dorsal/arxiv
View Schema2D ground motion at a soft viscoelastic layer/hard substratum site in response to SH cylindrical seismic waves radiated by deep and shallow line sources
| Authors | Armand Wirgin, J. -P. Groby |
|---|---|
| Categories | |
| ArXiv ID | physics/0401097 |
| URL | https://arxiv.org/abs/physics/0401097 |
Abstract
We show, essentially by theoretical means, that for a site with the chosen simple geometry and mechanical properties (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, shear-horizontal motion): 1) coupling to Love modes is all the weaker the farther the seismic source (modeled 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 40m below the lower boundary of a 60m thick soft layer in a hypothetical Mexico City-like site, radiating a SH pulse of 4s duration, produces substantial ground motion during 200s, with marked beating, at an epicentral distance of 3km. This response is in some respects similar to that observed in real cities located at soft-soil sites so that the model employed herein may help to establish the causes and pinpoint the major contributing factors of the devastating effects of earthquakes in such cities.
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"abstract": "We show, essentially by theoretical means, that for a site with the chosen\nsimple geometry and mechanical properties (horizontal, homogeneous, soft\nviscoelastic layer of infinite lateral extent overlying, and in welded contact\nwith, a homogeneous, hard elastic substratum of half-infinite radial extent,\nshear-horizontal motion): 1) coupling to Love modes is all the weaker the\nfarther the seismic source (modeled as a line, assumed to lie in the\nsubstratum) is from the lower boundary of the soft layer, 2) for a line source\nclose to the lower boundary of the soft layer, the ground response is\ncharacterized by possible beating phenomena, and is of significantly-longer\nduration than for excitation by cylindrical waves radiated by deep sources.\nNumerical applications of the theory show, for instance, that a line source,\nlocated 40m below the lower boundary of a 60m thick soft layer in a\nhypothetical Mexico City-like site, radiating a SH pulse of 4s duration,\nproduces substantial ground motion during 200s, with marked beating, at an\nepicentral distance of 3km. This response is in some respects similar to that\nobserved in real cities located at soft-soil sites so that the model employed\nherein may help to establish the causes and pinpoint the major contributing\nfactors of the devastating effects of earthquakes in such cities.",
"arxiv_id": "physics/0401097",
"authors": [
"Armand Wirgin",
"J. -P. Groby"
],
"categories": [
"physics.geo-ph"
],
"title": "2D ground motion at a soft viscoelastic layer/hard substratum site in response to SH cylindrical seismic waves radiated by deep and shallow line sources",
"url": "https://arxiv.org/abs/physics/0401097"
},
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