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The analysis of P-wave magnitudes for 37 shallow earthquakes of the Alpine-Himalayan tectonic belt determined by the Homogeneous Magnitude System (HMS) technique using short- and medium-period standard instruments is carried out. The results are compared with spectral magnitudes obtained with the broadband instrument with digital registration at the Central Seismological Observatory (Grafenberg, FRG). It is shown that for the majority of the earthquakes the HMS magnitudes reveal basic spectral features of seismic radiation from the shallow event foci, though they are insufficient for the analysis of complicated cases. Thus, both the HMS and the spectral magnitude approaches are complementary and highly desirable for seismological practice.

After a special investigation into the stability of seismic stations of the Eurasian continent, a system of reference stations for routine determination of earthquake magnitudes has been selected. A method for determining station corrections in a network of continental dimensions has been developed and tested for PV waves observed by eight Eurasian stations, taking into account the dependence of station corrections on source region. It is assumed that such a homogeneous system of reference stations can eliminate the largest discrepancies in the magnitude determinations.

Amplitude curves for seismic P-, S- and L-waves have been constructed on the basis of the homogeneous magnitude system of the Eurasian continent. The optimum amplitude curves are compared with the standard amplitude curves used in seismological practice.

Routine determination of network magnitudes by means of the Eurasian homogeneous magnitude system (HMS) is described and tested on a selection of recent shallow earthquakes. The HMS earthquake magn ...

Causes of inconsistency in magnitudes determined by broad-band and short-period instruments and by different systems of observations are elucidated. In so doing, both observations of standard stations of USSO of the USSR and those of Soviet frequency selecting seismic stations (чисс) are employed. On the basis of large statistic material of the stationare network of USSO, a dependence of spectral constitution ofP waves and frequency-temporal fields constructed for some earthquakes have been revealed as well as a dependence of magnitude values upon an arrival time of maximal particle velocity. It has been shown that the range of measuring (A/T)max should be enlarged at least to 15 sec. A conclusion is drawn that the most stable magnitude consistent with the Catalogue by Gutenberg is the one determined by medium-period instruments.