Canie-I may be wrong, but I think that the contacts between sand grains in a sandstone are weaker than after they are broken-the sides of the fault fit together better or have a larger contact area after they are broken. So, cementing may not be required, although it probably happens and is part of the process. One question would be whether these deformation bands only form in the upper couple of km of crust, and not down where most western earthquakes occur. Since sandstone is only going to be in sedimentary basins, it could not occur deeper than the basin....but there Ventura basin in California has something like 8 km of sediment younger than 5 million years...but, does sandstone alter too much at, say, depth of 10 or 15 km below Ventura basin to behave this way? Chris