Author: György Hetényi

The mantle transition zone (MTZ), located typically between 410 and 660 km depth, is often preventing subducted slabs to directly sink further into the lower mantle. Beneath the orogenic belts of Central Europe, the Alps, the Carpathians and the Dinarides, only partial images of the MTZ were available so far. Now, thanks to the dense and longer term temporary passive seismic arrays such as AlpArray and PACASE, the MTZ beneath the entire region, and the enclosed Pannonian Basin, is imaged in 3D and high resolution. The results show that the slab graveyard at the bottom of the MTZ is continuous across the entire region – further details can be read in our recently published GJI paper (Kalmár et al. 2025).

There is a classical figure to show while teaching on earthquakes, which shows what a given level of magnitude means in terms of energy or other processes. This figure is so popular that it will very likely look familiar to you.

During a recent work to prepare educational material for our programs in Switzerland and Nepal, it turned out that the widespread figure had an inconsistency: the left hand side on earthquakes showed only the energy radiated as seismic waves, while the right hand side on other events showed total energy. This has prompted a number of verification calculations and a major revision of the figure, so that it now compares comparable things, all in terms of total energy. Here it is below, and the short story of the revision can be read here.

A telling example of this update is the size of the largest bomb humans have historically created. In the previous diagram it was wrongly compared to a magitude 8 earthquake, but when correctly comparing total energy it is a magnitude 5.5.

A key paper of project DIVE phase 1 has been recently published. The 578.5 m deep borehole has been fully cored, and numerous downhole logging datasets have been acquired. These provide a very rich, comprehensive overview of the middle portion of the continental lower crust at various spatial scales, and matches well the main lithologies recovered from the borehole. For full details, please read the paper by Li, Caspari, Greenwood et al.: “Integrated Rock Mass Characterization of the Lower Continental Crust Along the ICDP-DIVE 5071_1_B Borehole in the Ivrea-Verbano Zone” published in G-cubed.

Under the coordination of SCNAT, the Swiss science community has updated the respective roadmaps for large research infrastructure. These documents serve as basis for the process leading to the Swiss Roadmap for Research Infrastructures 2027 for the ERI Dsipatch 2029-2032. Further information on the community roadmaps are available HERE, and the Geosciences Roadmap is described HERE (direct access to the PDF).

The past summer has been productive in terms of publications.

Related to project DIVE, active seismic site surveys have been published for all three borehole locations: for holes 5071_1_A and _B in Greenwood et al., and for the planned hole in Val Sesia in Pasiecznik et al., nicely complementing results by Ryberg et al. last year.

On larger scales and passive seismic observations, the construction and operation of a large broadband network is demonstrated in Schlömer et al. for project PACASE in Eastern-Central Europe. One of the first seismic catalogues established from low-cost sensors only has been achieved by Subedi et al. in Nepal; the study is nicely summarized by the RaspberryShake here. Finally, how such observations serve seismotectonic interpretations is illustrated in Uthaman et al. on the area of Sikkim Himalaya; the study is highligted by the Editor at AGU’s Eos here.

In summary, seismology remains essential and the primary tool to investigate the internal structure of the Earth.

From July 10th to 12th scientists of the DIVE project and associated researchers will gather in Romagnano Sesia, in the geological Ivrea-Verbano Zone, for the 2024 Science Workshop of the project. With both boreholes fully cored, and hundreds of samples already with the researchers, this workshop will be the prime venue to discuss first results, present further research steps, coordinate joint interests, and foster sample and data sharing. With 39 participants, 19 presentations, and ample time for discussions, we look forward to a productive meeting. The workshop is co-funded by UNIL’s Interdisciplinary Centre for Mountain Research (CIRM), and well as the International Lithosphere Program (ILP).

It is high time for the first post in Italian! Thanks to Marco Gritti from TV Svizzera, you can read and watch a summary of the recently finished borehole and project DIVE activities here.

After half a year spent in Megolo di Mezzo, the drilling activities at the DT-1A borehole are now completed. The hole has reached a final depth of 909.5 metres, fully cored! A little closing ceremony took place at the end of April (see photo), before borehole logging activites on site, and final core description and sampling party in the core repository (in preparation). A big THANK YOU to everyone who has contributed the successful operations!