Single station estimation of earthquake early warning parameters by using amplitude envelope curve

In this study, new empirical relationships to estimate key parameters in Earthquake Early Warning (EEW) system including magnitude, epicentral distance and Peak Ground Acceleration (PGA) are introduced based on features of the initial portion of Pwave’s amplitude envelope curve. For this purpose, 226 time series recorded by borehole accelerometers of Japanese KiKnet are processed for earthquakes with magnitudes from 3 to 7.2  and epicentral distances of less than 50 km. Hereby, an improved single station method for estimation of epicentral distance and two new methods for estimation of magnitude and amplitude of  are proposed based on exponentially envelope curve as  in known (B – Δ) method. A scaling relationship of B × Tr – Δ is proposed to estimate epicentral distance which is well correlated for larger earthquakes, with results more robust and reliable than the previous method (B – Δ). Nondimensional parameter,  depends on earthquake magnitude and  parameter in the abovementioned function. By using the features of acceleration envelope curve and peak amplitude of Pwaves, scale parameter  is proposed that is well correlated with magnitude and has capability of estimating magnitude with standard deviation of less than 0.77 magnitude unit.  is proportional to a part of area under envelope curve as a function of magnitude. Moreover, it is indicated that  in a single station can be estimated by using envelope curve characteristics of initial Pwaves portion.