Are stress drop and rupture velocity of earthquakes independent? Insight from observed ground motion variability

We demonstrate that the variability of the peak ground acceleration (PGA) generated by earthquakes can be simply related to the variability of stress drop (Δ τ ), rupture velocity ( V r ) and their correlation. By compiling recent observations of variability of Δ τ and V r , we show that the hypothesis of independence between Δ τ and V r leads to an overestimation of the PGA variability. We suggest that Δ τ and V r must be anticorrelated so as to match recent observations of PGA variability.