Open AccessTwo‐dimensional ground motion at a soft viscoelastic layer/hard substratum site in response to SH cylindrical seismic waves radiated by deep and shallow line sources—II. Numerical results
Author(s) -
Groby JeanPhilippe,
Wirgin Armand
Publication year - 2005
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2005.02713.x
Subject(s) - seismogram , viscoelasticity , geology , line source , boundary (topology) , line (geometry) , mechanics , seismology , geometry , physics , acoustics , mathematics , mathematical analysis , thermodynamics
SUMMARY We consider, using theory and associated synthetic seismograms, the seismic response of a site comprising a horizontal, homogeneous, soft viscoelastic layer of infinite lateral extent overlying, and in welded contact with, a homogeneous, hard elastic substratum of half‐infinite radial extent. We show that for shear‐horizontal motion: (1) coupling to Love modes is all the weaker the deeper the source (modelled as a line, assumed to lie in the substratum) is from the lower boundary of the soft layer, (2) for a line source close to the lower boundary of the soft layer, the ground response is characterized by possible beating phenomena, and is of significantly longer duration than for excitation by cylindrical waves radiated by deep sources. Numerical applications of the theory show, for instance, that a line source, located 40 m below the lower boundary of a 60‐m‐thick soft layer in a hypothetical Mexico‐City‐like site, radiating a SH pulse of 4 s duration, produces substantial ground motion during 200 s, with marked beating, at an epicentral distance of 3 km. Results from this modelling study are supported by field examples taken from published literature.