Frequency domain estimation method of the characteristic period of the P wave of earthquakes

Elena Serea ^* Codrin Donciu Marinel Costel Temneanu

• Gheorghe Asachi Technical University of Iași, Iași, Romania

The earthquake alert of the early warning systems exploits the time delay that the surface waves have in reference to the P waves and estimates the magnitude based on the interpretation of the specific parameters of the P waves. One of the most commonly used parameters for estimating the moment magnitude of an earthquake is the characteristic period measured in the first 3 s from the appearance of the P wave. The classic method determines the characteristic period in the time domain, by using based on the velocity and displacement wave's acquired samples. In this paper, we present a new method for estimating the characteristic period through its corresponding frequency of the characteristic period. This method includes zero padding of the P-wave sequence, conversion of the extended sequence from the time domain to the frequency domain, identification of local frequency maxima, and calculation of the weighted average of the frequency based on the identified maxima. Tests conducted on synthetic signals, as well as standard deviation evaluation tests for simultaneous recordings at several seismic stations, revealed better performance than the reported ones in terms of noise immunity and number of false alarms.. travel speed, they will reach their destination first and can be a source of information regarding the destructive waves that will reach their destination later. Moreover, P-wave based EEWSs can work in tandem with Seismicity indicator-based systems as those making use of the Gutenberg-Richter law, to increase the probability of detection of major earthquakes [1, 2, 3].