HORIZONTAL SURFACE DEFORMATION DUE TO DIKE EMPLACEMENT IN AN ELASTIC-GRAVITATIONAL LAYER OVERLYING A VISCOELASTIC-GRAVITATIONAL HALF-SPACE

We extend a technique previously used to model surface displacements resulting from thrust faulting in an elastic-gravitational layer over a viscoelastic-gravitational half-space to the case of dike emplacement. The method involves the calculation of the Green's functions for a dike point source contained in an elastic-gravitational layer over an elastic-gravitational half-space. The correspondence principle is then applied to introduce time dependence. The resultant Green's functions are integrated over the source region to obtain the near-field displacements. Several example calculations are presented involving 90 degrees, 60 degrees, and 30 degrees dipping dikes, extending completely and partially through the elastic layer. We also illustrate the time dependent deformation due to buried dikes. Dikes extending completely through the elastic layer produce a larger-amplitude long-wavelength component than those extending partially through the elastic layer. Inflexion points are seen in the dike-normal horizontal deformation profiles when the base of the dike intersects the top of the half-space, providing a means of differentiating between vertical surface dikes extending completely and partially through the elastic layer. All results show that the use of a viscoelastic half-space underlying an elastic layer introduces a long-wavelength component into the deformation field that cannot be predicted by elastic half-space models.