pure and applied geophysics

, Volume 142, Issue 3, pp 467–489

Some comparisons between mining-induced and laboratory earthquakes

  • A. McGarr
Earthquake Source Mechanics and Fracture Mechanics: Theory and Observation

DOI: 10.1007/BF00876051

Cite this article as:
McGarr, A. PAGEOPH (1994) 142: 467. doi:10.1007/BF00876051


Although laboratory stick-slip friction experiments have long been regarded as analogs to natural crustal earthquakes, the potential use of laboratory results for understanding the earthquake source mechanism has not been fully exploited because of essential difficulties in relating seismographic data to measurements made in the controlled laboratory environment. Mining-induced earthquakes, however, provide a means of calibrating the seismic data in terms of laboratory results because, in contrast to natural earthquakes, the causative forces as well as the hypocentral conditions are known. A comparison of stick-slip friction events in a large granite sample with mining-induced earthquakes in South Africa and Canada indicates both similarities and differences between the two phenomena. The physics of unstable fault slip appears to be largely the same for both types of events. For example, both laboratory and mining-induced earthquakes have very low seismic efficiencies\(\eta = \tau _a /\bar \tau\) where τa is the apparent stress and\(\bar \tau\) is the average stress acting on the fault plane to cause slip; nearly all of the energy released by faulting is consumed in overcoming friction. In more detail, the mining-induced earthquakes differ from the laboratory events in the behavior of η as a function of seismic momentM0. Whereas for the laboratory events η≃0.06 independent ofM0, η depends quite strongly onM0 for each set of induced earthquakes, with 0.06 serving, apparently, as an upper bound. It seems most likely that this observed scaling difference is due to variations in slip distribution over the fault plane. In the laboratory, a stick-slip event entails homogeneous slip over a fault of fixed area. For each set of induced earthquakes, the fault area appears to be approximately fixed but the slip is inhomogeneous due presumably to barriers (zones of no slip) distributed over the fault plane; at constant\(\bar \tau\), larger events correspond to largerτa as a consequence of fewer barriers to slip. If the inequality τa/\(\bar \tau\) ≤ 0.06 has general validity, then measurements of τaEa/M0, where μ is the modulus of rigidity andEa is the seismically-radiated energy, can be used to infer the absolute level of deviatoric stress at the hypocenter.

Key words

Stick-slip frictionmining-induced earthquakesseismic efficiency

Copyright information

© Birkhäuser Verlag 1994

Authors and Affiliations

  • A. McGarr
    • 1
  1. 1.U.S. Geological SurveyMenlo ParkUSA