Southwest Switzerland Research Articles

Geographical Requirements for the Applicability of the Results of the RACECAT Study to Other Stroke Networks.

Background The RACECAT (Transfer to the Closest Local Stroke Center vs Direct Transfer to Endovascular Stroke Center of Acute Stroke Patients With Suspected Large Vessel Occlusion in the Catalan Territory) trial was the first randomized trial addressing the prehospital triage of acute stroke patients based on the distribution of thrombolysis centers and intervention centers in Catalonia, Spain. The study compared the drip-and-ship with the mothership paradigm in regions where a local thrombolysis center can be reached faster than the nearest intervention center (equipoise region). The present study aims to determine the population-based applicability of the results of the RACECAT study to 4 stroke networks with a different degree of clustering of the intervention centers (clustered, dispersed). Methods and Results Stroke networks were compared with regard to transport time saved for thrombolysis (under the drip-and-ship approach) and transport time saved for endovascular therapy (under the mothership approach). Population-based transport times were modeled with a local instance of an openrouteservice server using open data from OpenStreetMap.The fraction of the population in the equipoise region differed substantially between clustered networks (Catalonia, 63.4%; France North, 87.7%) and dispersed networks (Southwest Bavaria, 40.1%; Switzerland, 40.0%). Transport time savings for thrombolysis under the drip-and-ship approach were more marked in clustered networks (Catalonia, 29 minutes; France North, 27 minutes) than in dispersed networks (Southwest Bavaria and Switzerland, both 18 minutes). Conclusions Infrastructure differences between stroke networks may hamper the applicability of the results of the RACECAT study to other stroke networks with a different distribution of intervention centers. Stroke networks should assess the population densities and hospital type/distribution in the temporal domain before applying prehospital triage algorithms to their specific setting.

New insights into the Rhône–Simplon fault system (Swiss Alps) from a consistent earthquake catalogue covering 35 yr

SUMMARYSeismotectonic interpretations in regions characterized by low to moderate seismicity require consistent earthquake catalogues covering periods of several decades. Inevitable changes in network configuration and analysing procedures, however, introduce significant bias to the hypocentre parameters and uncertainty estimates reported in such catalogues. To overcome these limitations, we developed a procedure using coupled hypocentre-velocity inversions to compute consistent hypocentre locations covering time periods of several decades while accounting for changes in network geometry. We apply these procedures to 35 yr of instrumentally recorded seismicity along the Rhône–Simplon fault system in southwest Switzerland, which is at the transition between the Central and Western Alps. The entire catalogue is relocated using a probabilistic location algorithm in combination with the derived minimum 1-D velocity models. A combination of location parameters is used to define consistent location-quality classes allowing for reliable interpretation of epicentres and focal depths. The relocated catalogue is interpreted together with a recent 3-D P-wave tomographic model and available 2-D reflection seismic profiles. The relocated hypocentres indicate that the major band of seismicity north of the Rhône valley is associated with a 30–40 km long, steeply north-dipping shear zone, which roots in the crystalline basement of the Aar Massif and extends to the shallowest levels of the sedimentary cover of the Helvetic nappes in the Rawil Depression. Seismicity towards the southwest indicates the existence of a similar shear zone within the Aiguille Rouge Massif. This zone possibly extends to the northeast and joins the Rawil fault zone. To the south of the Rhône valley, seismicity is scattered within the Penninic nappes, but limited to the hanging wall of the Pennine Basal Thrust (PBT). The Penninic nappes are characterized by a relatively higher VP of about 5 per cent compared to the Aar Massif, indicating differences in composition or metamorphic grade across the PBT.

The fall of the summer truffle: Recurring hot, dry summers result in declining fruitbody production of Tuber aestivum in Central Europe.

Global warming is pushing populations outside their range of physiological tolerance. According to the environmental envelope framework, the most vulnerable populations occur near the climatic edge of their species' distributions. In contrast, populations from the climatic center of the species range should be relatively buffered against climate warming. We tested this latter prediction using a combination of linear mixed effects and machine learning algorithms on an extensive, citizen-scientist generated dataset on the fruitbody productivity of the Burgundy (aka summer) truffle (Tuber aestivum Vittad.), a keystone, ectomycorrhizal tree-symbiont occurring on a wide range of temperate climates. T. aestivum's fruitbody productivity was monitored at 3-week resolution over up to 8 continuous years at 20 sites distributed in the climatic center of its European distribution in southwest Germany and Switzerland. We found that T. aestivum fruitbody production is more sensitive to summer drought than would be expected from the breadth of its species' climatic niche. The monitored populations occurring nearly 5°C colder than the edge of their species' climatic distribution. However, interannual fruitbody productivity (truffle mass year-1 ) fell by a median loss of 22% for every 1°C increase in summer temperature over a site's 30-year mean. Among the most productive monitored populations, the temperature sensitivity was even higher, with single summer temperature anomalies of 3°C sufficient to stop fruitbody production altogether. Interannual truffle productivity was also related to the phenology of host trees, with ~22 g less truffle mass for each 1-day reduction in the length of the tree growing season. Increasing summer drought extremes are therefore likely to reduce fruiting among summer truffle populations throughout Central Europe. Our results suggest that European T. aestivum may be a mosaic of vulnerable populations, sensitive to climate-driven declines at lower thresholds than implied by its species distribution model.

Coincidence of temperature extremes and phenological events of grapevines

A growing number of studies have highlighted the consequences of climate change on agriculture, including the impacts of climate extremes such as drought, heat waves and frost. The aim of this study was to assess the influence of temperature extremes on various phenological events of grapevine varieties in Southwest Switzerland (Leytron, Canton of Valais). We aimed to capture the occurrence of extreme events in specific years in various grapevine varieties and at different phenological phases to rank the varieties based on their sensitivity to temperature extremes and thus quantify their robustness. Phenological observations (1978–2018) of six Vitis vinifera varieties (Arvine, Chardonnay, Chasselas, Gamay, Pinot noir and Syrah) were subjected to event coincidence analysis. Extreme events were defined as values in the uppermost or lowermost percentiles of the timing of the phenophases and daily temperatures within a 30-day window before the phenophase event occurred. Significantly more extreme temperature and phenological events occurred in Leytron between 2003 and 2017 than in the earlier years, with the years 2007, 2011, 2014 and 2017 being remarkable in terms of the number of extreme coincidence events. Moreover, bud development and flowering experienced significantly more extreme coincidence events than other phenophases; however, the occurrence rate of extreme coincidence events was independent of the phenophase. Based on the total number of extreme events, the varieties did not differ in their responses to temperature extremes. Therefore, event coincidence analysis is an appropriate tool to quantify the occurrence of extreme events. The occurrence of extreme temperature events clearly affected the advancement of the timings of phenological events in various grapevines. However, there were no varietal differences in terms of response to extreme temperatures; thus, additional research is warranted to outline the best adaptation measures.

Modelling of landslides in a scree slope induced by groundwater and rainfall

Predicting the trigger of a slope failure of a steep Alpine scree slope in south-west Switzerland is challenging. The groundwater (GW) flow from snow-melting and rainfall infiltration during summer changes the susceptibility to surficial failure, which also depends on the slope angle, bedrock geometry, stratigraphy and the shear strength of the soil. Surficial failure mechanisms are investigated using prototype ground models that integrate input from field monitoring, geological observations and soil properties and account for relevant factors and constraints for physical and numerical modelling. Shallow scree deposits overlying various bedrock configurations (parallel to the slope, with and without a step) were tested under two hydrological regimes: GW flow, and GW combined with additional intense rainfall. Numerical modelling was used to study the parameter combinations that would lead to failure, and worst-case scenarios were defined in terms of the bedrock geometry and hydraulic perturbations. These results were verified using advanced physical modelling techniques in a geotechnical drum centrifuge. Physical modelling results indicated that, for a given GW condition, slope stability decreases (a) as the depth of the soil cover over the bedrock decreases and (b) the higher the bedrock step. Furthermore, a bedrock step impacts the volume and the location of the triggered failure. Rainfall exacerbates the situation.

Modeling the Seismic Response of Unstable Rock Mass With Deep Compliant Fractures

AbstractAn experimental quantification of the strength and volume of real, heterogeneous, fractured rock masses is crucial when assessing rock slope stability. In order to quantitatively characterize the internal structure of fractured rock slopes, we present three‐dimensional numerical simulations of seismic wave propagation and compare with observations. We introduce a simple, effective model for fractured rock mass, which can easily be applied to simulate weak‐motion seismic wave propagation. The macroscopic compliant fractures cutting the rock mass are modeled as finite‐width zones of reduced elastic parameters characterized by shear and normal stiffness. The widths of such zones are not fixed and can be adjusted to fit the grid step in the numerical method. The proposed rock mass model is applied and tested for the Walkerschmatt site in southwest Switzerland. Synthetic ambient vibrations are generated using a finite‐difference method for the fractured rock mass, shaped by the real terrain geometry, and compared with the measurements. The observed seismic response is satisfactorily reproduced in a broad frequency range (0.5–10 Hz). The synthetized response is primarily controlled by the stiffness, depth, number of fractures, and inertial mass of the fractured rock. The simulated amplification and ground‐motion directionality correspond with the observed levels, unless (1) the simplified cracks reach depths of 200–300 m; and (2) the fracture network is larger with respect to the mapped network. This illustrates the potential of ambient vibration methods in combination with numerical simulations to infer depth, volume, and mechanical characteristics of slope instability.

Disentangling human impact from natural controls of sediment dynamics in an Alpine catchment

AbstractHuman activities have increasingly strong impacts on the sediment dynamics of watersheds, directly, for example through water abstraction and sediment extraction, but also indirectly through climate change. This study aims at disentangling these impacts on natural sediment fluxes for the Borgne River, located in the Alps of southwest Switzerland, using two approaches: First, an assessment of contemporary sediment sources and their relative contribution to the sediment delivered to the catchment outlet is undertaken by geochemical fingerprinting and a mixing model. Second, a spatially distributed conceptual model of suspended sediment production and transfer is used to quantify the contribution of different portions of the catchment to the total sediment yield. The model describes the influence of hydroclimatic variables (rainfall, snowmelt, and ice melt), water diversions and reservoir trapping on the sediment yield accounting for the erodibility of the different land covers present in the catchment. The analysis of different scenarios based on this conceptual model aids the interpretation of the fingerprinting results and the identification of the most important factors controlling sediment fluxes. Although the conceptual model overestimates the contribution of the downstream source area and underestimates the contribution of the upstream source area, the results allow us to qualitatively assess the impacts of different drivers influencing the sediment yield at the catchment scale. The results suggest: (1) high sediment yield from the uppermost part of the catchment due to sediment delivery by glacial ice melt; (2) delayed sediment transfer from areas impacted by water abstraction; and (3) reduced sediment contribution from areas upstream of a major hydropower reservoir that intercepts and traps sediment. Although process (1) and processes (2) and (3) serve to counter one another, our study emphasizes that the relative impacts of Anthropocene climate change and human impacts on sediment delivery may be disentangled through multi‐proxy approaches. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.

Population trends of the Peregrine Falcon in Switzerland with special reference to the period 2005–2016

AbstractWe study population trends of the Peregrine Falcon(Falco peregrinus)in Switzerland with special reference to the development since 2005 and three study areas, South West Switzerland (4,993 km2, 1960–2015), the Northern Jura mountains (3,270 km2, 2005–2015) and the Canton of Zurich (1,748 km2, 2002–2015). We used dynamic occupancy models, which allow the territory-specific extinction and colonization parameters – the demographic rates (at the territory level) underlying a population trend – to be estimated. The Swiss peregrine population has developed in line with trends observed in many other countries and regions in North America and Europe: after the pesticide-induced collapse between the 1950s and 1970s, the population largely recovered up to the turn of the millennium. However, in recent years, we detected significant declines again: in SW Switzerland, the population decreased from 51 to 33 pairs during 2008–2015 (-35%), in the N Jura from 70 to 40 pairs during 2009–2015 (-43%) and in Zurich from 6–7 to 2–4 pairs during 2010–2015 (-50%). In the same time, the local extinction rate in the three study areas (more than) doubled from (0.05) 0.1 to 0.2, while the colonization rate dropped from 0.3 to 0.1 in one of the areas, while no change was detectable in the other two. We discuss two factors responsible for these strong, recent declines of Swiss peregrines: (1) predation by Eagle Owls(Bubo bubo)and (2) direct and illegal persecution by humans. In addition to these two factors, growing human disturbance (e.g. through climbers, bird photographers, paragliders, hikers, geocachers, etc.) and fatalities due to collisions with man-made structures (power lines, glass, wind turbines, etc.) are also suspected to contribute to the population decline.

Genetic Variation of European Beech Populations and Their Progeny from Northeast Germany to Southwest Switzerland

Climate change can adversely affect the growth of European beech (Fagus sylvatica L.) across its entire distribution range. Therefore, knowledge of the adaptive potential of this species to changing climatic conditions is of foremost importance. Genetic diversity is the basis for adaptation to environmental stress, and the regeneration phase of forests is a key stage affecting genetic diversity. Nevertheless, little is known about the effect of climate change on the genetic diversity of adult trees compared to their progeny. Here, we present genetic diversity data for 24 beech populations ranging from northeast Germany to southwest Switzerland. Potentially adaptive genetic variation was studied using single nucleotide polymorphism (SNP) markers in candidate genes that are possibly involved in adaptive trait variation. In addition, more than 2000 adult trees and 3000 of their seedlings were genotyped with simple sequence repeat (SSR) markers to determine selectively neutral genetic diversity and differentiation among populations. All populations showed high SSR and SNP variation, and no differences in genetic diversity were found between adult trees and their offspring. The genetic differentiation between adults and seedlings within the same stands was also insignificant or very low. Therefore, we can conclude tentatively that the transfer of genetic variation among tree generations, currently, is not much affected by climate change, at least in the studied beech populations.

Antiretroviral Pre-exposure Prophylaxis Awareness, Experience And Acceptance Among Men Who Have Sex With Men In Southwest Switzerland

Antiretroviral Pre-exposure Prophylaxis Awareness, Experience And Acceptance Among Men Who Have Sex With Men In Southwest Switzerland

Hepatitis C Virus Awareness Among Men Who Have Sex With Men in Southwest Switzerland.

In Switzerland, the incidence of hepatitis C virus (HCV) infection in HIV-positive men who have sex with men (MSM) rose 18-fold between 1998 and 2011. We aimed to evaluate transmission risk factors, awareness, and seroprevalence of HCV among MSM in southwest Switzerland. From 1st June 2011 to 31st August 2012, trained health care professionals invited individuals attending (1) MSM screening clinics and (2) indoor and outdoor meeting areas to complete an anonymous questionnaire. Consenting participants were rapid tested for HCV (OraQuick HCV Rapid Antibody Test). Of 918 MSM approached, 654 agreed to participate, most of whom (536, 82%) were enrolled via MSM screening clinics. Of 654 participants, 21 (3.2%) disclosed being HIV positive; 140 (21%) had unknown HIV status. In the preceding 12 months, 357 (55%) of 654 participants reported unprotected anal intercourse (UAI) and 321 (49%) of 654 participants reported UAI with partners of different/unknown HIV status. Not HIV serosorting was reported more frequently among HIV-positive individuals (76%, P < 0.001). Three hundred two participants (46%) were aware of HCV, awareness being higher among clinic than meeting area participants (49% vs. 33%, P = 0.04). One individual (of 654; 0.2%), with a negative HIV test result 18 months previously was newly diagnosed as being HCV positive on rapid testing. In this sample of predominantly HIV-negative MSM, half the participants were aware of HCV and HCV seroprevalence was low. However, high rates of UAI and of UAI without HIV serosorting were reported. Given the increasing incidence of HCV among HIV-positive men, we propose that HCV counseling should be offered to MSM regardless of HIV status, with testing offered to those at high risk.

An Analysis of the Benefit of Using HEV Genotype 3 Antigens in Detecting Anti-HEV IgG in a European Population

BackgroundThe benefit of using serological assays based on HEV genotype 3 in industrialised settings is unclear. We compared the performance of serological kits based on antigens from different HEV genotypes.MethodsTaking 20 serum samples from patients in southwest France with acute HEV infection (positive PCR for HEV genotype 3) and 550 anonymised samples from blood donors in southwest Switzerland, we tested for anti-HEV IgG using three enzyme immunoassays (EIAs) (MP Diagnostics, Dia.Pro and Fortress) based on genotype 1 and 2 antigens, and one immunodot assay (Mikrogen Diagnostik recomLine HEV IgG/IgM) based on genotype 1 and 3 antigens.ResultsAll acute HEV samples and 124/550 blood donor samples were positive with ≥1 assay. Of PCR-confirmed patient samples, 45%, 65%, 95% and 55% were positive with MP Diagnostics, Dia.Pro, Fortress and recomLine, respectively. Of blood donor samples positive with ≥1 assay, 120/124 (97%), were positive with Fortress, 19/124 (15%) were positive with all EIAs and 51/124 (41%) were positive with recomLine. Of 11/20 patient samples positive with recomLine, stronger reactivity for HEV genotype 3 was observed in 1/11(9%), and equal reactivity for both genotypes in 5/11 (45.5%).ConclusionsAlthough recomLine contains HEV genotype 3, it has lower sensitivity than Fortress in acute HEV infection and fails to identify infection as being due to this genotype in approximately 45% of patients. In our single blood donor population, we observe wide variations in measured seroprevalence, from 4.2% to 21.8%, depending on the assay used.

Population structure and incidence of the stolbur phytoplasma vector Hyalesthes obsoletus (Cixiidae) among geographic regions in Switzerland

AbstractThe dissemination of stolbur phytoplasma (16Sr‐XIIA group)‐induced yellows diseases depends on the dispersal biology and host plant fidelity of the planthopper vector Hyalesthes obsoletus (Hemiptera: Cixiidae). We analysed the degree of these two properties in H. obsoletus by studying its population genetic structure and stolbur infection rates relative to the two major host plants, Convolvolus arvensis and Urtica dioica, in order to infer relevant divisions for stolbur epidemiology in Swiss viticultural regions. Three regional populations with the potential to determine stolbur epidemiology in distinct ways were identified. First, populations associated with U. dioica in northern Switzerland were most related to genetically distinct U. dioica host race populations identified previously in Germany. Second, populations in central and southwest Switzerland were undifferentiated relative to host plant and likely have wider stolbur transmission breadths than the northern specialized populations. Third, populations in south of the Alps (Ticino) were undifferentiated relative to host plant but geographically isolated from other Swiss regions, thus implying separate population dynamics in this area. The knowledge of these three distinct epidemiological cycles will help to adapt management programmes against stolbur diseases in Swiss vineyards.

Suboptimal access to primary healthcare among street-based sex workers in southwest Switzerland

ObjectivesStreet-based sex workers (SSWs) in Lausanne, Switzerland, are poorly characterised. We set out to quantify potential vulnerability factors in this population and to examine SSW healthcare use and unmet healthcare...

Hepatitis E virus seroprevalence among blood donors in southwest Switzerland.

AimThe aim of this study was to determine the seroprevalence of Hepatitis E virus (HEV) among blood donors in southwest Switzerland.BackgroundHEV is recognized as a food-borne disease in industrialized countries, transmitted mainly through pork meat. Cases of transmission through blood transfusion have also been reported. Recent studies have revealed seroprevalence rates of 13.5%, 16.6% and 20.6% among blood donors in England, France and Denmark, respectively.MethodsWe analyzed 550 consecutive blood donor samples collected in the region of Lausanne, canton of Vaud, Switzerland, for the presence of anti-HEV IgG, using the MP Diagnostics HEV ELISA kit. For each donor, we documented age, sex and alanine aminotransferase (ALT) value.ResultsThe study panel was composed of 332 men (60.4%) and 218 women (39.6%). Overall, anti-HEV IgG was found in 27 of 550 samples (4.9%). The seroprevalence was 5.4% (18/332) in men and 4.1% (9/218) in women. The presence of anti-HEV IgG was not correlated with age, gender or ALT values. However, we observed a peak in seroprevalence of 5.3% in individuals aged 51 to 70 years old.ConclusionsCompared with other European countries, HEV seroprevalence among blood donors in southwest Switzerland is low. The low seroprevalence may be explained by the sensitivity of commercial tests used and/or the strict regulation of animal and meat imports. Data regarding HEV prevalence in Swiss livestock are lacking and merit exploration.

HIV-1 Drug Resistance Transmission Networks in Southwest Switzerland

To determine viral subtypes and resistance mutations to antiretroviral treatment (ART) in untreated HIV-1 acutely infected subjects from Southwest Switzerland. Clinical samples were obtained from the HIV primary infection cohort from Lausanne. Briefly, pol gene was amplified by nested PCR and sequenced to generate a 1 kb sequence spanning protease and reverse transcriptase key protein regions. Nucleotide sequences were used to assess viral genotype and ART resistance mutations. Blood specimens and medical information were obtained from 30 patients. Main viral subtypes corresponded to clade B, CRF02_AG, and F1. Resistant mutations to PIs consisted of L10V and accessory mutations 16E and 60E present in all F1 clades. The NNRTI major resistant mutation 103N was detected in all F1 viruses and in other 2 clades. Additionally, we identified F1 sequences from other 6 HIV infected and untreated individuals from Southwest Switzerland, harboring nucleotide motifs and resistance mutations to ART as observed in the F1 strains from the cohort. These data reveal a high transmission rate (16.6%) for NNRTI resistant mutation 103N in a cohort of HIV acute infection. Three of the 5 resistant strains were F1 clades closely related to other F1 isolates from HIV-1 infection untreated patients also coming from Southwest Switzerland. Overall, we provide strong evidence towards an HIV-1 resistant transmission network in Southwest Switzerland. These findings have relevant implications for the local molecular mapping of HIV-1 and future ART surveillance studies in the region.

Development and application of a real-time TaqMan ® qPCR assay for detection and quantification of ‘ Candidatus Mycoplasma haemolamae’ in South American camelids

Two alpacas from a herd in southwest Switzerland died for unknown reasons. Necropsy revealed chronic weight loss and pale mucous membranes. Infection with hemotropic mycoplasmas was suspected and subsequently confirmed by molecular methods. In order to investigate the epidemiological situation in this herd, a real-time TaqMan ® qPCR assay for the specific detection and quantification of hemoplasma infection in South American camelids was developed. This assay was based on the 16S rRNA gene and amplified ‘ Candidatus Mycoplasma haemolamae’ DNA, but not DNA from other hemoplasmas or non-hemotropic mycoplasma species. The lower detection limit was one copy/PCR, and the amplification efficiency was 97.4%. In 11 out of 24 clinically healthy herd mates of the two infected alpacas, ‘ Candidatus M. haemolamae’ infection was confirmed. No correlation was found between bacterial load and clinical signs or anemia. The assay described herein enables to detect and quantify ‘ Candidatus M. haemolamae’ and may be used in future studies to investigate the prevalence, pathogenesis and treatment follow-up of hemoplasma infections in South American camelids.

Stream Temperature Response to Three Riparian Vegetation Scenarios by Use of a Distributed Temperature Validated Model

Elevated in-stream temperature has led to a surge in the occurrence of parasitic intrusion proliferative kidney disease and has resulted in fish kills throughout Switzerland's waterways. Data from distributed temperature sensing (DTS) in-stream measurements for three cloud-free days in August 2007 over a 1260 m stretch of the Boiron de Merges River in southwest Switzerland were used to calibrate and validate a physically based one-dimensional stream temperature model. Stream temperature response to three distinct riparian conditions were then modeled: open, in-stream reeds, and forest cover. Simulation predicted a mean peak stream temperature increase of 0.7 °C if current vegetation was removed, an increase of 0.1 °C if dense reeds covered the entire stream reach, and a decrease of 1.2 °C if a mature riparian forest covered the entire reach. Understanding that full vegetation canopy cover is the optimal riparian management option for limiting stream temperature, in-stream reeds, which require no riparian set-aside and grow very quickly, appear to provide substantial thermal control, potentially useful for land-use management.

The 1946 magnitude 6.1 earthquake in the Valais: site-effects as contributor to the damage

The January 25, 1946 earthquake in the central Valais region in southwest Switzerland was the strongest for the last 150 years. It reached an epicentral intensity Io of VIII in the area of Sierre. The Swiss Earthquake Catalogue (ECOS 2002) assigns a moment magnitude of Mw = 6.1 to the event. Assessment of recordings from European stations resulted in a moment magnitude of 5.8 (Bernardi et al. 2005). The earthquake caused moderate to high damage within a circle of about a 25 kilometer radius. Slight damage occurred up to a distance of 200 kilometers from the epicenter. The goal of this study was to reconstruct the damage field and consider its possible site-effects. We used an approach combining historical research with seismo-/geological investigation including a large number of experiments measuring the fundamental frequency of resonance and the shear-wave velocities of the sedimentary layers, using the characteristics of ambient vibration. This kind of research is relevant, since a huge alpine valley characterizes the Valais region, showing ground conditions that make site-effects likely for earthquakes. While we searched for damage in an unlimited area, our investigation of site-effects was limited to the Rhone valley and to Sion and Sierre in the central Valais region in particular. Since a contemporary damage assessment has survived in fragments only, the results of our historical investigation are incomplete. Nevertheless, it was possible to describe the losses within the epicentral region adequately enough to discuss possible site-effects. Our results show that Valaisan districts with a high percentage of settlement on the lacustrine and fluviatile deposits of the Rhone valley show higher losses than other districts. The villages of Sierre and Sion we investigated in more detail. Sion is located on compacted sediments with relatively high shear-wave velocities. The city suffered only moderate damage, rather regularly distributed. In Sierre, on the other hand, we identified two zones of significantly increased damage, in which site-effects appear a very probable contributor. Local two- or three-dimensional resonance phenomena play an important role in explaining this feature.

Magnetic fabrics of the Morcles Nappe complex

Anisotropy of magnetic susceptibility (AMS) measured with high fields, at ambient and low temperatures (77 K), has been used to separate ferromagnetic ( sensu lato), paramagnetic and diamagnetic sub-fabrics for deformed limestones located in a nappe structure from southwest Switzerland. The magnetic fabrics are dominantly controlled by paramagnetic and diamagnetic minerals, and ferromagnetic minerals contribute significantly only at two of the eight study locations. Separation of the magnetic sub-fabrics is possible in the root zone and overturned limb of the Morcles Nappe, which contains a high ratio of diamagnetic matrix calcite to paramagnetic secondary phases. Each of the sub-fabrics displays a relationship with structural cleavage and the crystallographic preferred orientation (CPO) of calcite in the root zone and overturned limb. The maximum axis of the paramagnetic AMS ellipsoid ( k max) lies close to the pole to cleavage, with the intermediate ( k int) and minimum ( k min) axes near the cleavage plane. Conversely, the diamagnetic k min lies close to the pole to cleavage with k max and k int axes near the cleavage plane. Slight offsets in the poles to cleavage and in the principal AMS directions are observed. They are interpreted to be the consequence of a second phase deformation event, affecting only the CPO but not the macroscopic structural elements. The diamagnetic sub-fabric reflects the CPO of calcite, produced through recrystallization during nappe deformation. Iron-rich calcite appears to control the paramagnetic sub-fabric. Susceptibility ellipsoids approach oblate shapes for the diamagnetic sub-fabric, with the most extreme shapes reaching susceptibility differences (Δ k = k max − k min) close to that of single crystal calcite, whereas the paramagnetic sub-fabric is represented mainly by prolate shape ellipsoids. The low-field AMS ellipsoids show mixed oblate and prolate shapes, without consistency within or between sites. It is evident that, when the magnetic sub-fabrics of the root zone and overturned limb are separated, their individual shapes and distribution of principal directions mirror the developed CPO.