Random Processes for Earthquake Simulation

Criteria presented for the evaluation of earthquake simulation processes relate to the autocovariance function, maximum acceleration response spectra, and nonstationarity of the process. Two previously used and two new processes are examined with respect to these criteria by means of theoretical and simulated results. The previous processes develop a nonstationary white noise for input to a linear filter and take the filter output as the simulated ground acceleration. They are identical except for filter properties. Neither of these processes complies with all the criteria. One fails to provide reasonable response spectra; the other produces an unrealistic ground-velocity variance function that does not disappear with time. The new processes incorporate weighting functions that produce correlated, nonwhite filter inputs. One of these produces response spectra with undesirable irregularities. The other, which employs an exponential decay-type weighting function, complies with all criteria and is recommended as a suitable model for earthquake simulation. Additional relationships are examined for rms and maximum oscillator response spectra.