Release test with electromagnetic seismograph

u¶rt; am ¶rt; mua maum aa nu ¶rt;uu ma n¶rt;a mnu ma auau am. a¶rt;¶rt;a mu m¶rt; auu a¶rt;am n¶rt;um m nm aa u n uu naua nu¶rt;a ma uuaama aumam ma nm aa u uu uuma u.     

Sensitivity of the Sharpe and Worden gravity meters to vertical motion

Summary Using the least-squares method the constants of both gravity meters — seismometers — were derived from the amplitude responses, observed under vertical motion on a vibrating table in the 0.3–30 s range. The values of the seismogram amplitudes, above which seismic waves cause an observable displacement of the gravity meter reading beam, were determined for the SKD and Press-Ewing station seismographs.     

Estimate of the effect of vibrations on quartz gravity meters

Summary Relations for computing the minimum amplitudes of ground vibrations which generate oscillations of the gravity meter reading beam at the limit of the resolution of the optical system, have been derived. The minimum amplitudes in the ground displacement period range of0.1 to10 s, for the assumed values of the fundamental parameters of quartz gravity meters (i.e. the periods and damping constants of the pendulum and the mechanico-optical magnification of the pendulum deflections), range from tenths of a micrometre to units of micrometres. Larger displacement amplitudes, due to, e.g., earthquakes and traffic, disrupt gravity measurements.     

Rheological modelling of measuring systems of quartz gravity meters

Summary Some phenomena, recorded during pressure tests of quartz gravity meters, are studied theoretically using a model of the visco-elastic continuum. Expressions, describing the response of the measuring system as a function of the time variation of pressure disturbances, are derived by solving the appropriate rheological equations.

---

n ¶rt;u n uu u¶rt; u, uu uu unu ¶rt;u u. u u uu u ¶rt; u nuu u uu u uuu ¶rt; u ¶rt;u.

     

The effect of the magnetic field on the accuracy of measurements with Worden and Sharpe gravity meters

Summary The effect of an additional homogeneous magnetic field with an intensity of 0–4.5 Oe on the Worden quartz gravity meter No. 961 and on Sharpe quartz gravity meters Nos 173 and 174 was tested. Whereas no effect was observed with the Worden gravity meter, the magnetic field had a measurable effect on both the Sharpe gravity meters. The largest deviation of the reading beam is caused by the horizontal component of the magnetic field which acts in the plane of oscillation of the gravity-meter arm. The Sharpe gravity meter No. 173 is considerably sensitive; a field of 0.2 Oe intensity, corresponding to the magnitude of the horizontal component of the geomagnetic field in mid-latitudes, causes an error in the measurement of gravity of as much as 0.08 mGal. With a view to the different behaviours of the individual quartz gravity meters of the same type in a magnetic field, it should prove expedient to carry out check measurements with all gravity meters and, with regard to the sensitivity of the gravity meter to the magnetic field and the required accuracy of the gravity determination, take into account this perturbing factor in field measurements, as well as laboratory tests of gravity meters.     

Variations of the geomagnetic field along the dss profile no. VI in Czechoslovakia

Summary The ratios of the amplitudes of bay-type variations of the geomagnetic field along the DSS profile VI to the amplitudes of the same phenomena recorded at permanent geomagnetic observatories at Prhonice and Budkov were studied. The relative variations of the values of the horizontal component, declination and, particularly, the vertical component of the geomagnetic field indicate deep fault zones.     

The effect of the galvanometer coupling on the accuracy of measuring the seismometer constants of an electromagnetic seismograph

Summary The errors in determining the partial constants of a seismometer using the method of recording the free oscillations of the seismometer by a galvanometer are analysed and the maximum values of the coupling coefficients at which the derived seismometer constants do not differ from the partial by more than 1%, are computed.