Earthquake Magnitude Estimate for Earthquake Early Warning (EEW) System: an Automization from P-Wave Time Window Analysis

A real time disaster prevention countermeasure against earthquake strong motion is Earthquake Early Warning (EEW) System. The main framework for EEW implementation is to estimate the earthquake size by different observed parameters measured on the signal onsets. Size of an earthquake depends on the initial rupture process that takes place at the source. In this study Brune's model contributed for the physical process of earthquake generation has been used to fit in the acceleration and displacement source spectra of the strong motion record in a selected window length to estimate the size ofan earthquake in real time. The spectral parameters: 90 (displacement amplitude at low frequency), f; (comer frequency) and fjm (high cut-off frequency)_ estimated from the fitted model have been used to compute the seismic moment. Some 1726 strong motion records of 106 earthquakes with magnitudes ranging from 5 to 7.2 and epicentral distance less than and equal to 60 km in different parts of Japan have been analyzed. An attempt is made to empirically estimate the minimum time required to quantify the magnitude. The analytic result shows that a time window of 5 sec provides a good estimate of the magnitude with a standard deviation of 0.3 making it feasible to be used in EEW.