EGU25-10925, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-10925
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Seismic While Drilling with a Diamond Core Drill Bit during ICDP Expedition 5071_1_A (DIVE) in the Ivrea-Verbano Zone (Western Alps, Italy)
Bernd Trabi, Florian Bleibinhaus, and Andrew Greenwood
Bernd Trabi et al.
  • Leoben, Applied Geosciences and Geophysics, Chair of Applied Geophysics, Leoben, Austria (bernd.trabi@unileoben.ac.at)

A Seismic While Drilling (SWD) experiment, using a diamond impregnated drill bit has been conducted within the framework of the ICDP expedition 5071, Drilling the Ivrea-Verbano zonE (DIVE), during the drilling of borehole 507_1_A into the lower continental crust of the Ivrea zone (Megolo, Piedmont, Italy). The rotational grinding action of the diamond drill bit on the rock acts as a seismic source within the borehole. Ideally, this would enable real-time imaging of the subsurface directly around the drill bit without the need for separate active seismic surveys. This vibrational signal is known to be weak and the SWD experiment aims to evaluate the potential and limitations of the SWD method for such diamond core drilling commonly used in scientific drilling projects. The study focuses on fundamental developments of the methodology and data processing techniques. For the experiment, 45 three-component sensors were deployed at a 10-m-spacing along a straight line at the surface. The drill rig is located on top of a ca. 60-m-thick sedimentary wedge overlying the hard rocks of interest. The sensor line is approximately 50 m offset from the drill rig and runs entirely on bedrock. Passive seismic data were recorded from mid-November 2023 to late March 2024 at a sampling rate of 1 ms, with the drilling operation reaching a depth of almost 910 m. The seismic data are heavily contaminated by coherent and random noise generated at the drill site, including rig engines, mud-pumps, vehicles, and the handling of equipment. As a first step, we aim to spatially detect the (known) drill bit position using seismic interferometry and migration (back-projection). Cross-coherence interferograms were computed in 30-second time windows and then stacked to enhance the signal-to-noise ratio. Instead of summing the migrated signals, we use the semblance of the signals. The major noise sources that are imaged with the passive seismic data are the vibrations of the drill rig, which appear to mask the weaker signal from the drill bit. For comparison, we also conducted a reverse vertical seismic profile (RVSP) experiment with a borehole sparker source deployed in a depth range between 65 and 305 m. For this depth range, the RVSP data provide velocity constraints required for the imaging. The velocity model derived from the RVSP data likely improves the localization of the drill bit. Since seismic wave propagation is sensitive to velocity variations, having more accurate velocity constraints reduces ambiguity in the migration and interferometry steps. The clear signals from the sparker also help to validate the method under more controlled and favourable conditions. The detection of the (known) sparker position was done using the same method as for the drill bit, with the advantage that the sparker signal is not contaminated by noise sources from the drilling operation.

How to cite: Trabi, B., Bleibinhaus, F., and Greenwood, A.: Seismic While Drilling with a Diamond Core Drill Bit during ICDP Expedition 5071_1_A (DIVE) in the Ivrea-Verbano Zone (Western Alps, Italy), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10925, https://doi.org/10.5194/egusphere-egu25-10925, 2025.