The water is most likely seeping in a crack between the poured floor and the basement wall. I assume that the basement floor is below grade at this point. That being the case, what you have when you have a hard rain or rain over a period of days and raises the water table to the point that it finds it's way into your basement. It is also possible that you do not have proper drainage on that side of the house and water does not flow away but toward the house.