Tsunamis are sequence of huge waves caused by underwater earthquakes or volcanic eruption leading to large amount of deaths. The earthquake causes movement of the seafloor and the massive displacement of large amount of water which in turn leads to a Tsunami.
The earthquakes are as a result of the tectonic plates sliding each other causing faults and cracks on the earth crusts.
Because now they are not forcing the rule to kill female children any more so now the females grow up and they have their children. the children are not judged by their gender.