VERIFICATION OF MAGNITUDES OF HIMALAYAN REGION EARTHQUAKES OF 1903-1985 FROM GOTTINGEN OBSERVATORY

From the microfilms of Gottingen Observatory seismograms, magnitudes a re verified for thirty-seven major and great earthquakes (magnitude gr eater than or equal to 7) in the Himalayan region for the period 1903- 1985. Duda (1992) had earlier determined magnitudes of these earthquak es from Gottingen records. There were three other major earthquakes fo r which magnitudes could not be determined, as their records from Gott ingen were not found. The magnitude values were determined using P-, S - and surface waves from long- and medium-period instruments. The magn itudes from short-period P- and S-waves were not redetermined to avoid uncertainties of such measurements from the microfilms. As compared t o Duda (1992), the present values of the surface-wave magnitudes corre sponding to 20+/-3 s period from horizontal components are found to be higher for nine earthquakes by 0.2-0.5 units. The body-wave magnitude s are similarly changed. These changes bring the magnitudes closer to the values given in earlier catalogs. The relative quiescence after 19 50 is striking. The seismogram portions of earthquakes (magnitude grea ter than or equal to 7.5) are reproduced.