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1957年公布的中国地震烈度区划图其编图原则有两个,一个是过去历史上发生过多大的地震,将来还会重演,另一个是地质条件相似的地方地震强度相似。本文对这两个原则进行了修正。对第一个原则的修正主要是用统计法、位错法和热传导法求出大震重复周期,在大震间歇期间,烈度可以降低一两度。对于第二个原则的修正主要是考虑到我国大陆内主应力的分布是大体一致的,错动旋性也是一致的。在此情况下,当一个断层上发生大震后,相距不太远的平行断层就会减震,而不是地质条件相似必然要发生类似的大震。对于相交汇的两个断层来说,一个相当于垂线,可称垂断层,另一个相当于底线,可称底断层。如果底断层发生了大震,则垂断层上就减震了,简称“底震垂减”;如果垂断层上发生了大震,则底断层上可能还会相继发生大震,可称“垂震底继”。根据减震作用的观点可以在全国寻找一些安全区,以利于经济建设。如果一个断层不是发生大震,而是在很长的地段内发生蠕滑,则相邻的平行断层也可减震。由减震作用可以解释地震活动的整带跨距迁移,也可解释相平行的断层上的地震分布的平行四边形格局。为了探明已发大震的断层是否已锁住,可用被外因调制的小震活动性来抽查。对于平行断层来说,异旋是加震的。本文得到的主要结果如下: 1.大震重复时间本文收集了中国活动断层滑动速率的数据,得到了最大滑动速率为25mm/年,平均滑动速率为10mm/年,以及最小滑动速率为0.1mm/年。据根我们在1973年得到的震级与错动幅度的经验关系式Dcm=10~(0.52Ms-1.25) 则强震的重复时间可分别表示为: T_1=Dcm/V_(最大) T_2=Dcm/V_(平均) T_3=Dcm/V_(最小) 式中V为滑动速率。由上述数据可求得在不同滑动速率下的大震重复时间,如表1所示。在不同的建设地区,可根据其建设项目的重要性以及当地活动断裂的大致滑动速率来选择表1中的大震重复时间。2.强震造成的减震距离对于一个走滑震源断层,在其垂直方向上位移衰减至1米的距离R为R=H/1.17cot(π/2 100cm/Dcm) 上式H为断层面深度,我们取20公里,则上式可写为R=20/1.17(cot(π/2 100/D)) 对于不同震级地震的减震距离可表示于表2 关于由热传导计算大地震重复时间问题留待以后专文讨论。
The zoning map of China’s seismic intensity released in 1957 has two principles of how it is compiled. One is the earthquakes that have occurred in the past in history and will be repeated in the future. The other is similar earthquakes of similar geological conditions. This article has amended these two principles. The first principle is mainly revised by statistical method, dislocation method and heat conduction method to find the repetitive cycle of large earthquakes during the intermittent period, the intensity can be reduced by one or two degrees. The amendment to the second principle is mainly based on the fact that the distribution of the principal stresses in China is generally consistent and that the wrongly-turning motions are also consistent. In this case, when a large earthquake occurs on one fault, the parallel faults that are not far apart will be damped instead of the similar earthquakes which are similar in geological conditions. For the intersection of the two faults, an equivalent to the vertical line, can be called vertical fault, the other is equivalent to the bottom line, can be called the bottom fault. If a major earthquake occurs in the bottom fault, then the earthquake will fall on the vertical fault, which is referred to as “vertical drop”; if a large earthquake occurs in the vertical fault, then a large earthquake may occur on the bottom fault, End of the sequel. " According to the role of shock absorption in the country can look for some safe areas in order to facilitate economic construction. If a fault is not a major earthquake occurs, but in a very long section of creep occurs, the adjacent parallel faults can also be shock-absorbing. The damping effect can explain the whole-span migration of seismic activity and also explain the parallelogram pattern of the seismic distribution on the parallel faults. In order to ascertain whether a fault has been locked in a major earthquake, we can use the activity of small earthquakes modulated by an external factor to check. For parallel faults, heterodyne is additive. The main results obtained in this paper are as follows: 1. Large earthquake repetition time This paper collects the data of the active fault slip rate in China. The maximum slip rate is 25mm / year, the average slip rate is 10mm / year and the minimum slip rate is 0.1mm / year. According to the empirical equation Dcm = 10 ~ (0.52Ms-1.25), the magnitude of the magnitude and the magnitude of the misalignment obtained in 1973 can be respectively expressed as T_1 = Dcm / V_ (maximum) T_2 = Dcm / V_ (average) T_3 = Dcm / V_ (minimum) where V is the slip rate. The above data can be obtained at different sliding rates of large earthquake repetition time, as shown in Table 1. In different areas of construction, the large earthquake repetition time in Table 1 can be chosen according to the importance of its construction project and the approximate sliding rate of local active faults. 2. Damping Distance Due to Strong Earthquake For a strike-slip focal source fault, the distance R in the vertical direction of which it decays to 1 m is R = H / 1.17cot (π / 2 100cm / Dcm) where H is the fault plane Depth, we take 20 km, then the above equation can be written as R = 20 / 1.17 (cot (π / 2 100 / D)) For different magnitudes of the earthquake damping distance can be expressed in Table 2 on the heat transfer calculation of large earthquake repetition time Problems to be discussed later.