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

APPLICATIONS OF FUZZY MATHEMATICSIN STUDYINGHISTORICAL EARTHQUAKES AND PALEOSEISMICITYDe-yi FengSeismological Bureau of Tianjin, Tianjin, ChinaMing-zhou LinSeismological Bureau of Shanghai, Shanghai, ChinaKun- yuan ZhuangSeismological Bureau of Anhui Province, He fail ChinaABSTRACTSome concepts and methods of fuzzy mathematics, such as the membershipfunction, fuzzy multifactorial evaluation, principle of choosing theclosest degree of approaching, and others have been applied in the quantitativeevaluation of intensity of a historical earthquake and approximatedetermination of its source mechanism based on historical materials.A method of fuzzy description of macroscopic criteria for recognition ofpaleoseismic events is discussed briefly. For illustration of the suggestedmethods of fuzzy mathematics, the intensity and source mechanism ofthe 1920 Haiyuan (M = 8.5) great earthquake, the intensity of the 1937Hozhei (M = 7.0) earthquake, and some relics of ancient earthquakesappearing along the Xianshuihe fault zone are studied.1. IntroductionHistorical materials about earthquakes and paleoseismicity are very importantfor the studies of earthquake hazard assessment and earthquake engineering, becauseinstrumental seismic data are available only for the last 100 years. However.these materials often contain non-precise and very fuzzy information. Therefore, instudying historical earthquake and paleoseismicity, we must deal with treatmentsand analyses of fuzzy data, and some methods of fuzzy mathematics may be applicable.Since L. A. Zadeh advanced the fuzzy set theory in 1965, fuzzy mathematics hasdeveloped rapidly. At present, it attracts attention in various scientific and technicaldomains (see e.g., Dubois and Prade, 1980). In particular, fuzzy mathematics (fuzzysets theory) has been applied to various problems in earthquake research, includingearthquake engineering, earthquake hazard assessment, and earthquake prediction(Feng et al., 19836; Feng and Liu, 1985).This paper presents some preliminary results obtained in applying fuzzy mathematicsto the study of historical earthquake and paleoseismicity. Our emphasisis on developing some application methods of fuzzy mathematics. Obviously, oursuggestions are tentative and require further examination and evaluation.Historical Seismogramsand Earthquakes of the World311Copyright @ 1988 by Academic Press, Inc.All rights of reproduction in any form reserved.