequate coupling
through multiple casing strings we concluded that it was impractical to install the vertical seismic
array with 10m spacing (50-60 nodes) that would be necessary for VSP's and time-lapse VSP's.
We did describe a scenario for a vertical seismic array with approximately 100m spacing (5-6
nodes) that could be used for offset-VSP's and seismic monitoring. This uses some unique
technology and involves two seismic strings: one in the annulus between the 4- 1/2" and 10-3/4"
casings and one in the middle of the 4-1/2" casing.
