Evidence-Based Seismic Impact of Wind Farms and Borehole Sensor Performance at the EKA Array

Mitigating Seismic Ground Vibration (SGV) near the EKA/AS104 array at Eskdalemuir is increasingly important as Scotland expands wind farm development to meet its 2045 Net Zero commitments. Based on concerns about potential impacts on CTBT monitoring, the UK MoD currently restricts wind farm development near the EKA array, based on an empirical seismic forecasting model. This model assumes a single point source and relies on empirical attenuation and seismic velocity models. In 2004, via a student research paper the UK-MoD also set a limit on the maximum rms ground displacement of 0.336 nm for wind farm development within 50km of EKA array. Our results show that background seismic noise has significantly increased in the last 20 years due to the development of commercial forestry and anthropogenic activity.

To provide an evidence based assessment, two independent studies were commissioned . The first deployed surface seismic stations in a linear array up to 10 km from an existing wind farm and measured SGV across wind speeds from 0 to over 20 m/s. The data show that no detectable turbine related background seismic noise beyond approximately 5.0 km, demonstrating that real-world conditions differ substantially from the assumptions in the MoD’s model.

A second study drilled and cased a 200 m borehole near the EKR4 array element and installed a modern broadband seismometer, along with two additional sensors at the wellhead for comparison. It is well known that borehole sensors—already standard at many CTBT stations—significantly reduce SGV noise and improves signal quality. Data collected throughout 2025 show reductions of ~10 dB on calm days, and up to 25 dB on windy days within the MoD bandwidth of interest (2 to 8 Hz). The borehole sensor shows a clear improvement in signal-to-noise ratios, resulting in clear P-wave arrivals for teleseismic events. Importantly, the study also found that the original MoD threshold of 0.336 nm limit is routinely exceeded due to forestry activities and other man-made sources.

Thus, these findings demonstrate that wind farms have minimal seismic impact beyond ~5 km of such wind farm and that borehole sensors can substantially enhance the array’s resilience to environmental noise. This evidence supports revising the current MoD moratorium to allow unrestricted wind farm development at distances of not less than ~5 km from the Array. The wind industry has offered to drill and install borehole seismic sensors to supplement EKA elements, further strengthening the array’s capability to detect clandestine nuclear tests in support of the CTBT and reducing SGV from other anthropogenic sources, ensuring the long-term operational integrity of the array.