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震级和震中烈度的关系,人们通常采用李善邦研究中国近代地震时给出的公式M=0.58I_0+1.5,以及考虑了震源深度的影响后,付承义和刘正荣给出的公式M=0.68I_o+1.39Logh-1.40,这两个经验关系在中国地区一般是适合的。 可是我们在实践中不断发现,对于一次大地震之后的余震包括晚期余震,又有可以察觉到这个关系式有系统的差别。本文研究了近十年来中国华北地区的几次大地震后的余震资料,分别计算了考虑震源深度和不考虑震源深度两种情况下的余震震级和震中烈度的关系。通过最小二乘法计算给出 M=(0.69±0.09)I_o+(1.00±0.64),和采用二元线性回归求解得 M=(0.72±0.09)I_o+(1.03±0.93)Logh-(0.45±1.45)。 对比可见,显然余震有其本身的震级与震中烈度的关系式,和一般地震的这个关系不尽相同,即在震级相同的情况下,余震震中烈度偏低约半度。本文从余震发生的应力状态、介质特征以及余震活动的分布特点等方面,给予了初步的理论解释。
The relationship between magnitude and epicenter intensity is usually given by Li Shanbang’s formula M = 0.58I_0 + 1.5 when studying modern Chinese earthquakes and the formula M = 0.68I_o given by Fu Chengyi and Liu Zhengrong + 1.39Logh-1.40, these two empirical relationships are generally suitable in China. However, we find in practice that there is a systematic difference in the relationship between aftershocks after a major earthquake, including late aftershocks. This paper studies the aftershock data of several large earthquakes in the past ten years in North China, and calculates the relationship between the aftershock magnitude and the epicenter intensity under both the hypocentral depth and the hypocentral depth. M = (0.69 ± 0.09) I_o + (1.00 ± 0.64) was calculated by the least square method, and Logh- (0.45 ± 1.45) was calculated as M = (0.72 ± 0.09) I_o + (1.03 ± 0.93) using binary linear regression. In contrast, it is clear that aftershocks have their own relationship between magnitude and epicenter intensity, which is different from that of general earthquakes. In the case of the same magnitude, the intensity of the aftershocks is about halfway lower. This paper gives a preliminary theoretical explanation on the stress state, media characteristics and the distribution of aftershock activity after aftershocks.