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21.
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
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Inter-Annual Variability and Decadal Trends in Alpine Spring Phenology: A Multivariate Analysis Approach 总被引：1，自引：0，他引：1
Plant phenological observations are of increasing value as indicators of climate change and variability. We developed a robust
multispecies estimate for Swiss Alpine spring phenology for the period 1965–2002 by applying empirical orthogonal function
(EOF) analysis on a combination of 15 spring phases. The impact of climate parameters such as temperature and precipitation
on the phenological development was investigated using a multivariate statistical model. This multispecies estimate proved
to be a good approach to assess the pattern of spring appearance during the last 40 years. It revealed an earlier onset of
spring in recent years, mainly since 1988 when a clear shift in spring appearance occurred. The mean overall trend of 1.5
days per decade was clearly driven by winter and spring temperatures whereas precipitation showed no significant influence.
The dominant EOF patterns suggested a general climate forcing for the observed inter-annual variability independent of single
plant phases. A more regional phenology signal was found in the second EOF mode, indicating slightly weaker phenological trends
in southern Switzerland as well as in higher altitudes. Both, temperature and precipitation contributed to this pattern significantly.
Analysis of single phases confirmed the pattern of the multispecies estimate. All species showed trends towards earlier appearance
ranging from −1 to −2.8 days per decade and the appearance dates had a very high covariance with temperature. 相似文献
24.
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
25.
Peter Steigenberger Volker Tesmer Manuela Krügel Daniela Thaller Ralf Schmid Sibylle Vey Markus Rothacher 《Journal of Geodesy》2007,81(6-8):503-514
Troposphere parameters estimated from space-geodetic techniques, like the Global Positioning System (GPS) or Very Long Baseline
Interferometry (VLBI), can be used to monitor the atmospheric water vapor content. Although the troposphere can only be monitored
at discrete locations, the distribution of the instruments, at least the GPS antennas, can be assumed to be quasi-global.
Critical in the data analysis are systematic effects within each single technique that significantly degrade the accuracy
and especially the long-term stability of the zenith delay determination. In this paper, consistent time-series of troposphere
zenith delays and gradients from homogeneously reprocessed GPS and VLBI solutions are compared for a time period of 11 years.
The homogeneity of these completely reprocessed time-series is essential to avoid misinterpretations due to individual model
changes. Co-located sites are used to investigate systematic effects and the long-term behavior of the two space-geodetic
techniques. Both techniques show common signals in the troposphere parameters at a very high level of precision. The biases
between the troposphere zenith delays are at the level of a few millimeters. On the other hand, long-term trends significantly
differ for the two techniques, preventing climatological interpretations at present. Tests assume these differences to be
due to mathematical artifacts such as different sampling rates and unmodeled semi-annual signals with varying amplitudes. 相似文献
26.
Mary K. Butwin Melissa A. Pfeffer Sibylle von Löwis Eivind W. N. Støren Eniko Bali Throstur Thorsteinsson 《Sedimentology》2020,67(6):3067-3087
The volcanic origin, primarily basaltic, of most of the surface material in Iceland influences its physical properties and appearance. Size distributions, shape analyses and melting experiments were made for surface material collected in high-erosion dust source areas and fresh volcanic ash deposits to determine whether they differ from one another and from dust from other major dust sources. The major differences found between Icelandic dust and dust from other major dust sources in the world, such as the Sahara, are in the particle shapes, lower density and darker colour. Icelandic dust particles greater than 20 μm retain volcanic morphological properties that are also found in fresh volcanic ash. Dust and fresh volcanic ash particles less than 20 μm are crystalline and blocky in nature, similar to the dust from other global source regions. The finer grained (<20 μm) Icelandic particles will have similar suspension and transport behaviours and be similarly hazardous to health and infrastructure as non-Icelandic dust. The coarser particles (>20 μm) will have different suspension and transport behaviours than other dusts due to the volcanic morphology. Icelandic surface material has between 5% and 30% glassy particles compared to fresh volcanic ash which has more than 50% glassy particles. Glassy particles were observed to melt at a lower temperature than the mineral grains; and, as a result, volcanic ash is found to be more threatening to aircraft engines than the typical dust from Iceland. Icelandic dust was observed to be blocky, or plate-like in the respirable size fraction, suggesting similar health hazards as dust from other regions. 相似文献