A study of blasting recorded in Southern California

Abstract

Seismographic registration of vibratory earth motion was begun with an experimental torsion seismometer assembly at the laboratories of the Mount Wilson Observatory in Pasadena, California, in January, 1923. Not long afterward a second assembly was put into experimental operation at the Norman Bridge Laboratory of Physics at the California Institute of Technology at Pasadena. With many small, experimental changes in design and adjustment, which led to change in constants and necessitated some interruptions, recording on an experimental basis continued for more than four years. However, in October, 1926, recording was begun with equipment of more permanent form at Riverside and, after a short time, at the Seismological Laboratory at Pasadena in March, 1927, and at Santa Barbara and at La Jolla in May, 1927. After the occupation of the Seismological Laboratory, the experimental recording at the laboratories of the Mount Wilson Observatory and at the Norman Bridge Laboratory of Physics was brought to a close in the course of a few months. In April, 1928, recording was begun at the Observatory on Mount Wilson; and in September, 1929, at Tinemaha, and at Haiwee, in the Owens Valley, Inyo County, California. stations, and the heights above sea-level, are given in Table I.

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