APPLICATION OF ANALOG-DIGITAL CONVERTER FOR SEISMIC DATA

An analog-digital converter is applied for analysis of seismic data. This apparatus is generally designed for digitizing the analog data recorded on magnetic tape. The maximum sampling speed is 3, 000 per sec. Some results for the aftershocks of the Niigata Earthquake are shown

An Analysis of Strong Motion Accelerograms near the Epicenter

The strong motion accelerograms of the Matsushiro earthquake were analyzed by various methods. When the velocity and the displacement in the time domain and in the frequency domain are calculated from the accelerogram, various errors may be introduced. Therefore, it is necessary to check and select the methods of data processing according to the purpose of analyses. In this paper, it was shown that the comparison of observed values with theoretical in the form of velocity amplitude spectral density might be most preferable. The main factors affecting the ground vibration during disastrous earthquakes are generally conceived to be: source, path and local geology. The relations between the observed seismogram and the theoretical one were compared when a moving dislocation model was assumed. It was found that the direction of particle motion and the spectral density of observation could be reasonably understood from the theoretical point of view

Vibrational Characteristics of the Ground Investigated by Several Methods

The vibrational characteristics of the ground were investgated through the observation of natural earthquakes and blasts and by means of an oscillator and seismographs being set on the ground surface and in the drift. Fourier components were obtained in the case of seismograms of natural earthquakes and blasts, and the amplitude-frequency relations for a constant vibrational force in the case of vibrational test by the oscillator. The ground structure was rather complicated, however, the amplitude and phase distributions at each measuring point (on the ground surface and in the dirft) coincide well with that of theoretical calculations in regards to the ground structure and the spectrum of the place

大発破に関する研究(I) ―発破計画および爆薬について―

In order to discuss about the method and the explosives for the coyote blasting and also themethod for verifying whether whole charges have been detonated or not, a specially designedcoyote blasting was carried out at Maeshima, Ushimadocho Okayama prefecture, on 18th April1962.Rocks around test site is a kind of granite. In this blasting, 11 chambers were formedwithin rocks and these were filled up with proper explosives. Total weight of explosives filledup in these chambers were about 6, 500 kg, and these explosives were fired by some delay de-tonators. The time from the instant of detonation of the initial chamber to that of the last wasabout 4, 000 ins.Some high speed moving camera and some pick-up which were used for observing the vi-bration of rocks caused by these explosions were used for verifying the detonation of each ex-plosive.It was recognized on this coyote blasting that the breakage of rocks by the delay blastingwas better than that by the instantaneous blasting, therefore, the delay blasting was useful inthe coyote blasting as same as the general blasting which was performed by the explosives load-ed in some drill holes, and also the verification of detonation was more easily on the delayblasting, therefore, adopting the delay blasting method to the coyote blasting was available onthe stand point of safety in operations.In order to discuss about the method and the explosives for the coyote blasting and also themethod for verifying whether whole charges have been detonated or not, a specially designedcoyote blasting was carried out at Maeshima, Ushimadocho Okayama prefecture, on 18th April1962.Rocks around test site is a kind of granite. In this blasting, 11 chambers were formedwithin rocks and these were filled up with proper explosives. Total weight of explosives filledup in these chambers were about 6,500 kg, and these explosives were fired by some delay de-tonators. The time from the instant of detonation of the initial chamber to that of the last wasabout 4,000 ins.Some high speed moving camera and some pick-up which were used for observing the vi-bration of rocks caused by these explosions were used for verifying the detonation of each ex-plosive.It was recognized on this coyote blasting that the breakage of rocks by the delay blastingwas better than that by the instantaneous blasting, therefore, the delay blasting was useful inthe coyote blasting as same as the general blasting which was performed by the explosives load-ed in some drill holes, and also the verification of detonation was more easily on the delayblasting, therefore, adopting the delay blasting method to the coyote blasting was available onthe stand point of safety in operations

大発破に関する研究(II) ―爆破点近傍の振動測定―

The ground motions near shot point are measured at various places, that is, in the quarryand on the ground surface of each different geological structure. The weights of charge are inthe range of 0.1-1 tons and the distances from shot point and measure points are 20--~--120 in.It is confirmed that the displacement, particle velocity and acceleration of the ground motioncaused by explosion are largely related to the blasting conditions, geological structure of themeasure point and the path through which the waves passes. Especially, the tainping of thecharge and the shape of the free surface before the blast are mainly concerned with the emis-sion of elastic waves from the shot point. The size of rock fragments after the blast is foundto be a function of C which is expressed by C=a/W'/'d'. (a: amplitude, W: weight of charge, d: distance between shot point and measure point.)The ground motions near shot point are measured at various places, that is, in the quarryand on the ground surface of each different geological structure. The weights of charge are inthe range of 0.1-1 tons and the distances from shot point and measure points are 20--~--120 in.It is confirmed that the displacement, particle velocity and acceleration of the ground motioncaused by explosion are largely related to the blasting conditions, geological structure of themeasure point and the path through which the waves passes. Especially, the tainping of thecharge and the shape of the free surface before the blast are mainly concerned with the emis-sion of elastic waves from the shot point. The size of rock fragments after the blast is foundto be a function of C which is expressed by C=a/W'/'d'. (a: amplitude, W: weight of charge,d: distance between shot point and measure point.

PRELIMINARY REPORT OF LOCAL SEISMIC ACTIVITY AROUND SYOWA STATION, EAST ANTARCTICA

A local earthquake with 20s S-P time was recorded at two seismic stations (Syowa and Tottuki) with three-component seismographs in Lutzow-Holm Bay, Antarctica in June 1987. The earthquake was located at about 170km northeast of Syowa Station. Its magnitude was estimated to be about 1.8. Other ten earthquakes of 20s S-P time were recorded by a test small tripartite seismic array in East Ongul Island during March 1987. The east Antarctic shield has been considered to be an aseismic area. It becomes clear, however, that some local earthquakes are located in the marginal area of the east Antarctic continent