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   

Rb/Sr record of fluid-rock interaction in eclogites: The Marun-Keu complex, Polar Urals, Russia     

Johannes Glodny  Håkon Austrheim  Anatolij I Rusin 《Geochimica et cosmochimica acta》2003,67(22):4353-4371

Rb/Sr internal mineral isochrons in the eclogite facies Marun-Keu metamorphic complex, Polar Urals, Russia, date periods of fluid-rock interaction and record the metamorphic reaction history. The Marun-Keu complex consists of Late Proterozoic to Early Ordovician, mostly igneous rocks that experienced a subduction-related, non-pervasive eclogite facies metamorphism, followed by a local decompression-related amphibolite facies overprint, during the Uralian orogeny. Field observations show that metamorphic reactions as well as ductile deformation are controlled by local availability of a free fluid phase. Isotopic data reveals that availability of fluids similarly exerts control on isotope distribution. From a relic gabbro which has never been infiltrated by free fluids, a premetamorphic Rb/Sr age of 467 ± 39 Ma was obtained. Rb/Sr isochron ages for 14 samples of eclogite and amphibolite facies assemblages, sampled from within or close to metamorphic fluid veins, range from 352 ± 5 Ma to 360 ± 3 Ma. A Sm/Nd isochron for a metagranite yields an age of 354 ± 4 Ma. Taken together, the ages for both prograde and retrograde metamorphic assemblages overlap within analytical uncertainty and yield an average value of 355.5 ± 1.4 Ma, indicating that the metamorphic evolution and incipient exhumation of the Marun-Keu complex proceeded rapidly. The results demonstrate that assemblages preserve their Rb/Sr isotopic signatures as long as they remain devoid of free fluids, and that only fluid-rock interaction may cause Sr isotope redistribution. In addition, the data suggest local fluid-rock equilibrium, low fluid-rock ratios with overall fluid deficiency, and limited fluid mobility at depth. However, some fluids must have been mobile on the km-scale since they can be traced into the suprasubduction zone mantle wedge. Metasomatic veins in the Rai-Iz ophiolite yield a Rb/Sr mineral isochron age of 373.1 ± 5.4 Ma. They are interpreted as evidence for suprasubduction zone metasomatism in an oceanic setting, prior to subduction of the East European margin and associated formation of eclogites in the Marun-Keu complex.We propose that Rb/Sr mineral-isochron ages provide hygrochronological rather than thermochronological constraints. They define the cooling history only in combination with zircon and apatite fission track data. The straightforward interpretation of Rb/Sr mineral ages as cooling ages is obsolete.  相似文献   

Comparison of Five Eulerian Air Pollution Forecasting Systems for the Summer of 1999 Using the German Ozone Monitoring Data     

Stefan Tilmes  JØrgen Brandt  Frode FlatØy  Robert Bergström  Johannes Flemming  Joakim Langner  Jesper H. Christensen  Lise M. Frohn  Øystein Hov  Ingo Jacobsen  Eberthard Reimer  Rainer Stern  Jörg Zimmermann 《Journal of Atmospheric Chemistry》2002,42(1):91-121

Eulerian state-of-the-art air pollution forecasting systems on the European scale are operated routinely by several countries in Europe. DWD and FUB, both Germany, NERI, Denmark, NILU, Norway, and SMHI, Sweden, operate some of these systems. To apply such modeling systems, e.g. for regulatory purposes according to new EU directives, an evaluation and comparison of the model systems is fundamental in order to assess their reliability. One step in this direction is presented in this study: The model forecasts from all five systems have been compared to measurements of ground level ozone in Germany. The outstanding point in this investigation is the availability of a huge amount of data – from forecasts by the different model systems and from observations. This allows for a thorough interpretation of the findings and assures the significance of the observed features. Data from more than 300 measurement stations for a 5-month period (May–September 1999) of the German monitoring networks have been used in this comparison. Different spatial and temporal statistical parameters were applied in the evaluation. Generally, it was found that the most comprehensive models gave the best results. However, the less comprehensive and computational cheaper models also produced good results. The extensive comparison made it possible to point out weak points in the different models and to describe the individual model behavior for a full summer period in a climatological sense. The comparison also gave valuable information for an assessment of individual measurement stations and complete monitoring networks in terms of the representativeness of the observation data.  相似文献   

Carbonate diagenesis in Quaternary beachrock of Uyombo,Kenya: Sequences of processes and coexistence of heterogenic products     

Prof. Johannes H. Schroeder 《International Journal of Earth Sciences》1979,68(3):894-919

The calcareous quartz sandstone contains a variety of carbonate cements; these and the biogenic carbonate particles have been preserved and altered in various ways.Several inherited submarine intra-particle cements are followed by a submarine high-Mg calcite palisade cement, then by a meteoric low-Mg calcite blocky cement, and finally by a submarine aragonite spherulitic cement. While the sequence of cementation is clearly recognized, the cement assemblage is considerably diversified by various alterations: The palisade cement may be preserved, impoverished in Mg, dissolved, replaced, or neomorphically altered, while the blocky cement may be partially dissolved. As a result of basal dissolution of cement fringes and subsequent cement precipitation in the new pore space the spatial relationship of cements, for example away from a grainsurface, may no more represent the original sequence of cementation, but pretend a more complex diagenetic history.Common carbonate grains are skeletal particles of red and green calcareous algae, molluscs, foraminifers, echinoids, and corals. They are selectively preserved, micritized, dissolved, replaced, or neomorphosed. Preserved and variously altered particles of a given type coexist in outcrop, sample, and thinsection. Even in individual particles original fabric and several alteration products were found. These observations indicate not only gradual or incomplete alteration, but suggest that various alteration processes compete and that micro-environmental parameters play a decisive role in the competition of processes.Using petrographic, chemical, and circumstantial evidence this case history involving sequential, simultaneous, and/or competetive processes is outlined to help interpret other examples of diagenetically complex shallow carbonates.

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Zusammenfassung Der untersuchte kalkige Quarzsandstein, ein quataerer Strandfels, enthält verschiedene Karbonatzemente. Diese wie auch die vorhandenen biogenen Karbonatpartikel sind in verschiedener Weise erhalten oder diagenetisch verändert worden.Vererbten marinen Intrapartikel-Zementen folgt ein mariner Magnesium-Kalzit Palisaden Zement, diesem ein meteorischer magnesiumarmer Kalzit Blockzement und schließlich ein mariner Aragonit Sphaerulit Zement. Diese Zementabfolge ist deutlich zu erkennen, die Zementvergesellschaftung ist jedoch durch die verschiedenen Veränderungen wesentlich vielfältiger geworden. Der Palisaden Zement kann entweder erhalten, Mgverarmt, aufgelöst und danach möglicherweise neomorph oder nach einem Hohlraumstadium ersetzt worden sein; der Blockzement kann teilweise aufgelöst sein. Infolge der partiellen Auflösung von Zementsäumen an der Basis und der nachfolgenden Zementausfällung in dem so entstandenen Hohlraum repräsentiert die räumliche Folge (z. B. von einem Kornrand in die Interpartikelpore hinein) nicht mehr den zeitlichen Ablauf der Zementation, sondern täuscht eine komplexere diagenetische Geschichte vor.Die Karbonatpartikel stammen vorwiegend von kalkigen Rot- und Grünalgen, Mollusken, Foraminiferen, Echinoiden und Korallen. Sie sind selektiv erhalten, mikritisiert, aufgelöst und dann möglicherweise neomorph oder nach Hohlraumstadium ersetzt. Dabei kommen die verschiedenen Erhaltungs- bzw. Veränderungszustände eines bestimmten Partikels nicht nur in einem Aufschluß, sondern auch in einer Probe bzw. einem Dünnschliff nebeneinander vor. Sogar in einem Einzelpartikel werden verschiedene Zustände nebeneinander beobachtet. Diese Beobachtungen zeigen nicht nur, daß die Veränderungen allmählich vor sich gehen, ihr Ablauf also gestört oder unterbrochen werden kann, sondern auch, daß verschiedene Veränderungsprozesse miteinander konkurrieren und daß das Mikromilieu entscheidend beeinflußt, welcher Prozeß wirksam wird.Mit Hilfe petrographischer und chemischer Daten sowie anderer Indizien werden hier in einer Fallstudie eines sehr jungen Gesteins Abfolgen und Konkurrenz diagenetischer Prozesse gezeigt. Dieser Fall soll Verständnis und Interpretation anderer diagenetisch komplexer Flachwasserkarbonate erleichtern.

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Résumé Le grès calcareux étudié contient une variété de ciments carbonatés; ceux-ci et les particules carbonatées d'origine biogénique ont été préservés ou altérés diagéné tiquement de diverses manières.Divers ciments intra-particulaires sous-marines et hérités sont suivis d'abord par un ciment sous-marin palissadique de calcite fortement magnésienne, ensuite par un «blocky cernent» composé de calcite faiblement magnésienne d'origine météorique, et enfin par un ciment sphérulitique aragonitique d'origine sous-marine. Si la succession des phases de sédimentation peut Être clairement connue, l'assemblage des ciments se diversifie considérablement en raison de diverses altérations: le ciment palissadique peut Être préservé bien qu'appauvri en magnésium, remplacé ou altéré par néomorphose tandis que le blocky cement peut Être partiellement dissout. A la suite de dissolution partielle de franges de ciment et de phases de précipitation subséquentes dans les nouvelles porosités ainsi créées, des relations spatiales entre ciments (par exemple en s'éloignant de la surface d'un grain vers l'espace intergranulaire) ne représentent plus les séquences originelles de cimentation mais indiquent une histoire diagénétique plus complexe.Les grains carbonatés plus communs sont des débris bioclastiques d'algues calcaires rouges et vertes, de mollusques, de foraminifères, d'échinoÏdes et de coraux. Ils peuvent Être préservés sélectivement, micritisés, dissous, remplacés ou néomorphosés. Des particules d'un certain type peuvent Être préservées ou au contraire diversement altérées et coexister à l'échelle de l'affleurement, de l'échantillon ou mÊme de la lame mince. MÊme dans les particules individuelles on peut rencontrer cÔte à cÔte les fabrices originelles et divers produits d'altération. Ces observations illustrent non seulement une altération interviennent concurremment et que les paramètres du micro-milieu jouent un rÔle fondamental dans la compétition des processus.

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Impregnation of organic lake sediments for palaeomagnetic measurements     

Reidar Løvlie  Knut Krzywinski  Johannes Kjøde 《Physics of the Earth and Planetary Interiors》1979,20(1):p22-p24

A procedure for impregnating high water-content sediments for palaeomagnetic measurements is described and applied to an organic lake sediment core. Comparison of results obtained by a standard sub-sampling procedure, and by the impregnation method, demonstrates a significant improvement in the scatter of the palaeomagnetic directions using the latter method.  相似文献   

Melting of plagioclase in the system Ab − An − $${\text{H}}_{\text{2}} {\text{O}}$$ and Qz − Ab − An − $${\text{H}}_{\text{2}} {\text{O}}$$ at P H 2 O =5 kbars,an equilibrium problem     

Johannes  Wilhelm 《Contributions to Mineralogy and Petrology》1978,66(3):295-303

Contributions to Mineralogy and Petrology - Melting experiments were performed in the systems at P H 2 O =5 kbars. The compositions of the plagioclases coexisting with melt or with melt and quartz...  相似文献   

Seismic crustal study of the Oslo Rift     

Johannes Tryti  Markvard A. Sellevoll 《Pure and Applied Geophysics》1977,115(4):1061-1085

A seismic refraction investigation across the southern part of the Oslo Rift has been made, based on quarry blasts at three localities. The study shows a three-layered crust with the followingP-wave velocities: . the upper mantleP-wave celocity, is 8.07 km/s. The velocity-depth relationship for the uppermost crust, obtained by solving the Wiechert-Herglotz integral equation numerically, shows a continuously decreasing velocity gradient in the region of the Oslo Rift which approaches zero at a depth of 9 km, the corresponding increase in theP-wave velocity being from 5.55 km/s to 6.34 km/s. The interface separating the subsurface layer ( =6.60 km/s) from the uppermost layer , interpreted as the Conrad discontinuity, is essentially horizontal in the investigated part of the Oslo Rift at a depth of approximately 15 km. A deep crustal layer with aP-wave velocity of 7.10 km/s appears to be related to the rift, though the top of this layer extends somewhat eastwards beneath the Precambrian rocks from the southern part of the rift at a depth of approximately 20 km. The Moho discontinuity is elevated beneath the Oslo Region compared with the surrounding area. A broad regional gravity high of about 45 mgal is observed along the entire rift zone. It is suggested that this anomaly is caused by the elevation of the sub-Conrad and Moho discontinuities during the rifting processes.  相似文献   

A three-dimensional study of mesoscale model response to radiative forcing     

Martin Beniston  Johannes Schmetz 《Boundary-Layer Meteorology》1985,31(2):149-175

An infrared radiation parameterization has been applied to a detailed three-dimensional mesoscale model in order to determine whether radiative forcing significantly affects mesoscale atmospheric processes. By taking into account water vapor, liquid water, and carbon dioxide absorption, the scheme differentiates between cloud and clear air regions. The parametric model is presented, along with an overview of the associated mesoscale model.Comparisons between a control run in which only a uniform cooling rate of l K day^–1 is specified, and runs with the infrared scheme are made for 12-hr simulations. The major feature of the radiative forcing is seen to be strong cloud-top cooling. This leads to enhanced destabilization of the upper cloud layer, which in turn results in faster growth of clouds (and which extend to higher levels) than in the control experiment. The deeper clouds force a more vigorous secondary circulation, in which thermodynamic feedbacks between clouds and their environment are substantially stronger than in the case with only a constant cooling rate. This confirms findings made in previous studies undertaken in small-scale numerical models. The discussion also focuses upon a simulation in which the cloud-top infrared cooling has been smoothed out over neighboring vertical levels, in order to represent a cloud-top height distribution crudely. The results indicate that although the absolute values of cloud-top cooling are reduced with respect to the unfiltered case, the fact that cooling extends even higher than previously predicted leads to the formation of thicker, more vigorous clouds. These clouds interact more intensely with their environment than in the unfiltered situation, thereby considerably modifying the mesoscale atmosphere.  相似文献   

Sliding-no sliding zone effect and age determination of ice cores     

Johannes Weertman 《Quaternary Research》1976,6(2):203-207

At present the age of ice from ice cores taken at depths where the seasonal isotope fluctuations no longer are measurable is estimated from the Dansgaard-Johnsen-Nye analysis of the longitudinal thinning of ice sheets. A significant error occurs in such an age estimate if ice cores are taken from a hole drilled through ice that has flowed from a region of the ice sheet where ice slides over its bed to a region where it cannot slide over its bed. The Camp Century drill hole is in ice which may have had such a flow history. In the zone where sliding ceases to take place, the horizontal ice velocity decreases in magnitude in the lower part of the ice sheet while it increases in the upper part. The average ice velocity remains unchanged in value. As a consequence the upper part of the ice sheet is stretched and the lower part is compressed as ice moves through the sliding-no sliding transition zone. The upper part is stretched to a strain of the order of $\text{1}\text{2}$ and the lower part is compressed to a strain that is of the order of $\text{?}\text{1}\text{2}$. The age of ice from the Dansgaard-Johnsen-Nye analysis is underestimated; the error in the age is of the order of h/a, where h is the ice thickness and a is the accumulation rate. (Larger errors occur if the theory of Johnsen et al. is used to determine the age of the ice.) An error in age of a similar magnitude exists if ice flows from a region in which sliding does not take place into a region in which it does. The Byrd Station drill hole is in ice which probably has such a flow history. In this situation the age of the ice is overestimated. If the annual isotope fluctuations are detectable the sliding-no sliding zone effect will make it appear that a sudden change in the accumulation rate occurred at the time the ice at the upper surface of the ice sheet passed over this zone.  相似文献   

Metastable melting in the granite system Qz-Or-Ab-An-H2O     

W. Johannes 《Contributions to Mineralogy and Petrology》1980,72(1):73-80

Time studies were performed in the quinary system Qz-Or-Ab-An-H₂O at kbars and T=665 ° and 660 ° C. Starting material was a mixture of quartz, alkali feldspar Or₈₀ and plagioclase An₃₁. The compositions of plagioclases of run products were determined and compared with the plagioclase of stable solidus conditions.The solidus of the granite system was fixed at P _HäO=5 kbars using various plagioclase — and appropriate alkali feldspar — compositions besides quartz in the starting mixture (Fig. 1).The results of time studies (Table 3 and Fig. 3) reveal metastable melting in the granite system Qz-Or-Ab-An-H₂O. Plagioclase melts almost stoichiometrically. The new plagioclase compositions formed during melting of cotectic compositions approach the theoretically expected stable plagioclase compositions only extremely slowly. An extrapolation of the data achieved in run times of 5–1,500 h indicates attainment of equilibrium after 10¹⁴ years. Metastable melting of granitic compositions is not only considered as an experimental problem but also as a rock forming process in nature.  相似文献