No abstract available

[en] A 1976 treaty between the United States and the Soviet Union permits a local seismic network to be deployed at the site of a peaceful nuclear explosion to monitor the event. Criteria for the design and selection of the data-acquisition equipment for such a network are provided. Constraints imposed by the protocol of the treaty, the environment, and the expected properties of seismic signals (based on experiences at the Nevada Test Site) are discussed. Conclusions are drawn about the desired operating mode. Criteria for a general seismic instrumentation system are described

[en] Receiver functions (RFs) obtained using teleseismic wave records at a seismic station and synthetic seismograms indicate that RF with a single teleseismic wave record is related to the selection of record section and to the calculating parameters of the RF. The scatter noise contained in the seismogram also affects the quality of RF. A new method for calculating receiver function, stacking and smoothing multi-seismic records in a single station, is presented in this paper. The RF results using some records and some synthetic seismograms with different noises indicate prominent mantle discontinuity and thus prove that the method is effective and satisfied.

[en] Methods of seismic detection of nuclear events are investigated in the Government sponsored research reports. Data acquisition techniques, data processing, and data collection sources are reviewed. The updated bibliography contains 246 abstracts, 101 of which are new entries to the previous edition. See also NTIS/PS-76/0208, Volume 2, 1973-1974 and NTIS/PS-76/0207, Volume 1, 1970-1972

[en] Seismic data from two explosions was processed using the Systems Science and Software MARS (Multiple Arrival Recognition System) seismic event detector in an effort to determine their relative spatial and temporal separation on the basis of seismic data alone. The explosions were less than 1.0 kilometer apart and were separated by less than 0.5 sec in origin times. The seismic data consisted of nine local accelerograms (r < 1.0 km) and four regional (240 through 400 km) seismograms. The MARS processing clearly indicates the presence of multiple explosions, but the restricted frequency range of the data inhibits accurate time picks and hence limits the precision of the event location

[en] This report describes the progress being made in event location using a single 3-component station. In this study locations are obtained using a backazimuth determined by the particle motion of Pn and a distance determined by differential travel times between Pn, Pg, and Lg relative to a master event of known location. The data set used consists of the seismic signals from 11 nuclear events at the Nevada Test Site (NTS) and recorded at the four Lawrence Livermore National Laboratory (LLNL) seismic stations: Elko, Kanab, Landers, and Mina. The stations range from 230 km to 400 km away from the events. The local magnitude (M/sub L/) of the events range from 3.7 to 5.6 with the small events barely visible over the microseisms. All calculations and observations are made after the events have been filtered between 0.3 and 6 Hz. The results of this analysis show that backazimuth can be determined to within +- 5₀ of the true backazimuth, about 90% of the time, after systematic variations are taken out

[en] Seismic noise has been studied in a wide range of frequencies (more than 6 orders). The seismic noise density spectrum has compared with seismic noise models, obtained for observations of the Global Seismic Network. The parameters characterizing variations of seismic noise from technological and natural sources were estimated. (author)

[en] The site and intensity of nuclear weapons tests can be reliably determined by measurement and suitable interpretation of seismic waves. A seismic focus is up to 20 times larger than the destruction zone of a comparably strong explosion, so that a seismic event will last longer by one order of magnitude than an explosion. Nuclear weapons tests induce much more high-frequency vibrations than a seismic event, and a seismic event normally proceeds in a series of subsequent shocks. Diaphragms applied in the range 10 to 30 Hz considerably improve the signal-to-noise ratio of systems for the detection of nuclear weapons tests. (orig./DG)

[en] Since 1969, a consistent discrepancy in seismic magnitudes of nuclear detonations at NTS compared with magnitudes of detonations elsewhere in the world has been observed. This discrepancy can be explained in terms of a relatively high seismic attenuation for compressional waves in the upper mantle beneath the NTS and in certain other locations. A correction has been developed for this attenuation based on a relationship between the velocity of compressional waves at the top of the earth's mantle (just beneath the Mohorovicic discontinuity) and the seismic attenuation further down in the upper mantle. Our new definition of body-wave magnitude includes corrections for attenuation in the upper mantle at both ends of the teleseismic body-wave path. These corrections bring the NTS oservations into line with measurements of foreign events, and enable one to make more reliable estimates of yields of underground nuclear explosions, wherever the explosion occurs

[en] In first information about earthquakes in so-called 'aseismatic' regions of Kazakhstan obtained by the Institute of Geophysical Research of the National Nuclear Center of the Republic of Kazakhstan specialists were published. Until recently central Kazakhstan was not in part of seismically active regions of Republic. With putting into operation the NNC RK station network, a number of earthquakes with magnitude up to 5.0 were registered. In the present work focus mechanisms for two seismically active zones of central Kazakhstan were determined for the first time. Mode of deformation characteristics of this region which compared with seismotectonic deformation parameters of Northern Tien-Shan and Djungary were established. Obtained results are very important for understanding the geo dynamic processes on vast territory of Central Asia. (author)