There are three problems, besides the concealment.
First, you only 怀疑是原来Saler为了故意隐瞒问题才这么做的, where is the evidence? Your doubt cannot be shown as evidence. Even if the owner did conceal, it still depends on other things. For example, how long did it take to close? What is the exact clause of risk of loss in your sales contract? Without any express clause, most courts apply doctrine of equitable conversion during the closing period so that you will take the risk of loss. Means, if the crack happened during this period it is your responsibility, not the owner, even if he still occupies the house.
Second, you said 很多房子的basement的墙上都有裂缝. Which means, this kind of crack is normal so that it will not make a title unmarketable, at least not to a reasonably prudent person. Do you think with cracks those other houses you looked at would not sell? You may ask the opinions of a realtor to find if it is.
Third, you said 这种裂缝不会马上使房子有什么问题. The law will only handle real cases and controversies that you are suffering imminent injury or at least imminent threat of injury. It sounds like the problem right now is minimal and it will injure you, probably, sometime in the future. Until then, you have no case.