The results of two previous papers by Chinnery published in 1963 and 1964 are used to calculate the distribution of stress that is present after the formation of a strike-slip fault. The pattern obtained shows that although the initial stress is reduced over most of the length of the fault, there are strong concentrations of shear stress near the ends. It is therefore suggested that secondary faulting is due to these end effects, and patterns of likely modes of secondary faulting are shown. The geological implications of these results are discussed in another paper, on the geological aspects of Secondary faulting.

Recent theoretical expressions for the change in stress distribution caused by strike‐slip faulting are applied to five real faults, and estimates are made of the maximum shear stress relieved in each case. The calculated values lie between 107 and 108 dynes/cm2, and reasonable refinements of the assumptions involved in the calculation (particularly in the value of the coefficient of rigidity) all tend to reduce these estimates, perhaps by an order of magnitude. A discussion of the mechanism of faulting suggests that the stress change is unlikely to differ by more than a factor of 2 from the shear stress that caused the fracture. It is concluded that the strength of the earth's crust under horizonal shear stress appears to be little more than 107 dynes/cm2 and may be less in some areas.

This paper is the first of a series that will examine the effect of earth structure on earthquake displacement, strain and tilt fields at the Earth's surface. Its purpose is to develop the numerical techniques to be applied in the papers that foliow. A general computational procedure for the evaluation of the integral expressions for the surface displacements due to an arbitrary point dislocation source in a layered medium is described. It is shown to be rapid and inexpensive to use, and its accuracy appears to be entirely adequate for practical purposes.

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There has been a considerable amount of confusion in the literature concerning the formulation of the problem of the static deformation of an Earth model with a fluid core. Dahlen has recently discussed this problem using an Eulerian description of motion in the core. This paper outlines a physical approach to the problem, using Lagrangian variables throughout, where deformation in the mantle is described in terms of particle dispiacements and deformation in the core is described in terms of bulk fluid properties (density, pressure and gravitational potential). This approach clarifies Longman's paradox and the nature of the boundary conditions at the core-mantle boundary.