On Seismic Waves (Third Paper)

In two previous papers under the present title 1) 2) the authors have presented data on bodily waves. The present paper contains the corresponding data on surface waves (including seismic sea waves), the magnitude and energy of earthquakes, and miscellaneous topics. The seismograms used were those studied in the previously published investigations; the numbers assigned to individual shocks are as given in the previous papers

On Seismic Waves (Second Paper)

In a first paper under the present title the authors have presented a body of data on travel times. The present paper contains the corresponding data on amplitudes, periods, velocities, etc., for bodily waves. It is intended to present data on surface waves in a third paper

Body waves in inhomogeneous media

Several investigators have demonstrated that in anisotropic media there are three types of waves. For a long time, I have suspected that it is also possible to demonstrate the existence of three types of propagation in inhomogeneous media which are isotropic. I have not been able to do this in general, but only in certain special cases which, in themselves, have no seismological interest. Obviously, if three wave types exist in these special cases, then they must also be considered in the more general cases

Mathematical questions in seismology

Seismologists, like mathematicians, are accustomed to dividing their subject into a pure and an applied branch. The desirability of such division is underlined by the manner in which non-seismologists frequently approach the subject. It is too often taken for granted that, because an earthquake is a motion of the ground, seismology must be chiefly concerned with the detailed analysis of that motion for its own sake. Such analysis is important in the engineering section of applied seismology; but it is unrepresentative of seismology as a whole, which deals largely with more remote problems: the causative mechanism of earthquakes, the distribution of their origins geographically and in depth, or the structure and physical condition of the interior of the earth

Calculation of small distances

Tables are presented which facilitate the calculation of small distances between points on the earth's surface whose latitudes and longitudes are given, for mean latitudes from 30° to 40°. The error does not exceed one-tenth of a kilometer in 500 kilometers, and may be reduced by applying specified corrections

The Manix (California) earthquake of April 10, 1947

This report presents seismometric and field data, exclusive of those relating to geology and field evidence of faulting. It includes information reaching the Seismological Laboratory at Pasadena from various sources and embodies the results of investigation by members of the Laboratory staff, and by other staff members and students of the Division of the Geological Sciences, California Institute of Technology. All times mentioned are Pacific Standard Time

The Alaskan Earthquake

Caltech's Seismological Laboratory goes to work on The Alaskan Earthquake

Velocities of P at short distances

Recording of P and S at six or more stations to epicentral distances not over 160 km. makes it possible to calculate the velocities, assuming only that they are constant. Origin times, epicenters, and depths are found independently of velocity. Installation of new temporary stations has supplied appropriate data in southern California. For 6 of 8 well-recorded shocks the calculated velocity of P is near 6.4 km/sec