Name of program: VISCO1D

Type of program (eg quake model, mesh generator, strain calculator, visualizer, etc): viscoelastic spherical deformation due to faulting or dike emplacement

Author: Fred Pollitz (UCD)

VISCO1D, written by Fred Pollitz (UCD) calculates the response of a spherically stratified elastic-viscoelastic medium to the stresses generated by fault slip or dike opening occurring in one of the elastic layers. The response is in terms of a spherical harmonic expansion of spheroidal and toroidal motion components, each component representing one mode of relaxation with its own characteristic decay time and spatial deformation pattern. It is flexible, allowing the determination of time-dependent postseismic deformation fields (displacement and strain) at any depth level. Its main parts are: (1) Specification of a stratified Earth model (elastic modulii and viscosity of each layer); (2) Identification of spheroidal and toroidal motion modes, consisting of a set of characteristic decay times for each spherical harmonic degree; (3) Determination of the corresponding displacement-stress vectors for each of these modes; and (4) Determination of postseismic deformation at specified times, observation points (lat, lon, depth), and source geometry and slip. There is a fast version for non-gravitational viscoelastic response, and another for gravitational viscoelastic response.