The tip of the mantle-berg

The Balmuccia peridotite body in the Ivrea-Verbano Zone has been interpreted by geologists as a lense: an elongated outcrop of mantle rocks that is disconnected from the real mantle and brough to the surface by tectonics. Geophysical studies in the past have already stipulated that dense and seismically fast rocks, similar to the mantle, must be located at very shallow depth beneath the area (see Scarponi et al. 2020, 2021 for recent, larger scale studies). The most recent result on this question, based on targeted, active source seismic investigation, shows that the connection between the surface and the subsurface exists: the Balmuccia peridotite is the tip of the mantle-berg! For details, please read Ryberg et al. 2023 in GJI.

Figure 7a of Ryberg et al. 2023

Moho depth beneath the European Alps

The thickness of the crust is a key structural parameter in many studies, from geodynamics to surface processes. Following a multi-year effort, and based on the several seismic networks (AlpArray, PACASE, EASI, CIFALPS-I), our publication on the crustal thickness of a large area, encompassing the entire Alps and many of its adjacent regions, has just been published. It is more that a mere map, it also presents numerous cross-sections, and openly shares the raw and processed seismological data (receiver functions) for future users. For full details, see Michailos et al. (2023) in ESSD.

3rd Educational Seismology workshop in Nepal

Today is the 8th anniversary of the devastating 2015 Gorkha earthquake. Our educational seismology program, Seismo at School in Nepal, has held its first workshop in 2019, followed by several other, smaller activities during times of the pandemic restrictions. This year we are happy to be back with a full program and an in-person workshop in Pokhara, between May 1st and 3rd. Many thanks to the sponsors: EGU, IUGG and UNIL.

Devastating M7.5+ earthquakes in Turkey

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 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.

Screenshot from KOERI’s website on 2023.02.06 at 20:10 UTC showing the earthquake events until then

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).