A Physical ground for the scaling of Peak Ground Acceleration (PGA) with the integral of squared velocity ( I2 Vp and its potential for Earthquake Early Warning

Abstract

Abstract One of the main goals of an Earthquake Early Warning System (EEWS) is to estimate the expected peak ground motion of the destructive S-waves using the first few seconds of P-waves, thus becoming an operational tool for real-time seismic risk management in a short timescale. EEWSs are based on the use of scaling relations between parameters measured on the initial portion of the seismic signal, after the arrival of the P-wave. Scope of the present work is to study the physical basis of the scaling laws observed between the peak ground acceleration (PGA) and the integral of the squared velocity ( I2 vp ). Based on Brune’s model, which is one of the most widely adopted earthquake source models, we explore the physical principles of the scaling relations between the root mean square (rms) of the velocity acceleration recorded in the first few seconds after P-wave arrival and acceleration (recorded in S-waves) and the II2 vp . Assuming a relation between the PGA and the rms values estimated, the scaling of PGA with the integral of the squared velocity (I2 vp ) which is calculated directly from the first few seconds-long signal window (T) after the P-wave arrival obtained. The latter formulation opens the possibility of using such laws for on-site and inter-site earthquake early warning.