Long-term monitoring with spring-based gravimeters: tilt-control benefits and application to the Rochefort Cave Laboratory (Belgium)

<p>Spring-based gravimeters are light and easy to install, with a precision around 5 &#956;Gal/&#8730;Hz. However, they are still not used for long-term gravity monitoring. The main reason for that is the non-linear drift of those instruments, which is very difficult to correct without removing geophysical signals. We will show that when the tilt is actively controlled, a gPhone spring-based gravimeter shows a quasi-linear drift and can reach a long-term stability at the &#181;Gal level.</p><p>This allows experiments such as the one in the Rochefort Cave Laboratory (Belgium). Thanks to the size of the gPhone and its low facility requirements, a monitoring from inside a cave was possible. Coupled with another gravity monitoring at the surface, it reveals new information on the local hydrology of this karstic site.</p>