If Velvets are throwing it at you as part of a blockstring, you can hard counter it by jumping out of the blockstring. There's no true blockstring into Eruption, and A Eruption gets rocked by jump-ins.
Otherwise, block low. Generally speaking, if you're out of C Shatter range, you can just hold down back and not get outright hit by anything Velvet has for you, though you'll need to get in somehow to damage her.