Zhangjiakou", "in a few years") to warrant large-scale societal and economic disruption. Such disruptions could be serious: a false alarm in October, 1976, issued by the Shaanxi provincial government, is estimated to have disrupted the lives of 65% of the population of that province for half a year. It has also been estimated that "in the fall of 1976 about 400 million of the then total population of 930 million of China spent some nights in temporary earthquake shelters." This illustrates the classic dilemma of earthquake prediction: increasing the sensitivity to the possibility of an earthquake (i.e., reducing the failure to predict) increases the number false alarms, which often has a significant cost. Comparison Comparison of the Tangshan death toll – officially 242,419—with other earthquake disasters is problematical because of uncertainty in the statistics. For example, the 1556 Shaanxi earthquake (estimated magnitude of ~8) is generally said to have been the deadliest earthquake disaster in history, with 830,000 deaths, based on Chinese historical records. However, a Chinese language source argues for only 530,000 deaths from the earthquake itself, with the larger number being the total reduction of population due to deaths from all causes (including exposure, disease, and famine) as well as people leaving the region due to economic collapse. Another Chinese source states (without citing any sources) that the 1556 earthquake killed only about 100,000 directly, with another 700,000 dying of disease. Depending on what basis is used, the Tangshan disaster can thus be considered as approximately one-third, one-half, or twice as deadly as the Shaanxi disaster. The other five deadliest earthquake disasters known in history, with magnitudes ranging from 7.0 to 9.1, have had death tolls just under that of Tangshan's: 1138 Aleppo earthquake (Syria) magnitude unknown, ~230,000 deaths. 2004 Sumatra earthquake (Indonesia) M 9.1, 227,898 deaths, mostly due to tsunamis. 2010 Haiti earthquake M 7.0, 100,000–316,000 deaths. 1920 Haiyuan (Gansu) earthquake (China) M 7.8, 200,000–273,400 deaths. 856 Damghan earthquake (Iran) magnitude unknown, ~200,000 deaths. Other notably deadly earthquakes in the past century include: 1923 Great Kantō earthquake (Japan) M 7.9, 142,800 deaths, mostly due to fire. 1948 Ashgabat earthquake (Turkmenistan) M 7.3, 110,000 deaths. Although unprepared, compared to other earthquake disasters Tangshan did not experience significant common secondary disasters arising from fire, tsunami, landsliding, or flooding due to blocking of rivers or breaching of dikes. A dam holding back a large reservoir just above Tangshan was seriously