Abstract: Whenchuan earthquake triggered many geo-hazards in Chenjiaba in Beichuan area, and Sunjiayuan rockslide was one of the biggest ones In the rockslide back-wall a special russet rock shell was revealed, which had strength higher than that of the underlying bed rock.A new definition named sliding-surface breccia was brought according to the characteristics and mineral identification of this special rock shell.By analyzing the mechanism of fast rock granular cementation, it is proved that under the severe earthquake and certain specific geological and topographical conditions, the temperature in the sliding zone can rise to meet the required temperature under which rock particles in the sliding zone can be conglomerated by ferruginous cementation.In addition, this temperature is far lower than the mineral melting temperature of rocks.