SAN JUAN, Puerto Rico (AP) — Puerto Rico’s government is opening public schools next week without knowing if they can withstand a big earthquake as concerns grow about weakened infrastructure that is displacing thousands of students. By Friday, engineers had inspected 561 out of the islandís 856 public schools and found that 9% are unsafe as a result of damage caused by a recent 6.4 magnitude quake and strong aftershocks. The ongoing inspections, however, are not to determine whether the schools can survive another strong earthquake or if they were built using short columns, considered a risk factor, said engineer Carlos Pesquera, whom the governor recently named as a risk mitigation adviser.