Abstract

Summary
  1. A list of shocks which have occurred near Whittier, California, in recent years is given, with brief discussion. Field data are given in tabular form for the shocks of May 4, 1929; and on a map showing values of intensity for the shock of July 8, 1929, at 8h 46m 07s a.m., P.S.T. Aftershocks are discussed briefly.

  2. The data of registration for the main shock and for several aftershocks, especially that of November 3, 1930, are given. Phases registered were identified as P and S, and rectilinear propagation of the wave motion assumed. Without further assumption a value of the ratio of velocities VP/Vs was determined.

  3. A solution for the epicenter and depth of focus of the shock of November 3, 1930, at 10:19 a.m., was determined as follows: ϕ = 33° 54.9′ N., λ = 118° 01.9′ W., depth = h = 13.1 kilometers (8+ miles), with corresponding velocities VP = 5.55 kilometers per second, VS = 3.25 kilometers per second.

  4. A third conspicuous phase was identified on the seismograms as S24S, a transversal wave reflected at a depth of about 24 kilometers (15— miles).

  5. On the basis of aftershock data, together with data for the main shock, an epicenter and depth of focus for the latter was approximated, and a corresponding origin-time adopted, as follows: ϕ = 33° 54.8′ N., λ = 118° 02.4′ W., depth = h = 13 kilometers (8+ miles), and O = 8h 46m 07s a.m., P.S.T. = 16h 46m 07sG.C.T., July 8, 1929

  6. A transmission-time diagram is given on the basis of the data of the main shock, together with that of certain aftershocks.

  7. Alternative interpretations of the phases identified as P, S, and S24S are discussed.

  8. The geological conditions and the probable nature of the material traversed by the waves is discussed.

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