Shallow Slip Deficit: An Intrinsic Property of Continental Earthquakes, Slightly Enhanced by Fault Maturity

Abstract A depletion of earthquake slip in the shallow crust (shallow coseismic slip deficit, or coseismic SSD) has been observed on <30, Mw ≥ 6 continental earthquakes, and attributed to the immaturity of the ruptured faults. We question the factors that contribute to the coseismic SSD. We built the largest earthquake source model database available to date, with 1078 models providing coseismic SSD estimates on 163 Mw ≥ 6, various slip mode, continental earthquakes worldwide since 1990. We also built a database providing their fault maturity parameters (initiation age, net displacement, length, slip rate). Our combined earthquake‐fault analysis reveals that coseismic SSD of continental earthquakes, whatever their slip mode, is primarily controlled by the relation between their magnitude and peak slip depth, and, to a much lesser extent, by the fault maturity. A model where earthquake slip produces zero stress drop on the shallow velocity strengthening fault section reproduces the data well.