Earthquakes in Switzerland and surrounding regions during 2010     

Nicholas Deichmann  John Clinton  Stephan Husen  Benjamin Edwards  Florian Haslinger  Donat Fäh  Domenico Giardini  Philipp Kästli  Urs Kradolfer  Stefan Wiemer 《Swiss Journal of Geoscience》2011,104(3):537-547

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2010. During this period, 407 earthquakes and 85 quarry blasts were detected and located in the region under consideration. With a total of only 19 events with M_L ≥ 2.5, the seismic activity in the year 2010 was below the average over the previous 35 years. The two most noteworthy earthquakes were the M_L 3.4 Barrhorn event near Sankt Niklaus (VS) and the M_L 3.0 event of Feldkirch, both of which produced shaking of intensity IV.  相似文献   

A theory for the solar type-I radio continuum     

Donat G. Wentzel 《Solar physics》1986,103(1):141-151

The type-I radio continuum may arise from the combination of two electrostatic waves, both directed nearly normal to the magnetic field. One wave, near the upper-hybrid frequency, is generated by gyroresonance with superthermal electrons and comes into equilibrium with these electrons. The other wave, at the lower-hybrid frequency, is generated by the loss-cone instability of trapped superthermal protons in those wave directions for which the lower-hybrid frequency is an exact multiple of the proton gyrofrequency. The brightness temperature of the continuum indicates both the energy of the superthermal electrons and the existance of at least a small number of superthermal protons.  相似文献   

A theoretical investigation of average H/V ratios   总被引：9，自引：1，他引：9  

Donat Fäh  Fortunat Kind  Domenico Giardini 《Geophysical Journal International》2001,145(2):535-549

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Freshwater Phytoplankton Bloom in Visovac Lake - A Possible Cause of Benthic Mortality in Krka Estuary (Adriatic Sea, Croatia)     

Donat  Petricioli  Tatjana  Bakran-Petricioli  Damir  Vili&#;i&#; Antonieta  Po&#;ar-Domac 《Marine Ecology》1996,17(1-3):373-382

Abstract. In late summer and early autumn of 1989 benthic mortality in the upper part of Krka estuary extended from the Skradinski buk waterfalls to approximately 5 km downstream. Dead benthic organisms were found on the bottom at depths of up to 4.5 m. During August, a freshwater phytoplankton bloom was recorded in Visovac lake (which supplies the Skradinski buk waterfalls). The green tide in the lake was composed of up to 11.9 million cells. 1^--¹, predominantly of Synedra acus and Dinobtyon sertularia . At that time the maximal total inflow of phytoplankton cells through the waterfalls was approx. 0.41 S^-I (38000 1. d^-1). Cells of these two species died after reaching the salt wedge and the cummulative effect of their decomposition apparently caused an oxygen demand sufficient enough to trigger the benthic mortality. Due to the water mass dynamics, the spreading of mortality downstream was slow (from August to October, approx. 5 km). Certain benthic fishes (like Gobius sp.) were observed on the bottom of the affected area in mid-October 1989.  相似文献   

The earthquake of 250 a.d. in Augusta Raurica, A real event with a 3D site-effect?     

Donat Fäh  Sibylle Steimen  Ivo Oprsal  Johannes Ripperger  Jochen Wössner  Regula Schatzmann  Philipp Kästli  Ina Spottke  Peter Huggenberger 《Journal of Seismology》2006,10(4):459-477

The Roman city Augusta Raurica is located East of Basel, Switzerland. One important topic of the city’s history concerns the hypothesis of an earthquake striking the city in the middle of the third century a.d. This idea had been formulated according to archaeological features and findings, but had not been tested so far. A selection of the archaeological features were reviewed and dated in order to test the hypothesis of a single event. However, archaeological investigations do not draw a conclusive picture; it could not be proven that all features of possible destruction date to the same event. Detailed seismological investigations were performed. These included geological and geotechnical mapping of the unconsolidated sediments. Important parameters such as the thickness and composition of the unconsolidated sediments, the terrain topography and the topography of the bedrock surface were mapped. Ambient vibration H/V measurements provided the fundamental frequency of resonance for the unconsolidated sediments. The velocity of shear waves traveling through sediments is the controlling parameter for amplification of seismic waves. This material property is estimated using the relation between the ellipticity of the fundamental mode Rayleigh wave and the H/V curve. From all information we compiled a three-dimensional model of the surface geology. This model is used to simulate earthquake ground motion and amplification effects in the city, and to map the variability of the amplification. In the part of the city where possible earthquake damage was recognized, amplification occurs in the frequency band of building resonance (2–8 Hz). In the other part of the city amplification occurs much above the building’s resonance. From 1D modelling we estimate a difference in spectral amplification of about a factor of 2.5 to 3 between the two parts of the city. This corresponds approximately to a difference in macroseismic intensity of one unit. 3D modelling showed a large variability of ground motion within very close distance in the part of the city where possible earthquake damage was recognized. The maximum amplification reaches values up to a factor of nine, which is due to 3D effects and the choice of using vertically incident waves. Finally, all paleoseismological findings in the area of Basel were reviewed in order to find indications of a large event in the time-period of interest. Paleoseismological findings provide no hints to a large earthquake in the third century. If we assume that an earthquake caused at least part of the identified damage in Augusta Raurica, we have to assign to this event a magnitude Mw of about 6.0 or even lower, that is much smaller than the value of 6.9 that is actually in the Swiss earthquake catalogue. The earthquake source of this event must then be very close to the site of Augusta Raurica and a strong site-effect occurred in one part of the city.  相似文献   

3D Hybrid Ray-FD and DWN-FD Seismic Modeling for Simple Models Containing Complex Local Structures     

Ivo  Opršal  Johana  Brokešová  Donat  Fäh  Domenico  Giardini 《Studia Geophysica et Geodaetica》2002,46(4):711-730

Hybrid approaches find broad applications wherever all-in-one modelling of source, path, and site effects is too expensive. Our new 3D hybrid approach allows to compute the seismic wavefield in elastic isotropic models containing a complex local structure embedded in a large, but considerably simpler, regional structure. The hybrid modelling is realized in two successive steps.In the 1^st step, the ray or discrete wave number (DWN) method is used to compute the seismic wavefield due to the source and simple regional structure. The complex local structure is not present. Thus, the excitation contains the source and regional path effects. The time history of this wavefield (excitation), recorded at the points of so called excitation box, is stored on a disk. The excitation box envelopes a small portion of a computational domain.The 2^nd step of the hybrid method, now containing the complex local structure, is computed by finite differences (FD) inside the excitation box and its close vicinity. The excitation from the 1^st step is now used to inject the 1^st step wavefield into the 2^nd step computation. After that, the hybrid combination of the 1^st and 2^nd steps contains the source, regional path, and local structure effects at reasonably lower computational costs than in case of all-in-one modelling.The 3D ray-FD method is tested on models in which the locally complex structure is the well-known Volvi lake basin, embedded in various 1D structures. The wavefield is excited by the point source situated outside the basin. Although the structure outside the excitation box may be less dimensional (2D, 1D, homogeneous), the whole problem is actually 3D due to the 3D features of the structure inside the excitation box, 3D shape of the excitation box, and arbitrary source — excitation-box configuration. Simple (1D) structures outside the excitation box allow for comparison with the alternative hybrid DWN-FD results. However the ray method is suitable for computation of 3D regional structures outside the excitation box. The results from both approaches show a very good agreement for realistic crustal and local structural models.  相似文献   

Simulated Ground Deposition Of Fine Airborne Particles In An Array Of Idealized Tree Crowns     

J. Donat  B. Ruck 《Boundary-Layer Meteorology》1999,93(3):469-492

Wind-tunnel experiments were used to investigate the ground deposition of fine airborne particles in an array of idealized tree crowns. The particle ground deposition was modelled with a gaseous tracer instead of solid particles, which is an approach for very fine particles. A chemical method based on the reaction of ammonia and manganese chloride was used to quantify the mass transfer from the simulated atmospheric boundary-layer flow to the surface. Using a tracer gas instead of solid particles can be considered only if turbulent diffusion is the decisive deposition mechanism and effects of sedimentation, impaction, interception or molecular diffusion can be approximately ignored. These constraints are necessary due to scaling problems concerning particle modelling in the small-scale experiment. The intention was to determine the obstacle arrangement density in which the mean ground deposition is maximized for a defined crown form. A deposition amplification factor was defined as the quotient of deposition efficiencies for an area with tree crowns and an open ground with identical similarity parameters. Based on this calculation an increase of the ground deposition by up to 60% should be realistic through a favourable arrangement of tree crowns and tree number density. An increase in turbulence intensity in the flow leads to a significant amplification of the mean ground deposition.  相似文献   

Impact of fish farming on foraminiferal community, Drvenik Veliki Island, Adriatic Sea, Croatia     

Jelena Vidovi&#x;  Vlasta &#x;osovi&#x;  Mladen Jura i&#x;  Donat Petricioli 《Marine pollution bulletin》2009,58(9):1297-1309

This study examined the impact of fish farming on foraminiferal communities in the Adriatic coastal zone. Samples were taken directly beneath the farm, near the edge of the farm, and at a reference station away from the farm. The foraminiferal community near the farm is characterized by Epistominella exigua, Globocassidulina subglobosa, Haynesina germanica and the genera Elphidium, Bulimina and Brizalina. These foraminiferal species are less abundant seaward. Asterigerinata mamilla, Neoconorbina terquemi and genus Cibicides are almost absent below the cages. Total phosphorus (TP) and total nitrogen (TN) in the sediments decrease with distance from the cages. The abundances of E. exigua, G. subglobosa, H. germanica and the genera Elphidium, Bulimina and Brizalina are correlated with TP and TN, indicating their dependence on nutrient input. The absence of A. mamilla, N. terquemi and the genus Cibicides below the cages is a due to a degraded Posidonia community. According to our study, foraminiferal community composition can be used as indicator of organic enrichment caused by fish farm activities.  相似文献   

Probabilistic seismic hazard assessment of Switzerland: best estimates and uncertainties     

Stefan Wiemer  Domenico Giardini  Donat Fäh  Nicholas Deichmann  Souad Sellami 《Journal of Seismology》2009,13(4):449-478

We present the results of a new genera tion of probabilistic seismic hazard assessment for Switzerland. This study replaces the previous intensity-based generation of national hazard maps of 1978. Based on a revised moment-magnitude earthquake catalog for Switzerland and the surrounding regions, covering the period 1300–2003, sets of recurrence parameters (a and b values, M _max ) are estimated. Information on active faulting in Switzerland is too sparse to be used as source model. We develop instead two models of areal sources. The first oriented towards capturing historical and instrumental seismicity, the second guided largely by tectonic principles and express ing the alterative view that seismicity is less stationary and thus future activity may occur in previously quiet regions. To estimate three alterna tive a and b value sets and their relative weighting, we introduce a novel approach based on the modified Akaike information criterion, which allows us to decide when the data in a zone deserves to be fitted with a zone-specific b value. From these input parameters, we simulate synthetic earthquake catalogs of one-million-year duration down to magnitude 4.0, which also reflect the difference in depth distribution between the Alpine Foreland and the Alps. Using a specific predictive spectral ground motion model for Switzerland, we estimate expected ground motions in units of the 5% damped acceleration response spectrum at frequencies of 0.5–10 Hz for all of Switzerland, referenced to rock sites with an estimated shear wave velocity of 1,500 m/s² in the upper 30 m. The highest hazard is found in the Wallis, in the Basel region, in Graubünden and along the Alpine front, with maximum spectral accelerations at 5 Hz frequency reaching 150 cm/s² for a return period of 475 years and 720 cm/s² for 10,000 years. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.  相似文献   

Reliability of Building Inventories in Seismic Prone Regions   总被引：1，自引：0，他引：1  

Sibylle?SteimenEmail author  Donat?F?h  Domenico?Giardini  Martin?Bertogg  Silvio?Tschudi 《Bulletin of Earthquake Engineering》2004,2(3):361-388

A study on uncertainties in building inventory and vulnerability assessment for the city of Basel, Switzerland a moderate hazard but high-risk area is presented. Emphasis is put on the special conditions and demands on the data assessment procedure in such an environment. The building information was assessed from the sidewalk using a method similar to that proposed in FEMA-154. With only three persons working for two weeks, about 10% of the citys building stock was assessed. The quality of the dataset was tested by using pre-existing reference data. These tests revealed patterns of misinterpreted structural information; important features like the floor type in URM buildings were difficult to identify.Six methods are proposed to derive building vulnerability from the collected structural information using the definitions of EMS98. The variation between the individual results was investigated in detail. A sample earthquake scenario with intensity IX in the city of Basel is used to demonstrate the influence of uncertainty in the inventory on the scenario results. The range of variation in the results is huge. Overall damage in the six scenarios differed by up to 27%. The amount of collapsed buildings in the historical part of the city comprised between 28% in the worst case and 3% in the best. There is a distinct influence of the inspectors opinion visible in the scenario results, which introduces a remarkable uncertainty. This emphasizes the importance of reliable inventory assessments and makes uncertainty analysis in earthquake scenarios indispensable – especially in areas of moderate seismicity where observational data from earthquake damage is missing.  相似文献