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1
1987, 9(1): 52-64.
Abstract：
This paper discusses the calibration function used in the formula for determining local magnitude, ML, of earthquakes and the corrections for station site, instrument component, and the azimuth of the station with respect to the epicenter, on the basis of the data from 395 earthquakes (1.0ML6.2; 10 km△600km) recorded by the Beijing Telemetered Seismic Network during the period of 1978 to 1984. The research also stresses the different methods for the determination of magnitude MD by signal duration and the associated errors. The results indicate that the magnitude estimation can have a higher precision by using the method proposed in this paper. With signal duration data from only a few stations or even a single station, an unbiased estimate of magnitude can be obtained without any additional correction. It must be pointed out that the signal duration magnitude, MD, shows a tendency of saturation when the magnitude is greater than 4.8. In that case satisfactory results may be obtained by using another fitting equation with a greater slope.
This paper discusses the calibration function used in the formula for determining local magnitude, ML, of earthquakes and the corrections for station site, instrument component, and the azimuth of the station with respect to the epicenter, on the basis of the data from 395 earthquakes (1.0ML6.2; 10 km△600km) recorded by the Beijing Telemetered Seismic Network during the period of 1978 to 1984. The research also stresses the different methods for the determination of magnitude MD by signal duration and the associated errors. The results indicate that the magnitude estimation can have a higher precision by using the method proposed in this paper. With signal duration data from only a few stations or even a single station, an unbiased estimate of magnitude can be obtained without any additional correction. It must be pointed out that the signal duration magnitude, MD, shows a tendency of saturation when the magnitude is greater than 4.8. In that case satisfactory results may be obtained by using another fitting equation with a greater slope.
6
Abstract：
Changes in the occurrence frequency and AZ/AH of geomagnetic stroms are preliminarily analyzed using 22-year storm data of 1957-1978 at Beijing Observatory in this paper. Statistical results show that 23-00-01-02 h of universal time (UT) are superior hours, and March, April, September, October in a year are superior months for storm occurrence frequency. There is a relation between storm occurrence frequency and solar activity. Changes in the oc-cuirence frequencies of various storms have a periodicity that correlate with the 11-year cycle of solar activity to a certain extent. The change in △Z/△H of SC-type variations has 22-year and 1.4-year periodicities, but the periodicity is not distinct. The change in △Z/△H of the main phase of geomagnetic storms has 22-vear, 11-year, 1.1-year periodicities, and the spectral peak of the 1.1-year period is very noticeable.
Changes in the occurrence frequency and AZ/AH of geomagnetic stroms are preliminarily analyzed using 22-year storm data of 1957-1978 at Beijing Observatory in this paper. Statistical results show that 23-00-01-02 h of universal time (UT) are superior hours, and March, April, September, October in a year are superior months for storm occurrence frequency. There is a relation between storm occurrence frequency and solar activity. Changes in the oc-cuirence frequencies of various storms have a periodicity that correlate with the 11-year cycle of solar activity to a certain extent. The change in △Z/△H of SC-type variations has 22-year and 1.4-year periodicities, but the periodicity is not distinct. The change in △Z/△H of the main phase of geomagnetic storms has 22-vear, 11-year, 1.1-year periodicities, and the spectral peak of the 1.1-year period is very noticeable.
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