Closs, H. and Morelli, C. : Seismic Experiments in the Dolomites (Lago Lagorai) to investigate the Earth’s Crust in the Eastern Alpine Area . . . 249 ;
Müller, St, Stein, A. and Vees, R.: Seismic Scaling Laws for Explosions on a Lake Bottom . . . 258 ;
Koch, H., Sehminder, R. and Kürschner, D.: Ein neues automatisches Registriergerät für ionosphärische Driftmessungen . . . 28l ;
Israel, H. and Haas, R.: Absorption of natural fallout in soil . . . 289 ;
Buchbesprechungen . . . 293 ;
CLOSS, H. and MORELLI, C. : Seismic Experiments in the Dolomites (Lago Lagorai) to investigate the Earth’s Crust in the Eastern Alpine Area. Summary: The “Sous-Commission des Explosions Alpines” carried out a series of explosions; the aim of experiments is described, the choice of a lake as shotpoint is discussed, operational details are illustrated, data on seismic parties and instruments are tabulated. - - -
MÜLLER, St, STEIN, A. and VEES, R.: Seismic Scaling Laws for Explosions on a Lake Bottom. Summary: In September 1961 a series of 22 explosions was set off for experimental purposes on the bottom of a lake near Trento in Italy. During these tests the Charge size varied between 2 and 760 kg of TNT. A11 shots were recorded along three refraction profiles using calibrated equipment. The maximum recording distance was 168 km.
Three seismic stations were kept at the same locations during the entire operation. Their main object was to determine the relationship between ground amplitudes of first arrivals and weight of the explosive Charge. The distances between the shotpoint and these permanent stations were 1.50, 21.15, and 34.05 km, respectively.
The response curves of the instrumental equipment are discussed. Examples of seismograms are shown which demonstrate that the frequency spectrum of the first arrivals does not change systematically with increasing charge size. Characteristic second and later arrivals, clearly recorded in a distance of 21.15 km, must be interpreted as signals radiated from the rising gas bubble. It must be ascribed to the low background noise level that excellent seismograms could be obtained in a distance of 34.05 km from the shotpoint even with charges as small as 5 kg.
The amplitudes of true ground motion were determined for first arrivals. Ten sets of data were then ﬁtted to power laws of the form: ɑ = const · Wn (ɑ = amplitude in mµ; W = charge weight in kg)
by least-square methods. The average value of the exponent n equals 0.65 for the entire series, while the mean deviation of the individual values from the power functions is about 16 per cent.
If the relation between seismic amplitudes and Charge weight is plotted on a log—log scale a systematic curvature is noticed for some sets of data which indicates that a simple power law is not sufﬁcient to ﬁt the observations. This eﬁect has been investigated more closely for two sets of the experimental data. - - -
KOCH, H., SEHMINDER, R. and KÜRSCHNER, D.: Ein neues automatisches Registriergerät für ionosphärische Driftmessungen. Summary: A recorder for ionospheric drift measurements according to KRAUTKRÄMER’S method is described, which allows of directly the time differences between corresponding extremes in the signal voltage curves. The apparatus offers economy in operation and in evaluation of measurements and permits of making continuous registrations. Comparative measurements using conventional techniques have shown that, in spite of some inherent limitations, the apparatus is capable of yielding sufficiently accurate mean values of drift velocity and drift direction. - - -
ISRAEL, H. and HAAS, R.: Absorption of natural fallout in soil.
Summary: lt is shown by Laboratory experiments on the problem of fall-out distribution in soil that radioactivity is absorbed in the uppermost layers of the ground. The measurements were made by sprinkling water activated with ThB on different types of soil. The distributions in the soil are found to be very similar t0 these of the Sr90-fallout. By these results the conclusion is justified that ThB can be used as tracer to detect the fall-out distribution in soil.