Townend, J.; Eccles, J.; Kellett, R.L.; DFDP Seismic Project Team 2018 Whataroa 2016 seismic experiment acquisition report. Lower Hutt, N.Z.: GNS Science. GNS Science report 2016/36. doi:10.21420/G2TK9T.
Abstract: In January 2016, an active source seismic experiment was conducted around the DFDP-2B scientific borehole with the aim of imaging the Alpine Fault and providing velocity information about the overburden and metamorphic basement of the Whataroa Valley. The experiment included a Vertical Seismic Profile (VSP) utilising a slimhole four-stage, three-component geophone string suspended in the accessible top 400 m of the borehole, and the optical fibre cable that had been installed at the time of well completion. These data were acquired with a truck-mounted vibroseis source located at the wellhead (zero-offset), and at a range of locations on profiles radiating away from the well (multi-offset and multi-azimuth). Co-incident with the VSP experiments, surface geophones were deployed on two profiles to record the signals from the vibroseis source. In addition to the two-dimensional profiles, a set of three-component seismometers were deployed in different arrays around the wellhead to record the vibroseis shots in a narrow-azimuth three-dimensional survey. During the two weeks of acquisition, all of the receivers were left to record earthquakes and signals from other natural sources during nights and periods when the vibroseis truck was not operating. The experiment is the first use of an optical fibre cable for distributed acoustic sensing in a research borehole in New Zealand. The optical fibre cable had already been used for repeated temperature sensing so was known to be in satisfactory condition to a depth of 893 m. The acoustic sensing, performed using Schlumberger’s heterodyne Distributed Vibration Sensing (hDVS) equipment, demonstrated that the cable was coupled sufficiently well with the casing to allow detection of the active shots and earthquakes. (auth)
The PDF of the report (124 p.) is accompanied by the following files: