Ground motion attenuation model for peak horizontal acceleration from shallow crustal earthquakes

Spatial distribution of ground motion data of recent earthquakes unveiled some features of peak ground acceleration (PGA) attenuation with respect to closest distance to the fault (R) that current predictive models may not effectively capture. As such, PGA: (1) remains constant in the near-fault area, (2) may show an increase in amplitudes at a certain distance of about 3-10 km from the fault rupture, (3) attenuates with slope of R-1 and faster at farther distances, and (4) intensifies at certain distances due to basin effect (if basin is present). A new ground motion attenuation model is developed using a comprehensive set of ground motion data compiled from shallow crustal earthquakes. A novel feature of the predictive model is its new functional form structured on the transfer function of a single-degree-of-freedom oscillator whereby frequency square term is replaced with closest distance to the fault. We are proposing to fit ground motion amplitudes to a shape of a response function of a series (cascade) of filters, stacked separately one after another, instead of fitting an attenuation curve to a prescribed empirical expression. In this mathematical model each filter represents a separate physical effect.