Magnitude scale structure from filtered broadbandP-wave records |
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| Authors: | A Roglinov J Horálek A Ple?inger J Vaněk |
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| Institution: | (1) Geophysical Institute, Bulgarian Academy of Sciencies, Moskovska 6, Sofia, Bulgaria;(2) Geophysical Institute, Czechoslovak Academy of Sciences, Bo ní II/1401, Praha 4-Spo ilov, Czechoslovakia |
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| Abstract: | A series of Hokkaido events, recorded by the FBV Broadband Seismograph System at the KHC Seismic Station, is used to study the structure of the earthquake magnitude scale on the basis of maximum velocity amplitudesA
vmax of teleseismicPwaves in different period bands. Amplitude-periodband (APB) diagrams are constructed for each event. According to the shape of the APB diagrams the events investigated can be divided into three types: (a) events with largestA
vmax values in the intermediate period range (periods ofA
vmax from 2.2 to 23 sec), (b) events with largestA
vmax values in the short-period range (periods ofA
vmax from 1 to 2 sec), (c) events exhibiting anomalous APB diagrams. Type (a) events seem to represent the process of wave generation that prevails for shallow earthquakes. Type (b) events approach to explosive-like generation of seismic waves. The nature of the exceptionally occurring type (c) events must be clarified in further investigations. The influence of the type of earthquake on the magnitude values estimated on the basis of standard class A and B (short-period and intermediate-band) seismograms is demonstrated. It appears that for estimating correct values of earthquake magnitudes complementary information on the process of seismic wave generation in the focus is necessary. At teleseismic distances this information can be obtained from either APB diagrams or amplitude spectra ofP waves recorded, e.g., by broadband velocity sensing instruments. |
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| Keywords: | Magnitude Earthquake magnitude Broad-bandP-wave records Hokkaido earthquakes |
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