Seismotectonic scheme of Central and Eastern Europe

Summary The distribution of earthquake foci in the crust and the upper mantle indicates the position of mobile zones. Comparing epicentral maps of Central and Eastern Europe, known tectonic lines, results of deep seismic sounding and gravimetric survey enables a scheme of potential seismogenic zones, which correspond to active fault zones separating plates and blocks in the area, to be compiled. The level of earthquake activity varies along the investigated boundaries and can be considered as a measure of the intensity of the present geodynamic processes.Paper presented at the joint symposium AlO of the XVIIth General Assembly of the European Seismological Commission and of the 7th Annual Meeting of the European Geophysical Society, Budapest (Hungary), Aug. 21. – 29., 1980.     

Analysis of beam nulling of a sharpe gravity meter

Summary The routine nulling procedure is modified on the basis of the theoretical decay of transient motion of the gravity meter beam and the time needed for its stabilizing.     

The relation between the magnitude derived from surface and from body waves for station průhonice

auam aum¶rt;, m u n¶rt; n a¶rt;u u nm a anu, umua a u mauu u 1964–1976 . ¶rt; aum¶rt; ma auau aum¶rt;, n¶rt; uu m .     

Worldwide variations in the attenuative properties of the upper mantle as determined from spectral studies of short-period body waves

A worldwide study of short-period teleseismic body wave spectra shows that the high frequency falloff rates of spectra are correlated with the tectonic type of the source and receiver regions and with source depth. The data indicate, in a consistent manner, that the main cause for such variations is the lateral variation of Q in the upper mantle as well as change of Q with depth. Using the internal consistency checks provided by redundancies in the data set other effects such as crustal, site dependent distortion of the spectra, source effects and instrument non-linearity can be ruled out as significant factors influencing the $\text{t1}$ estimates obtained. The results indicate high attenuation in the upper mantle under tectonic regions and new oceans. Long-period regional attenuation studies indicate similar variations in mantle Q among the types of regions mentioned but yield significantly lower Q estimates in all areas. The short- and long-period attenuation results can be reconciled only by assuming a frequency dependent Q that increases with frequency along all types of paths, such that the relative differences in Q along various types of paths retain the same sign over the short- and long-period bands.     

我国北方和西南一些地区谷物天气产量变化与大型环流长期振动的分析

本文揭示了我国北方和西南一些粮产区的天气和谷物天气产量存在着60—70年的长期振动,并有特定的大型环流系统的长期振动与之相配合。提出了北方和西南的“环流-天气-天气产量”同步振动模式。简言之,当冬春季节亚欧大陆冷高压偏弱和南印度洋高压偏强,相应地,夏季赤道低压偏弱和西太平洋台风发生数偏少时,我国北方处于多水期、西南处于少水期,北方和西南地区的谷物天气产量偏高。反之,北方处于少水期、西南处于多水期,谷物天气产量偏低。     

1914——1965年发生在我国境内Ms≥4(3/4)地震参数的修定

本文对1914—1965年发生在我国境内Ms≥(4 3/4)的地震,用电子计算机进行了参数的修定,並简要介绍了修定的方法及修定的结果。结果表明,经过重新计算后,各参数(O.λ.φ.h)的精确度均有明显的提高。     

Natural nuclear reactors and ionizing radiation in the Precambrian

The natural nuclear reactors were geological arrangements of uranium and water where, like the 2 Ga-old uranium deposits discovered in Oklo (Gabon, Africa), uranium chain fission processes took place. Ten years after its discovery the phenomenon of Oklo is still neglected in Precambrian evolutionary studies. We consider some probable reasons for this and show that natural reactors might have been important, specific, localized sources of ionizing radiation during both the criticality and shut-down periods. Some of the long-lived fission products which migrated from the reactor core could also have been effective radiation energy sources after fixation in the environment or upon uptake by the earliest forms of living matter. The results presented here concern the examination of conditions for nuclear criticality on the Precambrian Earth, the dose-rates of ionizing radiation available and the estimate of the number of natural nuclear reactors that could have been active in the past.     

Corrigenda

Corrigendum

Corrigenda     

Earthquakes in the Czech Republic and Surrounding Regions in 1995–1999

In the time span from January 1995 to December 1999 the Czech National Seismological Network (CNSN), consisting of ten permanent digital broadband stations, several local networks and two data centers, detected and recorded 9530 regional natural seismic events, 27 greater than magnitude 2. Most of these events were located by the Czech Seismological Service (CSS), and the most prominent of them were analyzed in detail. A large number of quarry blasts were recorded as well but were not included in the analysis. We provide basic information on the configuration of the CNSN and on the way of routine data processing employed by the CSS in this paper. The over-all regional seismicity monitored by the CNSN in 1995–1999 is briefly reviewed. The main results of observations and evaluation of the local (NW-Bohemia/Vogtland, South Bohemia, Sudeten) and induced (Kladno, Píbram, Upper Silesia, Lubin/Poland) seismic activity within this period are presented in a condensed form. Finally, a summary on macroseismic observations on the territory of the Czech Republic in 1995–1999 is also presented.