Regional seismicity and seismic wave propagation from records at the Tonto Forest Seismological Observatory, Payson, Arizona

s. j. duda


The records of the Tonto Forest Seismological Ohservatorynear Payson, Arizona, have been used to investigate the applicabilityof an array station for the study of locai seismicity and seismic wave propagationat short epicentral distances. Inferences are drawn about theseismicity of Arizona and the characteristics are given for two earthquakesequences, in Imperiai County, California, and in Baja California.The records of the earthquakes and a selection of quarry blasts areused for the study of the propagation of crustal waves. According to theirgroup velocities and appearance, the Sg and P*-waves observed at smallepicentral distances are identical with the Lg2 and jzj-wave respectively,observed at larger epicentral distances.The ratio of S to P wave energy is estimated to be of the order of100 : 1 for earthquakes at an epicentral distance of about 14 km. Theattenuation of Sjr-wave energy has a discontinuity at an epicentral distanceof 325 km and possibly another at 100 km. Because of this fact an appreciabledifference of seismic energies recorded at two epicentral distances,slightly below and above these criticai distances, will be observed. Theduration of the iSjf-phase depends mainly on the magnitude of the earthquakes.

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X