Empirical Relationships based on the P-wave Envelop for Distance and Magnitude Estimation for Earthquake Early Warning in Iran

The main goal of an Earthquake Early Warning (EEW) system is to reduce the damaging effects of the hazardous earthquakes. The characterization of an earthquake for EEW includes most importantly, the estimates of its size (magnitude) and location. In this study, the distance and magnitude of the selected earthquakes were estimated using the envelope of the initial part of the P-waveforms deploying a single seismic record. The method so called "B-delta" [۱] is used to find the EEW parameters. In total, ۱۲۱۰ records (vertical component) with ۴.۰ £M ۷.۷ and epicentral distance up to ۳۰۰ km is used. The root mean square error (RMSE) of epicentral distance estimations using ۲ and ۳ sec P-wave time windows are ۰.۲۶۰ and ۰.۲۶۱ on a logarithmic scale respectively. Additionally, the C-D method [۲] was performed to check if this method provides more accurate estimates. Results show no significant differences between the final estimates of the two methods. Furthermore, using the obtained epicentral distance, the magnitude was estimated by employing empirical magnitude-amplitude relationships. The magnitude RMSE of both methods is in range of ۰.۶-۰.۷. Results suggest that the final magnitude of the large events would be underestimated using just few seconds of P-wave; however, the magnitude estimates can be used as the minimum threshold for the final size of the ongoing event. Moreover, short term average/long term average method was used for automatic P-wave arrival detection. The result shows ۷۶% success in P-wave arrival detection. This method can be utilized in real time EEW practices.

Keywords:

Earthquake Early Warning System , P-wave , B-delta method , Single Station method , Strong Motion Data , Iran