OROG3NY

The deformation of the Himalayan orogen is rather well known on geological timescale (millions of years) and modern, instrumentally observed timescales (decades). But how does it behave at intermediate timescales? Constraints to give an answer to this question are now available, and are presented and discussed in our new paper in Geology.

A book trilogy has been published this Summer as a result of a broad collaborative effort by geoscience experts working on the Himalayan mountain belt. The series has been edited by iSTE and co-published by Wiley, under the editorial work of Rodolphe Cattin and Jean-Luc Epard. Over a total of about 900 pages, the readers can read about:

• Geodynamic Setting of the Himalayan Range (weblink iSTE, weblink Wiley)
• Tectonic Units and Structure of the Himalaya (weblink iSTE, weblink Wiley)
• Current Activity of the Himalayan Range (weblink iSTE, weblink Wiley)

In our reviewed opinion paper published in the Diamond Open Access journal Seismica, we underscore Nepal’s high earthquake vulnerability and outline an all-encompassing education policy tailored to its needs, crucial for raising awareness across society. See a tweet, a short video, and the Nepali abstract just below.

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.

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.

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.

Ce matin un bloc rocheux a chuté et roulé près de Martigny, selon l’article du Nouvelliste. La vibration causée par cet événement a été enregistrée par un de nos sismomètres scolaires: selon la forme d’onde ci-dessous, l’événement a eu lieu à 7h01 pendant une minute.

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).