  We present the results of numerical simulations of an atomistic system
undergoing plastic shear flow in the athermal, quasistatic limit. The system is
shown to undergo cascades of local rearrangements, associated with quadrupolar
energy fluctuations, which induce system-spanning events organized into lines
of slip oriented along the Bravais axes of the simulation cell. A finite size
scaling analysis reveals subextensive scaling of the energy drops and
participation numbers, linear in the length of the simulation cell, in good
agreement with the observed real-space structure of the plastic events.
