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Stress is a measure of the amount of force exerted over an area. This stress intensity has units of force/(length squared) or N/m2 called Pascal (Pa) in SI units. Stress is the set of forces acting on the surfaces of a volume element. The relative and absolute magnitude and the orientations of stress varies over time and by location. If it exceeds the strength of the rock, then acceleration, translation, rotation, and strain can occur.


This interplay between rock strength, rock deformation mechanism, and stress determines the formation and displacement across fractures that can create earthquakes or host fluid flow.

LINKS


Resources

  1. World Stress Map


Tools

  1. Coulomb3

  2. Poly3D

  3. ALT Wellcad

  4. GMI Imager

WHAT IS STRESS?

Map of the Coso Geothermal Field including stresses inferred using different methods, active faults, and geothermal alteration. On average the least principal horizontal stress has a consistent orientation across the geothermal field. Small perturbations occur very close to faults and also over short depth intervals (not shown).

Stress model of the Coso Geothermal Field. Stress magnitudes increase with increasing depth. Measured magnitudes of differential stress are within the limits predicted by frictional faulting with geologically reasonable coefficients of static friction.

Slip tendency of faults in the Coso Geothermal Field inferred from the stress model.

MEASURING STRESS IN THE SHALLOW CRUST

© Nicholas C. Davatzes

Last Updated: 2008/12