HR: 1330h
AN: S42C-0192    [PDF]
TI: The Energetics of Gravity Driven Faulting
AU: * Barrows, L
EM: lbarrows@andrews-eng.com
AF: Andrews Environmental Engineering, 3535 Mayflower Blvd., Springfield, IL 62707 United States
AB: Tectonic stress is reasonable attributed to gravity acting on the earth's density structures. The gravity collapse seismic mechanism assumes the earthquake fault fails and slips in direct response to the gravitational tectonic stress. Gravity collapse is simple but it involves some unusual energetics. In particular, gravitational potential energy is released from the stress-causing density structures. This energy is split between the seismic wave energy and an increase in locked-in elastic strain energy. In classic elastic rebound, the change in the locked-in elastic strain field drives slip on the fault. In gravity driven faulting, it stops slip on the fault. A change in gravitational potential energy implies a change in the density structure. The gravitational body force is directly dependent on density so a change in the density structure implies a change in the body force field. If the body force field changes, there must be volumetric body-force displacements. These are in addition to the displacements generated by slip on the fault surface. Their nature and significance remain largely unexplored. The gravity collapse mechanism provides a simple explanation for the occurrence of deep focus earthquakes in temperature/pressure environments that preclude the gradual accumulation of locked-in elastic strain energy. It also accounts for the dual-plane character of some Wadati-Benioff zones, post-seismic regional displacements that resemble the co-seismic regional displacements, and induced tectonic activity at a distance from the epicentral region. To the extent that tectonic stress originates from gravity acting on the Earth's density structures, the gravity collapse mechanism is fundamentally simple. It does not require the creation of a locked-in elastic strain field prior to the earthquake.
DE: 7209 Earthquake dynamics and mechanics
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: 2003 Fall Meeting