Ergebnisse der Registrierungen der Zahl der Kondensationskerne in Basel und seiner nächsten Umgebung

Zusammenfassung In Fortsetzung früher mitgeteilter Ergebnisse von Registrierungen mit demVerzár'schen Kernzähler in Basel wird der Einfluss der Luftmassenwechsel, des Sonnenscheins und der Niederschläge auf den Kerngehalt untersucht. Weiterhin werden die Ergebnisse gleichzeitiger Registrierungen im Stadtinnern und am Stadtrand, sowie am Stadtrand und einem Villenvorort eingehend diskutiert.Ein weiterer Vergleich zwischen Basel und Payerne ergibt Beziehungen zwischen den Tagesmitteln der Kernzahlen dieser fast 100 Km von einander entfernten Orte.

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Summary Continuing previously communicated results of recordings with theVerzár nuclei counter at Basle the influences of changes of air masses, of sunshine and precipitation on nuclei concentration are studied. Furthermore the results of simultaneous recordings in the centre of the city and on the outskirts, as well as on the out-skirts of the city and at a near-by village are thoroughly discussed. A further comparison between Basle and Payerne shows connections between daily means of nuclei concentration of these two towns, which are about 100 Km apart.

     

Die Bestimmung einer beliebig gekrümmten Schichtgrenze aus seismischen Reflexionsmessungen

Zusammenfassung Es wird dargelegt wie man eine beliebig gekrümmte Schichtgrenze aus seismischen Reflexionsmessungen längs einer beliebig gekrümmten Messfläche berechnen kann. Dazu wird vorausgesetzt, dass die Flächez=f(x,y), die die Schichtgrenze darstellt und die Messflächez=(x,y) zusammen eine glatte geschlossene Fläche bilden und, dass das eingeschlossene Material homogen und isotrop ist.

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Summary Under the assumption that the measuring surfacez=(x,y) and the reflection horizon of a structurez=f(x,y) have an arbitrary curvature a simple method is developed for calculating the surfacef from seismic reflection data measured along the surface . In addition the general solution is discussed and some special cases are treated.

     

Ein Beitrag zur jungen Bruchtektonik der argentinischen Puna und ihr Verhältnis zu den angrenzenden Andenabschnitten

In an area of the Puna, situated between the parallels of latitude 23° 30′ and 24° south and the circles of longitude 67° 12′ and 66° 45′ west, two groups of slightly diverging reversed and thrust faults of different age have been observed: 1. north-northeast to north striking, pre-Pliocene — Pliocene (?) and 2. north-northwest to north striking, post-Pliocene — Pleistocene (?). In the two groups some reversed faults dip to the west, others dip to the east, forming in between narrow but elongated blocks limited by faults dipping in opposite directions. The depressed blocks, widening downward are called “Furchen” (furrows), the uplifted blocks, narrowing downward are called “Keile” (wedges). Acid intrusions and small effusive basalts are connected with the reversed faults. These structures are very common in the western part of the Andes in northwestern Argentine. The reversed faults and thrusts originated the morphological uplift of the central and eastern Andes.     

Scenarios of Seismic Risk in the United Arab Emirates,an Approximate Estimate

We estimate the losses due to 10 scenario earthquakes in 150 settlements of the United Arab Emirates (UAE). For southern Iran, we use four source zones and the maximum magnitudes in them as determined by GSHAP (7.2 M 8.1). For six local scenario earthquakes, we use the range 5.5 M 6.5, place the sources mainly on mapped faults and vary the distance to major cities from 10 to 60 km. In the test case of the Masafi earthquake (M5, 11 March 2002), the method and data bank we use yield the correct results, suggesting that our approach to the problem is valid for the UAE. The sources in Iran are expected to cause only minor damage, except for an M8.1 earthquake in the Makran region. For such an event we expect some deaths, several hundred injured and a loss of 3–6% of the value to the building stock in the northeastern UAE, including Oman. The losses for local scenarios with epicenters in the unpopulated areas of the UAE and for scenarios with M < 5.8 are estimated to be minor. Because the two major mapped faults run through several of the large cities, scenarios with short epicentral distances from cities have to be considered. Scenarios with M6 near cities lead to estimates of about 1000 ± 500 deaths, and several thousand injured. Most buildings are expected to be damaged to a moderate degree and the loss to buildings is estimated around 1/4of their value. If the magnitude should reach 6.5, the losses to humans and to building value could be staggering. These estimates are approximate because: (1) there exists no local seismograph network that could map active faults by locating microseismicity; (2) there exist no historically old buildings that could serve as tests for effects due to strong ground motion in the past; (3) there exist no microzonation of the subsurface properties in this region of unconsolidated building ground; (4) there exist no detailed inventory of building fragility. Nevertheless, our conclusion that there exists a substantial seismic risk in the UAE is reliable, because our method yields accurate results in the cases of earthquakes with known losses during the last several decades in the Middle East.     

A rocking multianvil: elimination of chemical segregation in fluid-saturated high-pressure experiments

Fluid saturated high-pressure experiments often result in strongly zoned experimental charges, this hinders experimentation in chemically homogeneous systems which in turn has serious consequences on equilibration, reaction progress, and (apparent) phase stabilities. In order to overcome these problems, a 600-ton press accommodating either a multianvil or end-loaded piston cylinder module has been mounted in such a way that it can be turned by 180°, thus inverting its position in the gravity field. During turning, hydraulic pressure, heating power, and cooling water remain connected allowing fully controlled pressures and temperatures during experiments.A series of experiments at 13 GPa, 950°C, on a serpentine bulk composition in the MgO-SiO₂-H₂O system demonstrates that continuous turning at a rate of 2 turns/min results in a nearly homogeneous charge composed of phase E + enstatite. The same experiment at static conditions resulted in four mineral zones: quench phase E, enstatite, enstatite + phase E, and phase E + phase A. Phase A disappears in experiments at a turning rate ≥1 turn/min. A static 15-min experiment shows that zonation already forms within this short time span. Placing two short capsules within a single static experiment reveals that the fluid migrates to the hot spot in each capsule and is not gravitationally driven toward the top. The zonation pattern follows isotherms within the capsule, and the degree of zonation increases with temperature gradient (measured as 10 °C within a capsule) and run time.Our preferred interpretation is that Soret diffusion causes a density-stratified fluid within the capsule that does not convect in a static experiment and results in temperature dependant chemical zonation. The aggravation of zonation and appearance of additional phases with run time can be explained with a dissolution-reprecipitation process where the cold spot of the capsule is relatively MgO enriched and the hot spot relatively SiO₂ and H₂O enriched (at 13 GPa and 950°C). Rocking and tilting of a stratified fluid induces Rayleigh-Taylor instabilities, causing chemical rehomogenization. If turning is faster than the time required to build significant chemical potential gradients in the fluid, chemical zonation in the distribution of the solids is suppressed.     

Verification of our previous definition of preferred earthquake nucleation areas in Kanto-Tokai, Japan

We have proposed that points of future initiation of rupture may be mapped, based on minima in local recurrence times, which are equivalent to local maxima in the probability for main shocks to occur. These minima are often controlled by anomalously low b-values (logN = a − bM). Of the Kanto-Tokai area, approximately 12% showed anomalously short recurrence times and was proposed as asperities, based on seismicity up to 1999. During the period 1999–2003.5, about 75% of the earthquakes with M ≥ 3.5 fell into the asperities, earlier defined (for example 19 out of 23 M ≥ 3.8 events). The probability for this to occur by chance is approximately 2 10^− 14. This supports our idea that the most likely volumes to produce main shocks may be mapped by minima in local recurrence times.     

Global and local controls influencing the deposition of the La Luna Formation (Cenomanian-Campanian), western Venezuela

Bulk and molecular geochemical, micropalaeontological, and carbon-isotopic data are used to address the different local and global factors influencing the environment of sedimentation of the La Luna Formation (Cenomanian-Campanian, approximate palaeolatitude 15°N) in a single section in western Venezuela. Based on the constructed chronostratigraphic framework, oxygen-depleted bottom-water conditions and black-shale deposition started in western Venezuela well before the widespread occurrence of organic-rich sediments in higher palaeolatitude regions such as the Tethys and the North Atlantic near or at the Cenomanian-Turonian boundary. In the La Luna Formation, palaeoenvironmental conditions that allowed the preservation of organic matter (mainly of marine origin), prevailed until Santonian times in a distal platform facies with very low siliciclastic input. Changes in lithology appear to reflect the local response to eustatic sea-level variations and the presence of a migrating upwelling belt affecting the bioproductivity of silica and carbonate. A marked δ¹³C_org isotopic excursion is recognised in the middle part of the section, and is apparently unrelated to local palaeoenvironmental changes in bioproductivity and oxygen depletion. Biological marker data show no variations in association with the isotopic excursion, being mainly controlled by local fluctuations in organic-matter input and preservation.     

The pressure and temperature dependence of the elastic properties of single-crystal fayalite Fe2SiO4

The nine adiabatic elastic stiffness constants of synthetic single-crystal fayalite, Fe₂SiO₄, were measured as functions of pressure (range, 0 to 1.0 GPa) and temperature (range, 0 to 40° C) using the pulse superposition ultrasonic method. Summary calculated results for a dense fayalite polycrystalline aggregate, based on the HS average of our single-crystal data, are as follows: V_p = 6.67 km/s; V_s = 3.39km/s; K= 127.9 GPa; μ = 50.3 GPa; (?K/?P)_T = 5.2; (?μ/?P)_T=1.5;(?K/?T)_P= ?0.030 GPa/K;and,(?/?T)_P =-0.013 GPa/K (the pressure and temperature data are referred to 25° C and 1 atm, respectively). Accuracy of the single-crystal results was maintained by numerous cross and redundancy checks. Compared to the single-crystal elastic properties of forsterite, Mg₂SiO₄, the fayalite stiffness constants, as well as their pressure derivatives, are lower for each of the on-diagonal (C _ij for which i=j) values, and generally higher for the off-diagonal (C _ij for which i≠j) data. As a result, the bulk moduli (K) and dK/dP for forsterite and fayalite are very similar, but the rigidity modulus (μ) and dμ/dP for polycrystalline fayalite are much lower than their forsterite counterparts. The bulk compression properties derived from this study are very consistent with the static-compression x-ray results of Yagi et al. (1975). The temperature dependence of the bulk modulus of fayalite is somewhat greater (in a negative sense) than that of forsterite. The rigidity dependencies are almost equivalent. Over the temperature range relevant to this study, the elastic property results are generally consistent with the data of Sumino (1978), which were obtained using the RPR technique. However, some of the compressional modes are clearly discrepant. The elastic constants of fayalite appear to be less consistent with a theoretical HCP model (Leibfried 1955) than forsterite, reflecting the more covalent character of the Fe-O bonding in the former.     

Precursory quiescence before the August 1982 Stone Canyon,San Andreas fault,earthquakes

The Stone Canyon earthquake sequence started during August 1982 and lasted for about four months. It contained four mainshocks withM _L 4, each with an aftershock zone about 4 km long. These mainshocks, progressing from southeast to northwest, ruptured a segment of the fault approximately 20 km long leaving two gaps, which were later filled by theM _L =4.6 mainshocks of January 14, and May 31, 1986. The equivalent magnitude of the sequence isM _L =5.0.Precursory seismic quiescence could be identified in: (1) the northernmost 10 km of the aftershock zone which contained three of the mainshocks; and (2) the southern gap in the aftershock zone. The fault segment containing the first mainshock and its aftershocks did not show quiescence. This pattern of precursory quiescence is very similar to two cases in Hawaii where the rupture initiation points of the mainshocks (M _S =7.2 and 6.6, respectively) were located in volumes of constant seismicity rate, surrounded by volumes with pronounced precursory quiescence.The precursory quiescence before the August 1982 Stone Canyon earthquakes lasted for 76 weeks, amounted to a reduction in rate of about 60%, and could be recognized without any false alarms. That is, the anomaly was unique within the 60 km study segment of the fault and in the years 1975 through August 1982. Eighteen foreshocks occurred between July 27 and August 7, 1982. We conclude that the August 1982 mainshocks could have been predicted, based on seismic quiescence and foreshocks.