Abstract
A variety of geophysical observations suggests that the upper portion of the lithosphere, herein referred to as the elastic plate, has long-term material properties and frictional strength significantly greater than the lower lithosphere. If the average frictional stress along the non-ridge margin of the elastic plate is of the order of a kilobar, as suggested by the many observations of the frictional strength of rocks at mid-crustal conditions of pressure and temperature, the only viable mechanism for driving the motion of the elastic plate is a basal shear stress of several tens of bars. Kilobars of tectonic stress are then an ambient, steady condition of the earth's crust and uppermost mantle. The approximate equality of the basal shear stress and the average crustal earthquake stress drop, the localization of strain release for major plate margin earthquakes, and the rough equivalence of plate margin slip rates and gross plate motion rates suggest that the stress drops of major plate margin earthquakes are controlled by the elastic release of the basal shear stress in the vicinity of the plate margin, despite the existence of kilobars of tectonic stress existing across vertical planes parallel to the plate margin. If the stress differences available to be released at the time of faulting are distributed in a random, white fasbion with a mean-square value determined by the average earthquake stress drop, the frequency of occurrence of constant stress drop earthquakes will be proportional to reciprocal faulting area, in accordance with empirically known frequency of occurrence statistics.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Aki, K. (1972),Earthquake mechanism, Tectonophysics13, 423–446.
Andrews, D. J. (1972),Numerical simulation of sea-floor spreading, J. Geophys. Res.77, 6470–6481.
Brace, W. F. (1972),Laboratory studies of stick-slip and their application to earthquakes, Tectonophysics14, 189–200.
Brace, W. F., andByerlee, J. D. (1970),California earthquakes: why only shallow focus? Science168, 1573–1575.
Brune, J. N. (1968),Seismic moment, seismicity, and rate of slip along major fault zones J. Geophys. Res.73, 777–784.
Brune, J. N. (1970),Tectonic stress and the spectra of seismic shear waves, J. Geophys. Res.75, 4997–5009.
Brune, J. N. (1971),Correction, J. Geophys. Res.76, 5002.
Brune, J. N., Henyey, T. L. andRoy, R. F. (1969),Heat flow, stress, and rate of slip along the San Andreas fault, California, J. Geophys. Res.74, 3821–3827.
Burdick, L. J. andMellman, G. R. (1976),Inversion of the body waves from the Borrego Mountain earthquake to the source mechanism, Bull. Seismol. Soc. Amer.66, 1485–1499.
Byerly, P. andDe Noyer, J.,Energy in earthquakes as computed from geodetic observations inContributions in Geophysics in Honor of Beno Gutenberg (Pergamon Press, New York, 1958).
Caldwell, J., Hixby, W. F., Karig, D. E. andTurcotte, D. L. (1976),On the applicability of a universal elastic trench profile, Earth Plan. Sci. Lett.31, 239–246.
Carter, N. L. (1976),Steady state flow of rocks, Rev. Geophys. Space Phys.14, 301–360.
Chinnery, M. A. (1961),The deformation of the ground around surface faults, Bull. Seismol. Soc. Amer.51, 355–372.
Chinnery, M. A. (1964),The strength of the Earth's crust under horizontal shear stress. J. Geophys. Res.69, 2085–2089.
Davies, G. F. andBrune, J. N. (1971),Regional and global fault slip rates from seismicity, Nature229, 101–107.
Ellsworth, W. L., Campbell, R. H., Hill, D. P., Page, R. A., Alewine, R. W., Hanks, T. C., Heaton, T. H., Hileman, J. A., Kanamori, H., Minster, B. andWhitcomb, J. H. (1973),Point Mugu, Caltfornia, earthquake of 21 February 1973 and its aftershocks Science182, 1127–1129.
Forsyth, D. W. (1977),The evolution of the upper mantle beneath mid-ocean ridges Tectonophysics, in press.
Forsyth, D. andUyeda, S. (1975),On the relative importance of the driving forces of plate motion, Geophys. J. Roy. Astron. Soc.43, 163–200.
Hanks, T. C. (1971),The Kuril trench-Hokkaido rise system: large shallow earthquakes and simple models of deformation, Geophys. J. Roy. Astron. Soc.23, 173–190.
Hanks, T. C. (1974),The faulting mechanism of the San Fernando earthquake, J. Geophys. Res.79, 1215–1229.
Hanks, T. C. andJohnson, D. A. (1976),Geophysical assessment of peak accelerations Bull. Seismol. Soc. Amer.66, 959–968.
Hanks, T. C. andWyss, M. (1972),The use of body-wave spectra in the determination of seismic source parameters, Bull. Seismol. Soc. Amer.62, 561–590.
Jeffreys, H.,The Earth (Cambridge University Press, Cambridge, 1959).
Kanamori, H. andAnderson, D. L. (1975),Theoretical basis of some empirical relations in seismology, Bull. Seismol. Soc. Amer.65, 1073–1096.
Kanamori, H. andPress, F. (1970),How thick is the lithosphere? Nature226, 330–331.
Hasahara, K. (1987),The nature of seismic origins as inferred from seismological and geodetic observations (1), Bull. Earthquake Res. Inst. Tokyo Univ.,35, 475–532.
Kirby, S. (1977),State of stress in the lithosphere: inferences from the flow laws of olivine, Pure appl. Phys.115, 245–258.
Lachenbruch, A. H. andSass, J. H.,Thermo-mechanical aspects of the San Andreas fault system inProceedings of the Conference on Tectonic Problems of the San Andreas fault system (eds. R. L. Kovach and A. Nur) (Stanford University Publications, Stanford 1973), pp. 192–205.
McKenzie, D. P. (1969),Some remarks on heat flow and gravity anomalies, J. Geophys. Res.72, 6261–6273.
McKenzie, D. P. (1969),Speculations on the consequences and causes of plate motions, Geophys. J. Roy. Astron. Soc.18, 1–32.
Molnar, P. andWyss, M. (1972),Moments, source dimensions and stress drops of shallow-focus earthquakes in the Tonga-Kermadec arc, Phys. Earth Planet. Interiors6, 263–278.
Nakamura, K. andJacob, K. (1976),Volcanoes as indicators of tectonic stress orientation-Aleutians and Alaska (abs.), EOS57, 1006.
Parsons, B. andMolnar, P. (1976),The origin of outer topographic rises associated with trenches Geophys. J. Roy. Astron. Soc.45, 707–712.
Savage, J. C. andBurford, R. O. (1973),Geodetic determination of relative plate motion in central California, J. Geophys. Res.78, 832–845.
Sclater, J. G. andFrancheteau, J. (1970),The implications of terrestrial heat flow observations on current tectonic and geochemical models of the crust and upper mantle of the earth, Geophys. J. Roy. Astron. Soc.20, 509–542.
Solomon, S. C., Sleep, N. H. andRichardson, R. M. (1975),On the forces driving plate tectonics: inferences from absolute plate velocities and intraplate stress, Geophys. J. Roy. Astron. Soc.42, 769–801.
Stesky, R. M. andBrace, W. F.,Estimation of frictional stress on the San Andreas fault from laboratory measurements inProceedings of the Conference on Tectonic Problems of the San Andreas fault system (eds. R. L. Kovach and A. Nur) (Stanford University Publications, Stanford, 1973), pp. 206–214.
Thatcher, W. (1972),Regional variations of seismic source parameters in the northern Baja California area, J. Geophys. Res.77, 1549–1565.
Thatcher, W. (1975),Strain accumulation and release mechanism of the 1906 San Francisco earthquake, J. Geophys. Res.80, 4862–4872.
Thatcher, W. andHamilton, R. M. (1973),Aftershocks and source characteristics of the 1969 Coyote Mountain earthquake, San Jacinto fault zone, California, Bull. Seismol. Soc. Amer.63, 647–661.
Thatcher, W. andHanks, T. C. (1973),Source parameters of southern California earthquakes, J. Geophys. Res.78, 8547–8576.
Tucker, B. E. andBrune, J. N.,Seismograms, S-wave spectra, and source parameters for aftershocks of San Fernando earthquake inSan Fernando, California Earthquake of February 9, 1971, Vol. III (Geological and Geophysical Studies, 69–122, U.S. Dept. of Commerce, 1973).
Watts, A. B. andTalwani, M. (1974),Gravity anomalies seaward of deep-sea trenches and their tectonic implications, Geophys. J. Roy. Astron. Soc.36, 57–90.
Wyss, M. andHanks, T. C. (1972),The source parameters of the San Fernando earthquake inferred from teleseismic body waves, Bull. Seismol. Soc. Amer.62, 591–602.
Wyss, M. andMolnar, P. (1972),Source parameters of intermediate and deep focus eurthquakes in the Tonga arc, Phys. Earth Planet. Interiors6, 279–292.
Zoback, M. D. andByerlee, J. D. (1976)A note on the deformational behavior and permeability of crushed granite, Int. J. Rock Mech. Min. Sci. Geomech. Abstr.13, 291–294.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Hanks, T.C. Earthquake stress drops, ambient tectonic stresses and stresses that drive plate motions. PAGEOPH 115, 441–458 (1977). https://doi.org/10.1007/BF01637120
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF01637120