Earthquakes

The effects of earthquakes are well known. Less known are their causes, hidden in the shifting pressures of the substrata of the earth. Their an nual number has been estimated at from 50,000 to 1,000,000; accurate instru mental locations date from about 1918. At present, seismographic stations register 600 to 700 a year, over a hundred of which are of major intensity. They cluster in two zones, one bordering on the Pacific Ocean and representing 80 per cent of the total energy released, the other running from Burma through the Himalayas westward through Europe's Alps. However, earthquakes may occur anywhere. They seem to run in cycles, but accurate prediction is impos sible. Planning can do much to reduce damage, but their relative rarity and unpredictability make planning difficult; it encounters barriers in inertia, self- interest, and long-term costs.—Ed

Geography · Physical geography · Seismology · Earthquake Detection and Analysis · Geology · Seismology and Earthquake Studies