On correlation of seismoscope response with earthquake magnitude and Modified Mercalli Intensity

A quantitative measure of the Modified Mercalli Intensity Scale for earthquakes in the western United States has been developed by correlating the peak seismoscope relative displacement response, S_d, with the reported site intensity, I_(MM). This correlation can be approximated by S̄_d(cm) ≈ 1/49.2(10^(0.288 I_MM)) for I_(MM) ≦ VIII and is characterized by one standard deviation of about 0.7 S̄_d. The data used in this study do not indicate an obvious type of dependence of S_d on local site conditions. A method for computing the analog of the local earthquake magnitude, M_(seismoscope), has been presented for possible use in strong-motion seismology and for scaling earthquakes by close-in measurements, when other seismological instruments may go off scale.