around the compact star[@woo88]. If the formation of such a reverse shock is possible, Chevalier and other authors[@che89] investigated the possibility of the accretion with hypercritical (or “super Eddington”) accretion rate, and found that the total accreted matter could be as high as $10^{-3} M_\odot$ for a normal type II supernova, which is much higher than the maximum crust mass a strange star can sustain. In such cases, the strange star formed from the explosion should have a thick crust with maximum mass. However, the Chevalier’s scenario does not include the influences of rotation and magnetic fields. When these effects are taken into account, more likely, the backfalling materials will form a disk[@mich88] rather than just directly falling back onto the surface of the compact star. According to Michel[@mich91], such a disk is essential for pulsar magnetospheric electrodynamics. Some models also invoked such a disk to interpret the emission behavior of the anomalous X-ray pulsars[@chn99]. Thus it is very likely that the mass which falls back to the pulsar surface should be tiny compared to the maximum, as Usov[@usov97; @usov98] suggested.

Let us present a rough estimate of the mass and the thickness of the crust formed due to the 