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Solid Earth An interactive open-access journal of the European Geosciences Union

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https://doi.org/10.5194/sed-2-105-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.
 
12 Apr 2010
Review status
This discussion paper has been under review for the journal Solid Earth (SE). The revised manuscript was not accepted.
The mechanics of gravity-driven faulting
L. Barrows and V. Barrows private address: 103 Gilmore Circle, Covington, LA 70433, USA
Abstract. Faulting can result from either of two different mechanisms. These involve fundamentally different energetics. In elastic rebound, locked-in elastic strain energy is transformed into the earthquake (seismic waves plus work done in the fault zone). In force-driven faulting, the forces that create the stress on the fault supply work or energy to the faulting process. Half of this energy is transformed into the earthquake and half goes into an increase in locked-in elastic strain. In elastic rebound the locked-in elastic strain drives slip on the fault. In force-driven faulting it stops slip on the fault.

Tectonic stress is reasonably attributed to gravity acting on topography and the Earth's lateral density variations. This includes the thermal convection that ultimately drives plate tectonics. Mechanical analysis has shown the intensity of the gravitational tectonic stress that is associated with the regional topography and lateral density variations that actually exist is comparable with the stress drops that are commonly associated with tectonic earthquakes; both are in the range of tens of bar to several hundred bar.

The gravity collapse seismic mechanism assumes the fault fails and slips in direct response to the gravitational tectonic stress. Gravity collapse is an example of force-driven faulting. In the simplest case, energy that is released from the gravitational potential of the stress-causing topography and lateral density variations is equally split between the earthquake and the increase in locked-in elastic strain.

The release of gravitational potential energy requires a change in the Earth's density distribution. Gravitational body forces are solely dependent on density so a change in the density distribution requires a change in the body forces. This implies the existence of volumetric body-force displacements. The volumetric body-force displacements are in addition to displacements generated by slip on the fault. They must exist if gravity participates in the energetics of the faulting process.

From the perspective of gravitational tectonics, the gravity collapse mechanism is direct and simple. The related mechanics are more subtle. If gravity is not deliberately and explicitly included in an earthquake model, then gravity is locked out of the energetics of the model. The earthquake model (but not necessarily the physical reality) is then elastic rebound.


Citation: Barrows, L. and Barrows, V.: The mechanics of gravity-driven faulting, Solid Earth Discuss., 2, 105-144, https://doi.org/10.5194/sed-2-105-2010, 2010.
L. Barrows and V. Barrows
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version      Supplement - Supplement
 
RC C38: 'Review', Anonymous Referee #1, 11 Jun 2010 Printer-friendly Version Supplement 
 
RC C49: 'report', Anonymous Referee #2, 21 Jul 2010 Printer-friendly Version 
 
AC C59: 'Reply to referee comments', Vincent Barrows, 16 Aug 2010 Printer-friendly Version 
L. Barrows and V. Barrows
L. Barrows and V. Barrows

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