Historical Seismograms - Evidence from the AD 2000 Izu Islands ...

Historic a1 Mate rials of Chinese Earth q u a Ice s 165The great Tangslian Earthquake of 1976 attracted general attention to earthquakes.The Academy of Sciences, the Academy of Social Sciences and the StateSeismological Bureau of China deemed it necessary and also possible to revise theChronologiccd Tuble of Chanese Earthquakes. An editorial board was establishedin 1078. All provinces, metropolis and autonomous regions also organized theirrespective editorial groups. Hundreds of seismologists, historians, archaeologists,archivists, and librarians from various institutes and localities took part in thiswork.In the Ghronologicd Table, more than 1,GOO counties among the 2,000 and morecounties in our country have materials of historical earthquakes. Most of tlieni aredistributed in the eastern part of our country. For the bordering regions, historicalrecords are rare. For instance, in Xizang (Tibet) Autonomous Region (Figurel), only 30 earthquakes between 1893 and 1954 were recorded, of which 13 weredestructive. Recently, the Seismic Office and the Archives of Xizang AutonomousRegion looked up different sorts of historical docuirients which were never used before;such as, the archives of local authorities arid monasteries written in ancientTibetan, the Buddhistic classics, histories, biographies, the lunar calendar used bythe Zang (Tibetan) nationality, gazettes, iristruniental data and reports of expeditions,etc. Through careful selection, translation and verification, more than 800items, totalling about 600,000 Chinese characters, representing 437 earthquakesbetween 641 and 1980 were collected. For Taiwan Province, only 84 earthquakesbetween 1661 and 1951 were collected in the Chronological Table. In the new conipilation,the number of earthquakes collected increased more than ten times. Evenfor the densely populated eastern China, where culture and economy were well developed,we added many materials in the new edition. For example, nine destructiveearthquakes were supplemented for Jiarigsu Province in the Lower Yangtze Valley.Several of them occurred in the vicinity of Liyarig county (Figure I), where twodestructive earthquakes with magnitudes 5; to G occurred in 1974 and 1979, successively.In an investigation of the 1303 an> the 1695 earthquakes, both occurredin southern Shanxi Province, out of 2,386 stone tablets, 47 were inscribed withrecords of earthquakes. Besides, in northern Hainan Island, remains of villages andgraveyards can be seen at ebb tide, testifying the sinking of lowland near the coastduring the 1605 earthquake as recorded in historical documents.To check the materials concerning historical earthquakes is a difficult and painstakingwork. For example: the explosion of a powder niagazilie in Beijing in1626 was formerly misunderstood as a local destructive earthquake from historicalrecords. An item from local record was quoted as: “In Tang Dynasty (870 A.D.)Sicliuan was shaken strongly.” It was thus explained as “A big earthquake occurredin Sichuan”. But, tracing the original document, it wrote: “The city Chengdu inSichuan was encircled by the local minority natioiiality troops, arrows fall like rain,Sichuan was strongly shaken”. Really, it is the morale of the residents that wasshaken by the fear of the war and not the ground shaken by an earthquake. In theChronologzcal Table of Ghznese Earthquakes, there is an item saying: “In XichangCounty earth sliaked slightly”. The whole story as recorded in “History of MingDynasty” reads: “In Xicliang County, a fire ball like a wheel with a tail flew frointhe north and disappeared in the south, with a noise like thunder, the earth sliakedslightly.” It is clear that the shaking was caused by a comet.