Hello,
I need a small clarification on artificial and synthetic accelerograms. To my knowledge, synthetic accelerograms are those which can be derived from seismological parameters and artificial accelerograms those which can be derived from spectrum compatible. If my explanation is wrong, kindly correct me.
Another clarification on synthetic accelerogram is, why do we multiply source, path and site terms in generating synthetic accelerogram. To my knowledge, source is related to magnitude, path is related to hypocentral distance and site is related to local geology. If my explanation is wrong, kindly provide detailed information.
I'd like to say something to the second point : Wny do we multply....Source and wave propagation effects can be nicely separated in the frequency domain as long as we consider a point source. The treatment of extended sources is a bit more complicated - it needs to consider the source to be composed of small subsources, and for each of them the wave.propagation effects is accounted. This is done in programs like EXSIM (see, e.g., Boore, 2009, Bull.. Seism Soc. Soc Amer). The separation of site an path follows an "engineering philosophy" but is rather questionable, in particular if site effects ara caused by the presence of specific gelogoical features such as low velocity layers at the surface. Then site and path effects are not independent on each other : A low velocity layer overlying solid rock causes strong amplificition. If the subsurface material has lower impedance then amplification is much less. The latter situation is met, for instance, in sedimentary basins.
for the second part. the synthetic accelerogram represents the ground motion which is the convolution of the source, the path, the site effect and the instrument response. but we do this convolution in frequency domain as multiplication.
Source, propagation path and site effect are combined whiel developing a synthetic ground motion at a site because the ground motion at a site is a collective effect of all these three factors. First the motion is generated at the source (sorure characteristics), then it travels from the focus through crustal medium to bedrock below the site of interest (propagation path) and this ground motion from the bedrock once transfer from bedrock to the surface where the building is constructed, it undergoes change in its amplitude, frequency content because of local site effect.
I hope this clarifies your doubt about synthetic ground motions.
To my knowledge synthetic accelerograms are based from scratch (wfrom white noise) which is treated to match a given spectra. Artificial are modified from original events.
This article has a Matlab code included which can be used to generate artificial accelerograms and has instructions on how to use the code:
https://onlinelibrary.wiley.com/doi/full/10.1002/eng2.12129
If you need any help please feel free to contact
Best
Fernando
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