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Seismic source characterization is performed as part of the PEGASOS project for the assessment of the seismic hazard at the 4 sites of the Swiss Nuclear Power Plants. The analysis is performed according to the Level 4 procedures for expert elicitation defined in the guidelines of the US Nuclear Regulatory Committee whereby the quantification of uncertainties plays a crucial role. According to our analysis, which is one amongst four that were performed in the frame of PEGASOS, the most important epistemic uncertainty is related to the question as to weather basement-rooted faults at the margins of pre-existing Permo-Carboniferous troughs are prone for compressive or transpressive reactivation under the present-day stress field or not. The question after the present-day style of deformation in the Alpine foreland (thick-skinned versus thin-skinned) is closely related to this key question. Together with the consideration of uncertainties regarding the mapping of seismogenic zones and/or line sources alternative zonations are presented in form of a logic tree with 21 branches. Area sources play a predominant role in the working area located at the margin of a diffuse plate boundary.

We briefly report on the conference held in May 2007 in honour of Martin Burkhard in Neuchâtel. We also present a short account of the achievements of this prominent scientist and teacher by selectively citing some of his work and briefly introduce the series of articles presented here, which represent a tribute to Martin Burkhard. We also add a complete list of publications by Martin Burkhard and co-workers.

The Cenozoic-age metamorphic structure of the Alps consists of a throughgoing pressure-dominated belt (blueschists and eclogites) that strikes parallel to the orogen and was later truncated by two thermal domes characterised by Barrow-type metamorphism (Lepontine dome and Tauern window). This study documents for the first time that relics of Fe-Mg carpholite occur also within meta-sedimentary units that are part of the north-eastern Lepontine structural and metamorphic dome, where so far exclusively Barrovian assemblages were found. They occur in meta-sediments of both Valais Oceanderived Lower Penninic Bündnerschiefer and structurally lower Europe-derived Sub-Penninic cover nappes and slices. These high-pressure units were subsequently overprinted by a thermal event, as is documented by the growth of new minerals typical for Barrovian metamorphism.

A map-view palinspastic restoration of tectonic units in the Alps, Carpathians and Dinarides reveals the plate tectonic configuration before the onset of Miocene to recent deformations. Estimates of shortening and extension from the entire orogenic system allow for a semi-quantitative restoration of translations and rotations of tectonic units during the last 20 Ma. Our restoration yielded the following results: (1) The Balaton Fault and its eastern extension along the northern margin of the Mid-Hungarian Fault Zone align with the Periadriatic Fault, a geometry that allows for the eastward lateral extrusion of the Alpine-Carpathian-Pannonian (ALCAPA) Mega-Unit. The Mid-Hungarian Fault Zone accommodated simultaneous strike-perpendicular shortening and strike-slip movements, concomitant with strike-parallel extension. (2) The Mid-Hungarian Fault Zone is also the locus of a former plate boundary transforming opposed subduction polarities between Alps (including Western Carpathians) and Dinarides. (3) The ALCAPA Mega-Unit was affected by 290 km extension and fits into an area W of present-day Budapest in its restored position, while the Tisza-Dacia Mega-Unit was affected by up to 180 km extension during its emplacement into the Carpathian embayment. (4) The external Dinarides experienced Neogene shortening of over 200 km in the south, contemporaneous with dextral wrench movements in the internal Dinarides and the easterly adjacent Carpatho-Balkan orogen. (5) N–S convergence between the European and Adriatic plates amounts to some 200 km at a longitude of 14° E, in line with post-20 Ma subduction of Adriatic lithosphere underneath the Eastern Alps, corroborating the discussion of results based on high-resolution teleseismic tomography.

Ansorge Jörg (ETHZ)

A correlation of tectonic units of the Alpine-Carpathian-Dinaridic system of orogens, including the substrate of the Pannonian and Transylvanian basins, is presented in the form of a map. Combined with a series of crustal-scale cross sections this correlation of tectonic units yields a clearer picture of the three-dimensional architecture of this system of orogens that owes its considerable complexity to multiple overprinting of earlier by younger deformations.

The southernmost Upper Rhine Graben and adjacent Jura experienced basement-rooted shortening that occurred after the deposition of the Pliocene fluvial “Sundgau gravels”. Folds affecting the base of these gravels systematically trend NE to ENE. Combined evidence from reflection seismic lines and contour maps of the base-Tertiary and base-Pliocene levels indicates that these folds probably formed by thick-skinned reactivation of both NNE-SSW and WSW-ENE-striking faults. This thick-skinned shortening is NW-SE oriented, i.e. parallel to the maximum horizontal stresses inferred from seismotectonics. NNE-SSW-striking faults (paralleling the Upper Rhine Graben) have been reactivated in sinistral strike-slip mode. However, dextrally transpressive reactivation of the WSW-ENE-trending faults that belong to the Rhine-Bresse Transfer Zone is interpreted to predominate.

Paleomagnetic analyses were carried out on samples from 19 localities within two different mega-tectonic units in Northern Romania: Tisza-Dacia (11 localities) and ALCAPA (8 localities). The samples cover a range of different lithologies: (1) Late Cretaceous red-coloured marl to marly limestone, (2) Eo-Oligocene flysch sediments, and (3) mid-Miocene (Langhian) tuffite (Dej tuff and related sediments). The Late Cretaceous and mid-Miocene specimens carry secondary paleomagnetic signals exhibiting a counter clockwise deflection of the paleo-declinations by some 30°, while the Eo-Oligocene localities indicate an overall clockwise deflected (between some 45° and >90°) paleodeclination with respect to present-day north. Clockwise rotation postdates the age of sedimentation (Lower Oligocene), as well as (at least partially) thrusting of the Pienides onto the Tisza-Dacia mega-tectonic unit, which occurred between 20.5 and 18.5 Ma. Clockwise rotation predates post-12 Ma counter clockwise rotations inferred for the mid-Miocene localities.