Chinnery's model for a strike slip fault (1961)

For this first example we take M.A. Chinnery's model for a strike slip fault (see Figure below) and show you how to set up the input file, solve the boundary-value problem, and reproduce the figures in his two papers (and more!) in a just a few minutes, while gaining the improved perspective of 3D manipulation and visualization of the output. Chinnery concluded his now classic paper on “The Deformation of the Ground around Surface Faults” (B.S.S.A., 1961, v. 51, p. 355-372) with a remark that has proved both correct and understated:

“The most important conclusion to be deduced from the above discussion is that the mathematical concept of a dislocation surface appears to be applicable to the study of fracture of the earth’s crust. The agreement between theory and observation is not perfect, but the discrepancies are considered to be due only to the simplifying assumptions of the model, and the general features of the observed displacements agree well with those predicted.”

This paper and the companion paper by Chinnery on “The Stress Changes that Accompany Strike-slip Faulting’ (B.S.S.A., 1963, v. 53, p. 921-932) utilize J. A. Steketee’s results (1958a,b) for a rectangular dislocation in an elastic half-space and represented remarkable computational efforts and physical insights for their day.

The coordinate axes (y1, y2, y3) are specified as (X, Y, Z) in Poly3DGUI. Following Chinnery we take Lame’s constants as equal, λ = µ = 30 GPa, implying Poisson’s ratio ν = 0.25;, and Young’s modulus E = 75 GPa. The displacement, u, is normalized by the total displacement discontinuity, U. Lengths are normalized by the half-length, L, of the model fault which is square, D/L = 2, and the depth, d, to the top of the fault is taken as zero.