Broadband seismograms of body waves that are flat to displacement and velocity in the frequency range from 0.01 to 5.0 Hz can now be routinely obtained for most earthquakes of magnitude greater than about 5.5. These records are obtained either directly or through multichannel deconvolution of waveforms from digitally recording seismograph stations. In contrast to data from conventional narrowband seismographs, broadband records have sufficient frequency content to define the source-time functions of body waves, even for shallow events for which the source functions of direct and surface-reflected phases may overlap. Broadband seismograms for selected IASPEI events are systematically analysed to identify depth phases and the presence of subevents. The procedure results in improved estimates of focal depth, identification of subevents in complex earthquakes, and better resolution of focal mechanisms. We propose that it is now possible for reporting agencies, such as the National Earthquake Information Center, to use broadband digital waveforms routinely in the processing of earthquake data. ?? 1987.
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Analysis of broadband seismograms from selected IASPEI events