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本文应用书布尔(Weibull)分布理论对发生在中国大陆板内的海城地震(1975)、龙陵地震(1976)、唐山地震(1976)和松潘地震(1976)的前兆时间和震中距的频度分布进行了定量分析。分别得到四个地震的前兆时空特征。结果为:海城地震的前兆时间分布中存在三种前兆,其时间的均值分别为418天、4.2天和2.8小时;唐山地震的前兆为两种,其时间的均值为497天和21天;龙陵地震和松潘地震的前兆似乎第三种前兆占优势,其时间的均值分別为50天和25天。前兆出现点的震中距的频度分布基本相似,但均值不同,其均值是:海城地震为139公里,龙陵地震为228公里,唐山地震为123公里,松潘地震为179公里。以上结果表明它们的时空特征是不相同的。其原因可能与中国大陆板内地震的类型有关。本质上与地震所处介质条件(均匀性、破碎程度等)有关。 分析结果表明,地震前兆并非在任何地点任何时刻杂乱无章的出现,而是在时间上具有阶段优势性,在空间上具有地区优势性。地震前兆的时间系列分析有助于认识地震的孕育过程和时间的预报,而地霞前兆的空间系列分析,则有助于前兆观测点的科学布局进而捕捉更多的前兆信息和地点的预报。
In this paper, Weibull distribution theory is applied to predict the frequency of precursory times and epicentral distances of Haicheng Earthquake (1975), Longling Earthquake (1976), Tangshan Earthquake (1976) and Songpan Earthquake (1976) Degree distribution was quantitatively analyzed. Four kinds of earthquakes are obtained respectively. The results are as follows: There are three precursors in the distribution of precursors of Haicheng earthquake, with mean time of 418 days, 4.2 days and 2.8 hours, respectively. The precursors of Tangshan earthquake are two kinds with the mean of 497 days and 21 days. The precursors to the Longling earthquake and the Songpan earthquake seem to be the predominant precursors of the third precursor, with averages of 50 days and 25 days respectively. The distributions of the epicenter distances of precursory spots were similar but with different mean values. The average values were 139 km for Haicheng Earthquake, 228 km for Longling Earthquake, 123 km for Tangshan Earthquake, and 179 km for Songpan Earthquake. The above results show that their spatio-temporal features are not the same. The reason may be related to the type of onshore earthquake in China. In essence, the conditions of the medium in which the earthquake is located (uniformity, degree of fragmentation, etc.). The results show that the earthquake precursors are not cluttered at any time and anywhere in the world, but have the stage predominance in time and the regional predominance in space. The time-series analysis of earthquake precursors can help to understand the process of geogenesis and the forecast of time, while the spatial series analysis of the earth-shap precursors helps the scientific layout of precursory observation points and thus capture more precursory information and the prediction of the places.