Abstract
A theory is proposed about the strain in the earth's crust due to the periodic (annual or daily) variation of surface temperature.
From the equations of heat-conduction and of motion in thermoelastic solid the exact solution is firstly given in integral form, whose approximate expression is then derived, by taking account of the magnitudes of physical constants. Particularly, about the surface temperature with amplitude varying discontinuously at a point, the fields of strain and temperature are explicitly obtained by the method of steepest descent. The solution can be extended to the case that the amplitude varies continuously in an interval. It is pointed out that the strain is separated into two terms, one of which, though having a large amplitude in shallow range, rapidly attenuates with depth, while the other is slow to attenuate, with a small amplitude from the first.
The former is regarded as the strain due to heat-energy conducted to the point of observation and the latter is purely an elastic deformation propagating as body-waves from the discontinuous point. Comparison with the observed results confirms this separation of strain, to some extent.
