The most dangerous and destructive earthquakes that humanity has seen ussually are a combination of factors, from strong earthquakes to cities poorly built or not adecuate to endure the dangers that an earthquake might represent, a city built with the security necessary to endure a hard earthquake can survive a 7.5 earthquake in the richter scale, but till this day the strongest earthquake marked a 8.9 in the scale, everything above 8 would be extremely dangerous and destructive.
