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71.
72.
Commonly used earthquake “whole process” frequency - magnitude and strain energy - magnitude laws are merged to obtain an
analytic expression for an upper bound magnitude to regional earthquake occurrenceM
3, which is expressed primarily in terms of the annual maximum magnitudeM
1 and the magnitude equivalent of the annual average total strain energy releaseM
2. Values ofM
3 are also estimated graphically from cumulative strain energy release diagrams. Both methods are illustrated by application
to the high seismicity of the circum-Pacific belt, using Duda’s (1965) data and regionalisation. Values ofM
3 obtained analytically, with their uncertainties, are in agreement with those obtained graphically. Empirical relations are
then obtained betweenM
1,M
2, andM
3, which could be of general assistance in regional seismic risk considerations if they are found to be of a universal nature.
For instance.M
3 andM
2 differ by one magnitude unit in subregions of the circum-Pacific. 相似文献
73.
Two moderate earthquakes of magnitudesM
s=5.5 and 6.0 occurred in 1974 and 1979, respectively, in the Liyang region, Jiangsu Province, China. The distance between the two epicenters is less than 20 km and their source mechanisms are very similar. In comparing these two earthquakes, we notice that the similarity of coseismic effects is consistent with a scaling law. The isoseismals of the two earthquakes resemble each other in overall shape but the difference of intensity between pairs of coincident isoseismals is one degree. The precursory seismicity patterns of the two events, such as seismic gaps and preshock swarms, are similar, but do not scale to magnitudes of mainshock. The latter phenomenon may reflect the regional tectonic structure, assuming the entire region to be subjected to the same stress. 相似文献
74.
Dynamic faulting under rate-dependent friction 总被引:2,自引:0,他引:2
We discuss the effects of rate-dependent friction on the propagation of seismic rupture on active faults. Several physicists using Burridge and Knopoff's box and spring model of faulting have proposed that fault complexity may arise from the spontaneous development of a self-similar stress distribution on the fault plane. If this model proves to be correct, it has important consequences for the origin of the complexity of seismic sources. In order to test these ideas on a more realistic earthquake model, we developed a new boundary integral equation method for studying rupture propagation along an antiplane fault in the presence of nonlinear rate-dependent friction. We study rupture dynamics of models with single and twin asperities. In our models, asperities are places on the fault with a higher value of prestress. Othewise all fault parameters are homogeneous. We show that for models with such asperities, a slip velocity weakening friction leads to the propagation of supersonic healing phases and to the spontaneous arrest of fracture if the prestress outside the asperities is low enough. For models with asperities, we can also observe narrow slip velocity pulses, qualitatively similar to the so-called Heaton pulses observed in some earthquake accelerograms. We also observe a complex distribution of stress after the rupture that depends on details of the initial distribution of asperities and on the details of the friction law. 相似文献
75.
本文用数盒子法计算了1979年3月2日固镇5.0级、1974年4月22日溧阳5.5级和1979年7月9日溧阳6.0级地震前后小震空间分布分形集合的奇异性谱f(α),详细讨论了f(α)谱所揭示的主震前后各阶段小震空间分布从稀疏到密集的各种密度分布不均匀性的定量特征。经分析可以看出,奇异性谱f(α)较多重分形谱Dq的概念更直观、清晰,它包含了空间分布的全部信息,且计算量明显减少。 相似文献
76.
根据地形、地貌、地震地质特征以及地震活动情况研究了准噶尔西界山带的地震活动性。认为1990年6月14日原苏联斋桑7.3级地震和同年8月3日6.8级地震应属准噶尔西界山带地震。显然,准噶尔西界山带范围内的地震烈度区划(1990)应该调整。 相似文献
77.
78.
79.
80.
研究了1970年以来发生于祁连—海原地震带的18次中强地震序列特征,在此基础上确定了地震序列类型,研究了各种类型地震序列的分布规律.结果表明,该带的18次中强地震序列中有44%为主震型,56%为孤立型.西海固地区的中强地震序列一般为孤立型;101°~103.5°E范围内的祁连山中东段的中强地震序列一般为主震型;99°~101°E范围内的祁连山中段为孤立型和主震型序列并存;99°E以西的祁连山西段的中强地震序列为孤立型.将上述结果应用于2000年6月6日景泰MS5.9地震的震后趋势快速判定,判定结果与实际地震活动情况符合. 相似文献