The California Earthquake of April 18, 1906: Report of the State Earthquake Investigation Commission ...

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Carnegie Institution of Washington, 1910 - Earthquakes
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Page 29 - ... we conclude that the crust, in many parts of the earth, is being slowly displaced, and the difference between displacements in neighboring regions sets up elastic strains, which may become greater than the rock can endure ; a rupture then takes place and the strained rock rebounds under its own elastic stresses until the strain is largely or wholly relieved.
Page 39 - The more or less sudden stopping of the movement and the friction gives rise to the vibrations which are propagated to a distance. The sudden starting of the motion would produce vibrations just as would its sudden stopping, and vibrations are set up by the friction of the moving rock just as the vibrations of a violin string are caused by the friction of the bow.
Page 13 - A perfectly diffusing surface is one for which the luminous intensity per unit area in any direction varies as the cosine of the angle between that direction and the normal to the surface, so that it appears equally bright whatever be the direction from which it is viewed.
Page 29 - It is impossible for rock to rupture without first being subjected to elastic strains greater than it can endure. We conclude that the crust in many parts of the earth is being slowly displaced and the difference between displacements in neighboring regions sets up elastic strains, which may become larger than the rock can endure. A rupture then takes place and the then strained rock rebounds under its own elastic stresses, until the strain is largely or wholly relieved.
Page 31 - Great uplifts have occurred unaccompanied by compressions, due, apparently, to vertical forces; and the California earthquake has emphasized the existence of horizontal drags below the crust. Future study may reveal forces applied in other ways; but it is not going too far to say that whenever ruptures occur, they result from elastic strain, and the sudden movements produced are merely elastic rebounds; and moreover, except in the case of earthquakes connected directly with volcanic action, the strains...
Page 3 - ... entry. I remember distinctly getting the minute-hand's position, previous to the most violent portion of the shock. The end of the shock I did not get exactly, as I was watching the second-hand and the end came several seconds before I fully took in the fact that the motion had ceased.
Page 19 - two.thirds of the stress which caused the rupture had already accumulated 25 years ago," and that "50 years ago the elastic strain, which caused the rupture in 1906, had already accumulated to nearly half its final amount. It seems not improbable, therefore, that the strain was accumulating for 100 years, altho there is no satisfactory reason to suppose that it accumulated at a uniform rate.
Page 3 - ... San Francisco, California, 1906 shock has been described in "The California Earthquake of April 18, 1906," (Report of the State Earthquake Investigation Commission, in vol. 2, pp. 3-5, 1910) . This report states "that the earthquake began with a fairly strong movement which continued increasing in strength for an interval variously estimated, but which really amounted to about half a minute; then very violent shocks occurred, and quiet was restored about 3 minutes later.
Page 197 - This volume is for in-library use only. It may not be charged out. Return this book on or before date due.
Page 137 - ... the cosine of the angle between the direction of propagation and the vertical axis z.