Seismic hazard computations for regions with low earthquake activity — A case study for the Belgium,The Netherlands and NW Germany area

The algorithms to evaluate seismic hazard, used and/or developed by five teams participating in the TERESA project, applied to the low seismicity area Belgium, The Netherlands and NW Germany are compared. The main differences in the results can be explained by the majority criterion of Egozcue et al. (1989), the differences in the upper bound and zonification and, in some cases, by a higher attenuation.     

On the relation between solar motion and the long term variability of solar activity

Summary The Sun's motion round the barycentre of the solar system was found to consist of two basic alternately repeating elements of the noose and of the arc. The mean time for solar motion around each of these elements was found to be 9.93 yr. The relation between solar motion and solar variability was determined as follows: Approximately coincident periodicities ranging from 60 to 2200 yr were traced in both phenomena and a coincidence of all prolonged minima in solar activity with the epochs of the highest deviations from the Jupiter—Saturn order was found over a time interval of 3100 yr.

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ma, m ¶rt;uu a ma mmu um mum u ¶rt; , n nmu m — u nmu u u au. uu a a¶rt; u mu m ¶rt;um ¶rt; 9.93¶rt;a. am a maa ¶rt; ¶rt;uu a u au amumu: a mu m n¶rt;anum—am a aa nuuum maa u¶rt;um ¶rt;uuu a n¶rt;ea 60–2200 m, a u amumu, a mu umaa ¶rt;umm 3100 m a¶rt; n na¶rt;u ¶rt; uu amumu nu¶rt;au aua mu m n¶rt;a — u am.

     

Stick-slip unstable shear failure as a source of high frequency elastic radiation

Summary The results of laboratory measurements on square perspex models with a stress concentrator under uniaxial compression are presented. An attempt was made to interpret these results in order to determine the mutual relations between the mechanical parameters characterizing the treated models, including their focal zones, parameters of model loading, parameters of seismogenic displacement and parameters of radiated elastic pulses. Particular attention was given to the study of slip displacement, slip velocity, rupture velocity, nucleation points of rupture propagation, nucleation points of elastic radiation and to the frequency analysis of radiated pulses. Measurements of the displacement in the focal zone enabled us to determine the source function, to construct theoretical seismograms in a far field and to compare them with the real pulses from ultrasonic transducers located there. This allowed testing theoretical and experimental approaches to the study of how slip displacement, slip velocity and rupture velocity are related to the parameters of radiated pulses.     

Measurement of a freezing nucleus content in a water sample — Evaluation of the method

Summary A drop freezing technique applied in laboratory research to heterogeneous ice nucleation is described. The quality of the obtained experimental data is studied both theoretically and experimentally. Attention is focused on the range of measurable freezing nucleus concentration, the accuracy, the correctness and the reproducibility of the results. Some mechanisms which could influence the correctness of the method are discussed. No mechanism significantly influencing the measurements was found. It is concluded that the present experimental method is an effective method of measuring a freezing nucleus content in a water sample.

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ama na uu m¶rt;a n¶rt;u mauu ¶rt; ¶rt; a ¶rt;. ¶rt;m ama mam n nuu m¶rt;a. uau ua a ¶rt;uana uum mauu ¶rt; ¶rt;, a mm, naum u nmumm mam. umum m uu a naum m¶rt;a, m u u ma.

     

Strato-mesospheric ozone and IMF sector boundary

Summary We find no effect of the interplanetary magnetic field(IMF) sector boundary crossing in ozone at altitudes ranging from the middle stratosphere(10 hPa) to the lower mesosphere(0.4 hPa) at middle latitudes(40°–60° N), based on winter data over the period of December 1979–December 1982.

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Резюме Мы не нaшлu нuкaко о эффекma nересеченuя секmорноŭ рaнuцы межnлaнеmно о мa нumно о nоля в озоне в облaсmu высоm меж?rt;у сре?rt;неŭ сmрamосфероŭ(10 Пa) u нuжнеŭ мезосфероŭ(0,4 Пa) нa сре?rt;нuх шuроmaх(40°–60° с.ш.), nрuменяя зuмнuе ?rt;aнные зa nерuо?rt; ?rt;екaбрь 1979 – ?rt;екaбрь 1982 .

     

Geomagnetic field from the Earth's core: Its westward drift rate and some probable global-tectonics implications

Summary Sets of virtual poles corresponding to sets of geomagnetic field values at equidistant points, lying along circles of latitude, were defined on the basis of the 1980 IGRF extending to degree and order 8. Certain places on the Earth's surface yield virtual poles lying very close together. The segments of the virtual pole paths, corresponding to these places, have a large curvature. The mentioned places of the Earth's surface are supposed to be areas with a low rate of the westward drift. They form continuous zones that show a certain relation to global-tectonics features.

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uum ¶rt; 8- n¶rt;a ¶rt;a¶rt; aaumu n 1980 u u nmu uma n, mmmu nm uu n ma, a u¶rt;umam ¶rt; naa m ma nmu nua¶rt;am uma n, m uu ¶rt; ¶rt;. amu u, mmmu mu ma, um uu. ¶rt;naam, m nm ma nmu m amu, m m ana¶rt; ¶rt;a ua. u am n na, m naam a m uua mmuu.

     

Statistical analysis of values measured in condensating geodetic nets

Summary Procedure for verifying the agreement between parameters common to the basic and connecting trigonometric net. Procedure of determining the accuracy of the connecting net. This determination concerns not only the relativized accuracy of the points of the connecting network, but also the mutual accuracy of the points of the basic net relative to the points of the connecting net and the global accuracy of the resultant net. The procedure takes into account the accuracy of the points of the basic net which remain unchanged in computing the coordinates of new points.

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m¶rt; ¶rt; nu au u naam¶rt;mu u nu¶rt;u m. m¶rt; ¶rt; u mmu nu¶rt;u mu. a aam m mum nua mmu m nu¶rt; mu, ma au mmu m mu n mu ma nu¶rt;u mu ua mmu mu mu. m¶rt; umam mm m mu, m aa uu ¶rt;uam m mam uu.

     

Experimental investigation of turbulent processes in a complex terrain

In the present paper the first results of the international KOPEX-86 experiment are presented. The experiment took place at the Kopisty Atmospheric Observatory of the Institute of Physics of the Atmosphere in Prague as part of a special project of the Commission of the Academy of Sciences in Planetary Geophysics (KAPG) in June and July 1986. Using 4 ultrasonic anemometers at 4 levels up to 80 m, Doppler-SODAR and wind-, temperature- and radiation balance gradients from 2 to 80 m, a complex investigation of the atmospheric boundary layer in an industrial area was made. The authors present the first results of

Tidal deformations of viscoelastic body

Summary The tidal deformations of a viscoelastic body are studied using the simple Kelvin-Voigt model. Expressions for the phase lag and amplitude change of the displacement vector are derived. The energy dissipation rate is calculated for the main disturbing bodies and for diurnal and semidiurnal tidal waves.

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am nuu ¶rt;auu n ma ua-ma. ¶rt; au ¶rt; ana¶rt;au a u uu anum¶rt; ma u. aumaa m ¶rt;uunauu uu ¶rt; u a a m u nm .