The 1356 Basel earthquake: an interdisciplinary revision

Within historical times one of the most damaging events in intra-plate Europe was the 1356 Basel earthquake. Given its significance for assessing regional seismic hazard in central Europe, an interdisciplinary project was launched in 2005 to re-explore this event. Our effort aimed to incorporate techniques from history, seismology, archaeology, paleoseismology and engineering. New and reinterpreted historical data from Basel and its surroundings plus archaeological findings on buildings that survived the event and still exist enabled this macroseismic assessment. Palaeoseismological studies combined with historical evidence provided additional data. For the surrounding areas, archaeology offers sparse information on some castles and churches, sometimes supported by historical records. A contemporary source allows some reconstruction of the stronger fore- and aftershocks. This expanded information base improves our sense of the event's damage and consequences. For the city of Basel, the relatively abundant archaeological data allowed us to assess statistically the macroseismic intensity at IX, although the pattern of damage was scattered. Data points for the expected area of damage around Basel are not distributed regularly. The absence of historical and archaeological findings for southern Germany might be due to archival problems; future investigation may improve this situation. Our results confirm that the Basel earthquake was the most destructive known for central Europe. Intensities up to VIII are found within a radius of about 30 km. Analysing the macroseismic field confirms our former assessment of the event and shows an epicenter located about 10 km south of Basel. The most probable range for the moment magnitude Mw is between 6.7 and 7.

Latest Pliocene to recent thick-skinned tectonics at the Upper Rhine Graben - Jura Mountains junction

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. Deflections of recent river courses around the crests of en-échelon-aligned surface anticlines suggest that the deformation is ongoing at present. Retro-deformation of the folds affecting the base of the Sundgau gravels indicates horizontal displacement rates of about 0.05 mm/a. This corresponds to a minimum strain rate in the order of 2·10−16 s−1, given the maximum time span of 2.9 Ma for this deformation, i.e. the biostratigraphically determined minimum age of the gravels. A change from thin-skinned tectonics, that prevailed during the main phase of Jura folding, to very probably still ongoing thick-skinned tectonics is inferred to have occurred in the Late Pliocene. We speculate that this change might be linked to the incipient inversion of Permo-Carboniferous troughs within the Alpine foreland in general. This inversion in dextrally transpressive or purely compressive mode along a WNW-ESE-trending basement fault, that is part of the Rhine-Bresse Transfer Zone, which in turn was prestructured during the formation of the Permo-Carboniferous troughs, could have triggered the 1356 Basel earthquak

Geomorphic response to neotectonic activity in the Jura Mountains and in the southern Upper Rhine Graben

Present-day tectonic activity at the southern end of the Upper Rhine Graben in central Western Europe is evidenced by significant seismicity, which has been documented over hundreds of years. The hazard that is posed by this activity was violently demonstrated in 1356, when an earthquake with an estimated magnitude of ML≈6.5 caused extensive damage to the area of Basel in north-western Switzerland. A sound understanding of the regional tectonic deformation field is a prerequisite for the accurate assessment of this hazard. However, long-term deformation rates in this region are very low. Together with the presence of a network of fault families of different age and orientation, which results from the complex tectonic evolution of this area in the Neogene, this makes the characterisation of the regional deformation field and the identification of active faults difficult. Nevertheless, for a better comprehension of the active tectonic processes in general, and for the assessment of the seismic hazard in this region in particular, an improved understanding of the regional tectonic evolution in the recent geological past is indispensable. This thesis addresses the recent tectonic history of the Basel area by combining seismological data with an investigation of the geomorphological evidence of tectonic activity. The fact that tectonic activity can be recorded and preserved by the landscape provides an additional source of information that has been little used so far. It offers an opportunity to extend the time-scale of observation from the decades covered by (instrumental) seismologic and geodetic records further into the past. Whereas a wide range of geomorphic features can carry signatures of past tectonic events, the focus in this work is laid on fluvial geomorphology. The fluvial system in the northern Alpine foreland has been affected by a number of large-scale tectonic events since the late Oligocene. Apart from processes related to the Alpine orogeny and the rifting of the Upper Rhine Graben and Bresse Graben, the evolution of the Jura fold-and-thrust belt, the most external element of the Alpine orogen, dramatically influenced the drainage system. Sedimentary and morphological evidence of former river courses allow further constraining the evolution of the drainage system between the Oligocene and the Quaternary. The tectonic history in the Quaternary was studied using a quantitative geomorphological approach. On the basis of a digital elevation model, geomorphic indices (steepness and concavity index) were determined to characterise the longitudinal profile for a large number of rivers in the area of the southern Upper Rhine Graben and the eastern Jura fold-and-thrust belt. The spatial distribution of these indices indicates uplift of a region roughly corresponding to the Jura fold-and-thrust belt, as well as subsidence of the interior parts of the Upper Rhine Graben relative to the Tabular Jura. A morphological analysis of Late Quaternary alluvial terraces in the lower Aare valley, northern Switzerland, was carried out using a high-resolution digital elevation model. The results suggest regional northward tilt during the past 20’000 years, compatible with both a general (isostatic) uplift of the Swiss Molasse basin, and continuing convergence due to ongoing Alpine collision. The geomorphic data revealed no unambiguous evidence of recent tectonic activity on individual faults. Furthermore, no evidence of recent or ongoing thin-skinned deformation in the Mesozoic sedimentary cover could be identified. The study area at the junction of the Upper Rhine Graben and the Jura fold-and-thrust belt is characterised by a pronouncedly diffuse distribution of deformation, typical for regions where strain is accommodated on inherited tectonic structures. The superposition of large-scale regional uplift and small-scale deformation on individual faults, as well as seismic and aseismic movements, results in a distinct heterogeneity of deformation styles in the northern Alpine foreland

The history of historical earthquake research in Germany

The paper summarizes the history of collecting and evaluating information on earthquakes in Germany. A rich literature mentioning historical and contemporary earthquakes has existed since the 16th century. Early earthquake catalogues began to appear in the middle of the 16th century, some of which report earthquakes in Germany dating back to the 9th century. Modern seismological views were introduced in connection with intense philosophical analysis of the 1755 Lisbon earthquake, which was largely observed in Central Europe. The 19th century was characterized by a tremendous increase in detailed earthquake studies as well as earthquake compilations in the form of catalogues. The most comprehensive non-parametric catalogues were created in the middle of the 20th century, while the first digital parametric catalogues were published in the 1980s. This was also the time when critical studies on the re-interpretation of historical earthquakes began. Only in the 1990s was such analysis made in a systematic manner resulting in numerous publications and the current development of a modern earthquake catalogue

Seismotectonics of southeast France: from the Jura mountains to Corsica

The analysis of the seismicity catalog (1996 to 2019) covering the region from the Jura mountains to Corsica provides a first-order image of the distribution of earthquakes, highlighting large structures such as the Briançonnais and Piedmontais seismic arcs, the eastward deepening of the focal depths through the Western Alps, several large active faults (e.g. Belledonne, Middle Durance, Ligure). Over this period the magnitudes are moderate and the focal mechanisms of the main events display a diversity of seismic behaviors that can be explained by the complexity of the different geological domains with a more or less strong structural inheritage, by variable rheological characteristics at the scale of the crust and by the joint action of different mechanisms of deformation. The distribution of the historical events is in fairly good agreement with the instrumental seismicity, but several earthquakes of $M >6$ are highlighted since the 14th century until the beginning of the 20th

Seismotectonics of southeast France: from the Jura mountains to Corsica

The analysis of the seismicity catalog (1996 to 2019) covering the region from the Jura mountains to Corsica provides a first-order image of the distribution of earthquakes, highlighting large structures such as the Briançonnais and Piedmontais seismic arcs, the eastward deepening of the focal depths through the Western Alps, several large active faults (e.g. Belledonne, Middle Durance, Ligure). Over this period the magnitudes are moderate and the focal mechanisms of the main events display a diversity of seismic behaviors that can be explained by the complexity of the different geological domains with a more or less strong structural inheritage, by variable rheological characteristics at the scale of the crust and by the joint action of different mechanisms of deformation. The distribution of the historical events is in fairly good agreement with the instrumental seismicity, but several earthquakes of $M >6$ are highlighted since the 14th century until the beginning of the 20th

Burial condition is the most important factor for mtDNA PCR amplification success in Palaeolithic equid remains from the Alpine foreland

Faunal remains from Palaeolithic sites are important genetic sources to study preglacial and postglacial populations and to investigate the effect of climate change and human impact. Post mortem decay, resulting in fragmented and chemically modified DNA, is a key obstacle in ancient DNA analyses. In the absence of reliable methods to determine the presence of endogenous DNA in sub-fossil samples, temporal and spatial surveys of DNA survival on a regional scale may help to estimate the potential of faunal remains from a given time period and region. We therefore investigated PCR amplification success, PCR performance and post mortem damage in c. 47,000 to c. 12,000-year-old horse remains from 14 Palaeolithic sites along the Swiss Jura Mountains in relation to depositional context, tissue type, storage time and age, potentially influencing DNA preservation. The targeted 75 base pair mitochondrial DNA fragment could be amplified solely from equid remains from caves and not from any of the open dry and (temporary) wetland sites. Whether teeth are better than bones cannot be ultimately decided; however, both storage time after excavation and age significantly affect PCR amplification and performance, albeit not in a linear way. This is best explained by the—inevitable—heterogeneity of the data set. The extent of post mortem damage is not related to any of the potential impact factors. The results encourage comprehensive investigations of Palaeolithic cave sites, even from temperate regions