  Two Mpc-size contact discontinuities have recently been identified in the
XMM-Newton and Suzaku X-ray observations of the outskirts of the Perseus
cluster (Walker et al. 2020). These structures have been tentatively
interpreted as "sloshing cold fronts", which are customarily associated with
differential motions of the cluster gas, perturbed by a merger. In this study
we consider an alternative scenario, namely, that the most prominent
discontinuity near the cluster virial radius is the result of the collision
between the accretion shock and the "runaway" merger shock. We also discuss the
possible origin of the second discontinuity at ~1.2 Mpc.
