  Simulations are used to determine the effect of inertia on athermal shear of
a two-dimensional binary Lennard-Jones glass. In the quasistatic limit, shear
occurs through a series of rapid avalanches. The distribution of avalanches is
analyzed using finite-size scaling with thousands to millions of particles.
Inertia takes the system to a new underdamped universality class rather than
driving the system away from criticality. Scaling exponents are determined for
the underdamped and overdamped limits and a critical damping that separates the
two regimes. Systems are in the overdamped universality class even when most
vibrational modes are underdamped.
