Why do some big earthquakes cause very little damage, while other relatively small earthquakes are very destructive?
The two principal factors affecting damage are: degree of isolation (how far is the epicenter from major cities?), and type of construction (are the buildings easily damaged?). For example, on 23 May 1989 a quake with magnitude Mw of 8.1 occurred near Macquarie Island, about 500 km south of New Zealand. Since the nearest city was about 500 km distant, it caused no damage whatsoever. In contrast, relatively small but deadly earthquakes occur in regions of dense population where buildings are of unreinforced adobe, stone, or concrete; these structures fail easily and crush inhabitants. An example is the Managua, Nicaragua earthquake of 23 December 1972; it had a magnitude MS of only 6.2 but it killed about 6,000 people. An old seismology saying is, “Earthquakes don’t kill people, buildings kill people.” A large earthquake in the tropics might shake down every grass hut within 500 km. But, afterwards the people simply rethatch their homes and go on with their lives. Q: How commonly do “gr
