Innovations in seismic sensors driven by the search for gravitational waves

An example is provided of how technology from a seemingly far-removed field of science has found its way into seismic surveying equipment. In order to achieve affordable dense sampling to remove adverse seismic-noise effects from gravitational-wave measurements, autonomous, integrated seismic nodes were developed for flexible deployment around the gravitational-wave detector's key components. The required sensitivity is achieved by utilizing a high-sensitivity, 5 Hz geophone in combination with a low noise recording channel, resulting in a self noise of < 1 ng/√Hz at 1 Hz. This specification is also promising for low-frequency single-sensor passive and active seismic acquisition. Ninety-six nodes were deployed during a field trial to demonstrate various novel passive seismic techniques for subsurface and microearthquake characterization using dense surface arrays. This showed the value of an affordable and practical dense surface array in extracting useful subsurface information from seismic noise and characterizing small earthquakes. The nodes were shown to have the long battery life required to be practical in their intended surveys, showing only 50% battery consumption after a 21-day survey at high-gain setting.