Open AccessA Study of the Magnitude Difference M s — m b for Earthquakes
Author(s) -
Prozorov A.,
Hudson J. A.
Publication year - 1974
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1974.tb05472.x
Subject(s) - magnitude (astronomy) , amplitude , geology , seismology , geodesy , earthquake magnitude , physics , mathematics , geometry , optics , astrophysics , scaling
Summary The amplitude ratio of surface and body waves generated by a sample of over 1000 earthquakes is studied on the basis of the values of R = M s — m b . By considering first of all, only those events with m b between 5 and 6, the dependence of R on magnitude is practically eliminated. It is found that R depends on depth of focus to a smaller degree than expected but that it varies significantly from one region to another (e.g. from Southern to Northern Pacific). It appears that this variation has little to do with propagation path and is more likely reflecting a difference in conditions at the source. The correlation between R and ‘positive influence’ has also been investigated. This leads to the conclusion that high values of R are associated with heterogeneous source regions, low stress drop, and a slow speed of fracture process; thus giving rise to preferential generation of long periods.