abstract (from Grecksch, G & Kümpel, H.-J. (1997). Geophys. J. Int., 129, 113-123)

Statistical analysis of strong-motion-accelerograms and its application to earthquake early warning systems

In view of increasing damage due to earthquakes and the current problems of earthquake prediction, real-time warning of strong ground motion is attracting more interest. In principle, it allows short-term warning of earthquakes while they are occurring. With warning times up to tens of seconds it is possible to send alerts to potential areas of strong shaking before the arrival of the seismic waves and to mitigate the damage, but only if the seismic source parameters are determined rapidly. The major problem of an early warning system is the real-time estimation of the earthquake's size.

We investigated digitized strong-motion accelerograms from 244 earthquakes in North- and Central America between 1940 and 1986 to find out, whether their initial portions reflect the size of the ongoing earthquake. Applying conventional methods of time series analyses we calculated appropriate signal parameters and describe their uncertainties in relation to the magnitude and epicentral distance. The study reveals that the magnitude of an earthquake can be predicted from the first second of a single accelerogram within ±1.36 magnitude units. The uncertainty can be reduced to about ±0.5 magnitude units if a larger number (>8) of accelerograms is available, which requires a dense network of seismic stations in areas of high seismic risk.