HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) References Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by GUPTA, I. N. Search for Related Content GeoRef GeoRef Citation

Premonitory changes in t_s/t_p due to anisotropy and migration of hypocenters

MACKAY SCHOOL OF MINES UNIVERSITY OF NEVADA, RENO, NEVADA 89507

Abstract

The anisotropic characteristics of stress-induced cracks in dilatant rock can significantly influence the observed values of t_s/t_p obtained using the Wadati diagram. Systematic vertical migration of hypocenters of foreshocks within a region of thrust tectonics can lead to variations in both t_s/t_p and orientation of the compressive stress axis of the same type as observed before several thrust-type earthquakes. In this model, the seismic velocities become considerably anisotropic due to preferential alignment of open cracks, but it is not essential to assume pre-earthquake flow of groundwater into the dilated zone. Observations of t_s/t_p versus depth of focus in the Garm region, USSR and some other results appear to support this possibility.

Footnotes

^* Present address: Dames & Moore, 1550 Northwest Highway, Park Ridge, Illinois 60068.

This article has been cited by other articles:

				J. A. STEPPE, W. H. BAKUN, and C. G. BUFE Temporal stability of P-velocity anisotropy before earthquakes in central California Bulletin of the Seismological Society of America, August 1, 1977; 67(4): 1075 - 1090. [Abstract] [PDF]