BACKGROUND NOISE ON THE S. S. S. STANDARD INSTRUMENTS (RUIDO DE FONDO EN LOS SISMOGRAFOS STANDARD DEL SERVICIO DE SISMOLOGIA)

A study of noise observed on the Toledo and Malaga seismographs of the World-wide Standarized Seismograph Network is given. For both sets of instruments, LP and SP, the noise is classified in microseisms and disturbances. The spectrum of LP and SP microseisms is obtained and compared with previous d...

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Bibliographic Details
Main Author: Arroyo,A Lopez
Format: Report
Language:English
Subjects:
BACKGROUND
CALIBRATION
DETECTION
EARTHQUAKES
MICROSEISMS
NOISE
Seismic Detection and Detectors
SEISMOGRAPHS
SEISMOLOGICAL STATIONS
Seismology
SPAIN
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Summary:A study of noise observed on the Toledo and Malaga seismographs of the World-wide Standarized Seismograph Network is given. For both sets of instruments, LP and SP, the noise is classified in microseisms and disturbances. The spectrum of LP and SP microseisms is obtained and compared with previous data. A minimum of the amplitude in the neighborhood of 2 cps, already observed at many sites of the USA, is also shown for Toledo and Malaga; whereas the maximum of the spectrum around 4 - 8 sec, established by Brune and Oliver and considered by them as a major result of observational seismology is not clearly defined. Annual variation of microseismic period and amplitude is analyzed and the ratio AH/AZ derived; such ratio is used for computing the thickness of the sedimentary layer at the observatories. Observation shows the existence of a predominant period of microseisms at the two places considered. The data include periods greater than 0.4 sec only, since the instruments are not sensitive enough for recording shorter period microseisms; but they show a clear distinction between the period distribution curves of Toledo and Malaga, which is explained in terms of difference in geologic structure. LP disturbances are correlated with wind and movement of people inside the Observatory. A very near origin (inside the vault, perhaps in the seismometer) is suggested for pulses observed on the three LP components. SP disturbances, on the other hand, are seen to be produced partly by traffic along nearby road. (Author)