Index Geophysics

eng Stresses and intermediate frequencies of strong earthquake acceleration

hrv Napetosti i središnji interval frekvencija pri akceleraciji tla za jakih potresa

eng The peak of smooth Fourier amplitude spectra, ((FS(T))max, of strong motion acceleration recorded in California is modelled via dimensional analysis. In this model, the spectrum amplitudes are proportional to (1) sigma - the root-mean-square (r.m.s.) amplitude of the peak stresses on the fault surface in the areas of high stress concentration (asperities), and (2) (log10N)1/2, where N is the number of contributing (sampled) asperities. The results imply simple, one asperity, earthquake events for M ≤ 5, and multiple asperity events for M ≥ 5 (N ~ 10 near M = 7and N ~ 100 near M ~ 8). The r.m.s. value of the peak stress drop on the fault, sigma, appears to increase with magnitude for M ≤ 6, and then it levels off near 100 bars, for M ≥ 6. For M > 6, ((FS(T))max continues to grow with magnitude, because of the larger number of asperities from which the sample is taken (N ~ 100 for M = 8), not because of increasing sigma.

hrv Ekstremi izgla|enih Fourierovih spektara, (FS(T))max, akcelerograma jakih potresa u Kaliforniji modelirani su dimenzionalnom analizom. U tom modelu spektri amplitude proporcionalni su sa: (1) sigma– r.m.s. iznosu amplitude vršnih napetosti u područjima visoke napetosti na rasjednoj plohi i (2) (log10N)1/2 – gdje je N broj takvih područja. Jednostavni modeli rasjeda s jednim područjem visoke koncentracije napetosti prikladni su za opis potresa s magnitudom M ≥ 5, dok za veće magnitude u obzir treba uzeti više takvih područja (N ~ 10 oko M = 7 i N ~ 100 za M ~ 8). r.m.s. iznos parametra sigma čini se da raste s magnitudom za M ≥ 6, dok je za veće magnitude približno konstantan i iznosi oko 100 bara. Za M > 6, (FS(T))max raste s magnitudom zbog
velikog broja područja visoke napetosti koja doprinose spektru (N ~ 100 za M = 8), a ne zbog povećanja sigma.

Trifunac, M. D.

eng Strong earthquake acceleration; earthquake stress

hrv velika akceleracija potresa; vršne napetosti

Andrija Mohorovicic Geophysical Institute

1997

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Geofizika

ISSN 0352-3659 (Print)

ISSN 1846-6346 (Online)

Volume 14

Issue 1

eng

info:eu-repo/semantics/openAccess

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