Why seismologists usually cannot tell when shocks mil strike
On a bitterly cold day in February 1975, the Communist Party chiefs in Haicheng, a city in northeastern China, convened in emergency session. They had just learned from seismologists that various signs, including changes in the water level of wells, pointed to an imminent earthquake. Convinced the threat was real, they issued an order to evacuate all homes and hospitals, close down shops and factories and turn off gas mains and furnaces.
That night, while thousands huddled in open fields or watched special film showings...