Author: György Hetényi

C’est ce qu’une étude sismologique récente suggère, mais le diable se cache dans les détails: tout est relatif! En occurrence, relatif à notre rotation à la surface de la Terre. Donc, pas besoin de s’inquiéter d’imminentes catastrophes. Questions et réponses à ce sujet dans cette émission CQFD de la RTS.

A rare succession of two earthquakes larger than magnitude 7.5 has hit Turkey in just over 9 hours this morning. The first, M7.8 event was along the East Anatolian Fault, the second, M7.5 event occurred on a conjugate fault. Aftershocks continue and the number of casualties is still rising. Further seismological information can be found on KOERI’s website, on IRIS, on USGS, etc. An interview in French is available on heidinews.ch here (PDF).

Mise-à-jour 08.02.: article dans Le Temps sur la non-prédictabilité des séismes ici (PDF), explications sur la chaîne Canal9 ici (de 13’04” à 16’27”).

Mise-à-jour 09.02.: podcast sur la prévision des séismes dans Point J de la RTS ici.

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).

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.

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.

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.

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.

On October 6th 2022, the first hole (DT-1b) of project DIVE has started the drilling operations just outside Ornavasso. Bedrock was encountered within a meter from the surface, as predicted by subsurface geophysical surveys by MUL. Partners from numerous countries gather on site to set the routine workflow in the coming days. Updates can be followed at THIS ICDP weblink.

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.

There are rare events in nature. Today the Liechtenstein parliament was debating the matter of earthquake insurance. Exactly at that time, first a magnitude 2.1, then 32 seconds later a magnitude 3.9 earthquake has shaken the building. The session was temporarily interrupted and the chamber evacuated. (Source: euronews). Here is a video about the event: