SCEC Stress-triggering & Deformation Software Training

This two-day course will introduce participants in hands-on sessions to three software codes in current use for studies of earthquake and fault interaction: Coulomb 1.0 (S. Toda, G. King, & R. Stein); 3D-DEF (M. Ellis & J. Gomberg), and VISCO1D (F. Pollitz). Everyone is welcome, students and senior researchers, geologists and seismologists alike. Each code will be presented by its authors, who will walk participants through tutorials and provide simple manuals. All codes and manuals will be available electronically. The goal is for the participants to develop sufficient skill that they will use the codes in their own research, and teach them to others.

About the workshop:

To give everyone keyboard/monitor access, we can accommodate only 45 people.We will be housed in suites at the Schwab Residential Center of the Stanford Business School; instruction will take place a 15-minute walk away at the Mitchell Earth Sciences 20-station training center. People will arrive Tuesday afternoon, Sept 7. There will be a welcoming reception Tuesday evening, a BBQ on Wednesday evening, and an afternoon run on the beautiful 'dish hill.' People will return to the airport Thursday evening at about 6 pm with new skills and confidence. SCEC will cover tuition, within-CA airfare, airport van shuttle, meals and accommodations for its members.

About the software:

Coulomb 1.0 was principally written by Shinji Toda (ERI, Japan, it is an evolution of GEN 1.0 by Geof King (IPG, Paris). Coulomb is a fast, menu-driven Mac program rich in graphics. It performs 3D elastic dislocation and a limited number of 2D boundary element calculations of deformation and stress in an elastic halfspace. It can input fault slip and focal mechanism files, and can output displacements, optimally-oriented Coulomb stress changes and resolved stress changes at any depth on any surface in a Cartesian x,y,z coordinate system. It will be taught by Shinji Toda and Ross
Stein.

3D-DEF was written by Joan Gomberg (USGS, Memphis) and Michael Ellis (CERI, Univ. Memphis), and performs elastic dislocation boundary-element calculations. Boundary elements permit one to examine, for example, how a fault will slip in response to applied stresses. Unlike finite element codes, little or no gridding is needed. The program enables a variety of boundary conditions to be applied, which makes the model quite flexible. It is supplemented by a limited number of simple Matlab routines that enabl graphic visualizations of results. 3D-DEF is a stand-alone program built around the Okada (1992) Green's functions, and runs on any computer with a fortran compiler. All input and output is in ascii files. The program and manual can be obtained via anonymous ftp to beagle.ceri.memphis.edu in /pub/gomberg. It will be taught by Ellis and Gomberg.

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. It will be taught by Pollitz.

Interested people should contact Nancy Sandoval by JUNE 8 at nsandoval@usgs.gov (tel 1 650 329 4883; fax 1 650 329 4876). After June 8, email Ross Stein at rstein@usgs.gov to see if places are available. Please indicate what s/w below interests you, so we can plan the sessions accordingly.