Borehole Seismology and the Study of the Seismic Regime of Large Industrial Centres

ISBN-13: 9789027719676 / Angielski / Twarda / 1986 / 316 str.

E. I. Galperin; I. L. Nersesov; R. M. Galperina

Opis

Advances in seismology and extensions of its application have made it increasingly necessary to perform high-sensitivity observationsonartificial earth tremors (explosions) or on natural ones. This implies in particular to investigating the seismic conditions in large industrial centres. There are many major cities with a million inhabitants or more in seismically-active regions. In the USSR, this applies to the capitals of the Union Republics such as Alma Ata, Frunze, Tashkent, Dushanbe, and Ashkhabad, as well as to dozens of local entres and cities with extensive industrial development. Seismic classification and earthquake forecasting have to be considered in relation to the extension or building of cities in such regions, and this would be impossible without detailed investigation of the seismicity, which involves upgrading the instru- mental observation network. The demand for detailed information on the seismicity increases with every extension to the construction. A successful solution here can be implemented only by taking account of some specific factors, the main one being the high level of seismic noise due to the activities in large centres, which restricts the sensitivity of the apparatus and makes it impossible to record weak local earth tremors, which are of particular interest in periods of relative seismic calm. Stations at sufficiently great distances from the city do not sense the city noise, but they also fail to record weak local earth tremors. Also, the accuracy ofobservation falls for those tremors that can be recorded because of the great distances between stations.

Spis treści

I: Borehole Seismology.- 1/Borehole Observation Apparatus.- 1.1. Borehole Seismometers.- 1.2. Preamplifiers.- 1.3. Recording Equipment.- 2/Noise in Boreholes.- 2.1. A Brief Survey of the Literature on Borehole Observations.- 2.2. Noise Waves of Man-Made Type.- 2.3. Depth Variation of Seismic Noise Level.- 2.4. Background Stability at Various Depths.- 3/Seismological Observations in Boreholes.- 3.1. Observations with High Surface Noise.- 3.2. Observations at Small Depth with Low Surface Noise.- 3.3. Observations in Areas of High-Velocity Crystalline Rocks.- 3.4. Observations in the Presence of Stationary Noise Sources.- 3.5. Observations in Shallow Boreholes Reaching the Crystalline Basement.- Conclusions to Part I.- II: Study of Seismic Conditions in Large Industrial Centres, with Reference to Alma Ata.- 4/Geological and Geophysical Characteristics of the North Tien Shan.- 4.1. Tectonic Classification.- 4.2. Geophysical Information and the Deep Structure of the Region.- 5/Seismicity in the North Tien Shan.- 5.1. Strong Earthquakes in the North Tien Shan.- 5.2. Instrumental Data on North Tien Shan Seismicity.- 5.3. Seismic Regime.- 6/The Alma Ata Seismological Radio Telemetry Polygon.- 6.1. Polygon Structure and Technical Parameters.- 6.2. Effects of Observation Conditions at Polygon Stations on Remote-Earthquake Recording.- 6.3. Effects of Observation Conditions on Local Earthquake Recordings.- 6.4. Azimuthal Deviations in the Seismic Rays from Remote Earthquakes.- 7/Observational Data and Processing Methods.- 7.1. RTS Working Characteristics and Resulting Data.- 7.2. Processing Methods.- 7.3. Energy Classification.- 7.4. Explosion Recording.- 8/Spatial Characteristics of Seismic Regime.- 8.1. Seismogenic Zones.- 8.2. The Seismic Background Density.- 8.3. Depth Distribution of Earthquake Foci.- 8.4. Spatial Distributions of Earthquakes with Various Energies and Earthquake Recurrence.- 8.5. The tS?P Distribution.- 9/The Time Features of Seismic Regime.- 9.1. Focus Migration.- 9.2. Spatial and Time Seismicity Characteristics in Earthquake-Focus Concentration Regions.- 9.3. The Time Characteristics for Earthquakes of Various Energies.- 9.4. Periodicity in Seismic Activity.- 9.5. Prognostic Features of Weak Seismicity.- Conclusions to Part II.- Postscript.- References.- Appendix I: Annual epicentre maps.- Appendix II: Local earthquake bulletin.- List of Abbreviations.- Index of Subjects.