ALBERT

Description: The Dead Sea Transform (DST) was formed in the Mid-Cenozoic, about 18 Myr ago, as a result of the breakaway of the Arabian plate from the African plate. Higher resolution information about the sub-Moho structure is still sparse in this region. Here we study seismic discontinuities in the mantle lithosphere in the region of the DST using a modified version of the P- and S-receiver function method. We use open data from permanent and temporary seismic stations. The results are displayed in a number of depth profiles through the study area. The Moho is observed on both sides of the transform at nearly 40 km depth by S-to-p and in P-to-s converted signals. The lithosphere-asthenosphere boundary (LAB) on the eastern side of the DST is observed near 180–200 km depth, which is according to our knowledge the first LAB observation at that depth in this region. This observation could lead to the conclusion that the thickness of the Arabian lithosphere east of the DST is likely cratonic. In addition, we observe in the entire area a negative velocity gradient (NVG) at 60–80 km depth, which was previously interpreted as LAB.

Description: We use seismic waveform data from the AlpArray Seismic Network and three other temporary seismic networks, to perform receiver function (RF) calculations and time-to-depth migration to update the knowledge of the Moho discontinuity beneath the broader European Alps. In particular, we set up a homogeneous processing scheme to compute RFs using the time-domain iterative deconvolution method and apply consistent quality control to yield 112 205 high-quality RFs. We then perform time-to-depth migration in a newly implemented 3D spherical coordinate system using a European-scale reference P and S wave velocity model. This approach, together with the dense data coverage, provide us with a 3D migrated volume, from which we present migrated profiles that reflect the first-order crustal thickness structure. We create a detailed Moho map by manually picking the discontinuity in a set of orthogonal profiles covering the entire area. We make the RF dataset, the software for the entire processing workflow, as well as the Moho map, openly available; these open-access datasets and results will allow other researchers to build on the current study. How to cite. Michailos, K., Hetényi, G., Scarponi, M., Stipčević, J., Bianchi, I., Bonatto, L., Czuba, W., Di Bona, M., Govoni, A., Hannemann, K., Janik, T., Kalmár, D., Kind, R., Link, F., Lucente, F. P., Monna, S., Montuori, C., Mroczek, S., Paul, A., Piromallo, C., Plomerová, J., Rewers, J., Salimbeni, S., Tilmann, F., Środa, P., Vergne, J., and the AlpArray-PACASE Working Group: Moho depths beneath the European Alps: a homogeneously processed map and receiver functions database, Earth Syst. Sci. Data, 15, 2117–2138, https://doi.org/10.5194/essd-15-2117-2023, 2023.

Description: 2023 marks thirty years since the start of GEOFON operations with the first three stations in Papua New Guinea (Port Moresby, PMG), the Czech Republic (Moravsky Beroun, MORC), in Ireland (Dublin, DSB). The GEOFON program started shortly after creation of the GFZ German Research Centre for the Geosciences in 1992 with the aim to promote global seismic monitoring, standardisation and data exchange. The program has evolved over the three decades in synergy with the seismological community through three important milestones: since late 1990s the development and community adoption of the SeedLink protocol enabling global real-time data exchange; in early 2000s, development of the Arclink protocol as key development to interconnect the EIDA federated data archives, only recently superseded by the use of FDSN web services at global scale; 2008 as the first public release of SeisComP, one of the most widely used seismological packages in seismology, a development triggered after the 2004 Aceh-Andaman earthquake and tsunami within the GITEWS project (German Indian Ocean Tsunami Early Warning System). Although GEOFON‘s heritage goes back to the 1990s and further down to 1889 building on the initial findings from Ernst von Rebeur-Paschwitz, the program is capable of leveraging third party funded challenging projects to keep modernising with the community. In this presentation we outline the most important developments of GEOFON through a journey in time over three decades, building links between current activities and vision still influenced by the initial aims which have shaped the current GEOFON mission.

Description: The structure of the lithosphere is reflecting its evolution. The Moho of the European lithosphere has already been studied intensively. This is, however, not yet the case for the lower boundary of the lithosphere, that is the lithosphere–asthenosphere boundary (LAB). We are using S-to-P converted seismic waves to study the structures of the Moho and the LAB beneath Europe including the greater Alpine Area with data from the AlpArray project and the European networks of permanent seismic stations. We use plain waveform stacking of converted waves without deconvolution and compare the results with stacking of deconvolved traces. We also compare Moho depths determinations using S-to-P converted waves with those obtained by other seismic methods. We present more detailed information about negative velocity gradients (NVG) below the Moho. Its lower bound may be interpreted as representing the LAB. We found that the thickness of the European mantle lithosphere is increasing from about 50°N towards the Alps along the entire east–west extension of the Alps. The NVG has also an east dipping component towards the Pannonian Basin and the Bohemian Massif. The Alps and their northern foreland north of about 50°N are surrounded in the east, west and north by a north dipping mantle lithosphere. Along 50°N, where the NVG is reversing its dip direction towards the north, is also the area along which the volcanoes of the European Cenozoic Rift System are located. Our results possibly indicate that the Alpine collision has deformed the entire lithosphere of the Alpine foreland as far north as about 50°N.