Analog analyses of seismograms recorded on magnetic tape

摘要: Routine recording of long-period seismometer signals in analog form on magnetic tape makes it possible to perform a wide variety analyses rapidly and efficiently. Examples seismic waves from eight distant earthquakes, large nuclear explosion, the microseism storm associated with hurricane illustrate some advantages this type recording. Inverse selective filtering, without filter phase shift, are used remove instrumental effects, improve signal-to-noise ratio, emphasize desired phases. Fourier, energy, power spectrums obtained by several methods. Comparison results an Fourier analysis Palisades record Soviet explosion near Novaya Zemlya 1961 digital two smaller 1958 explosions same area recorded at shows remarkable similarity spectrums. The only significant difference between sets data is that larger event richer energy. Plots frequency versus time cumulative signal, different bands, present more convenient for certain studies than conventional record. Various combinations original three-component (N-S, E-W, vertical) permit easy identification wave types surface particle motion, precision reliability which arrivals can be identified, aid detailed study near-station effects signals. Results rotation apparent coordinates longitudinal horizontal, transverse vertical; multiplication vertical components; integration product serve as examples transformation. seismograms digitized any desired, using relatively simple, automatic, low-speed digitizer (two 3-decimal digit readings per second).