Members of the BedrettoLab and the Swiss Seismological Service (SED) at ETH Zurich recently installed a seismic station just 400 m beneath the Pizzo Rotondo. The new station closes an important gap in the seismic background monitoring system of the BedrettoLab. It will improve the hypocentre location estimates of earthquakes in and around the Bedretto experimental volumes.
With this latest addition, the BedrettoLab network consists now of five tunnel and three surface stations allowing to closely observe seismic activities in its surroundings. The new station is the closest surface station to the BedrettoLab; it is ~1.2km above and ~500m to the north-east of the tunnel.
The new station includes a high sensitivity and a strong motion sensor also called accelerometer. Both sensors are part of the standard equipment of seismic stations deployed by the SED. The high sensitivity sensor is capable of recording even very small seismic events (M<2), while the accelerometer is capable of measuring moderate and strong local tremors with great accuracy.
As a novelty, the seismometer has been lowered into a ~70cm deep borehole, drilled directly into the Rotondo granite. This new installation technique can potentially reduce ambient noise levels caused by e.g. wind, melt-water or rain. Because of the low noise levels even very weak seismic signals can be detected and characterised.
The new station was installed as part of the extension of the seismic background monitoring system, motivated by the Fault Activation and Earthquake Rupture project (FEAR). The project aims to investigate how earthquakes start and how they stop by initiating small, non-damaging earthquakes on a natural fault in the BedrettoLab. The FEAR monitoring system should allow to image earthquake rupture processes from unusually short distances, and with unusual detail. November 2022