Sismo-à-l’école à Martigny

Une nouvelle station du réseau Sismologie à l’école a été installé jeudi 26 janvier à Martigny. Le sismomètre mesure bien les variations du niveau de bruit entre la présence et l’absence des élèves, et a déjà détecté un premier petit séisme, de magnitude 1.4, qui a eu lieu samedi 28 janvier le matin, proche de la triple frontière Suisse-France-Italie. Cette nouvelle installation s’inscrit dans le cadre d’un Travail de Bachelor à l’Université de Lausanne (“Baccalauréat en géosciences et environnement“, orientation Géologie).

Enregistrement du vitesse du sol causé par le séisme à 20 km du sismomètre

DIVE DT-1b completed at 578.7 m depth

The first project DIVE borehole, located in Ornavasso, is now fully drilled, and reached 578.7 m depth below surface. All logging activities are completed for 2022. Both the core and the logging data recovery were very good. For a lookback at the past months activities, this page collects daily news and photos. The borehole is now sealed, as shown on the picture below, and preparation for the second borehole is ongoing.

Gotthard Base Tunnel gravimetric study published

With gravity measurements in the tunnel and on the surface along the tunnel, our study assessed the geological model of the Gotthard Base Tunnel, the currently longest tunnel in the world (57.1 km). It turns out that local and regional rock-density data explain the structure very well. Full details in our publication in Swiss Journal of Geosciences.

The locations of our new surface gravity measurement points along the track of the Gotthard Base Tunnel (view from South).

3-D seismological inversion method for crustal structure published

Following years of development, testing and validation, our new approach how to construct a crustal structure and shear-wave velocity model based on seismic receiver functions has just been published. The first part of the paper explains the methodology, the second applies it to the Central Alps and the AlpArray dataset. One key element is the new model parameterization, shown below.

The new model parametrization: layer boundaries are flexible in depth, velocities are defined twice at each discontinuity (below and above) allowing velocity jumps and also velocity gradients across layers.

DIVE DT-1b at 175 metres

Three weeks into the drilling phase of DT-1b, the hole’s current bottom is at 175 m below surface. There have been smooth and efficient days with night shifts, other days with more or less improvisation, rig change, minor fracture zone, and other adventures. The weekly shifts rotate and we look forward to a first logging session in the coming weeks.

Night-shift motivation and a promising core

Widely felt earthquake near Basel

On Saturday 10.09.2022 a magnitude 4.7 earthquake happened 15 km from Basel, towards Mulhouse (France). The shaking has been widely felt in Switzerland, all across the plateau, and in a large part of the Alps. So far there are no news of damages. A summary in German and French is available on the news page of the Swiss Seismological Service, and the RTS Téléjournal has reported on the event on Sunday. The closest low-cost seismometer of the school seismology network has recorded the following waveform in Bienne/Biel, and here is a figure showing all recordings at schools.