3D-1D broadband simulations of ground motion are normally performed by using a hybrid approach where full wave numerical methods are used for the low frequencies and a stochastic contribution has added a posteriori to achieve high frequencies. The cross-over for hybridization is established empirically in a band between about 0.5 Hz and 2 Hz depending on the earthquake magnitude size, distance, local structure and shape of Fourier spectra of low frequency synthetic seismograms.
Caro Alessandro,
to my knowledge there are no papers that specifically focus on the cross-over frequency between a deterministic and a stochastic modeling. In our paper on hybrid modeling of L'Aquila earthquake ground motions published on JGR (that you can find on my page):
"Complexity of theMw6.3 2009 L’Aquila (central Italy) earthquake: 2. Broadband strong motion modeling"
we discussed about this issue in Section 7. You can find some relevant references there.
I hope you find this of some help.
Ciao
Gabriele
Dear Gabriele,
thanks a lot. I was aware of your good work on modeling the L'Aquila eqk rupture. I would like to share some doubts about using hybrid techniques in upper bound ground motion estimates. Hybrid techniques (when EGF are not available) needed to be anchored indirectly to ground motion prediction equations in the high frequency range. However, for long return periods, very low probabilities (e.g. nuclear power plants) and unlikely earthquakes, GMPE cannot provide an adequate support to shape the spectral behavior at high frequency. This makes the estimate of the upper bound of ground motion largely uncertain and the DSHA useless for design. Do you agree about ? Moreover earthquake sources are generally known at low frequencies < 1 Hz and often the same input source parameters are used even in the computation of the high frequency content.
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