Abstract: According to the “Netlike Plastic-Flow” continental dynamics, the transition of deformation regime from brittle in shallow layer to ductile in deep layer in the lithosphere and the controlling effect of netlike plastic-flow result in the intraplate multi-layer tectonic deformation. What have been measured using the GPS method or fault-slip-inversion method can deal only with the surface and shallow crust. The strain rates in the seismogenic layer can be estimated using the “earthquake-recurrence-interval method”, in which the strain rate is calculated in terms of the recurrence interval of two adjacent earthquakes occurring one after another and the seismic probability of the posterior one, and the strains of the plastic-flow network in the lower lithosphere using the “conjugate-angle method” on the basis of the relationship between the conjugate angles and the compressive deformation of the network, and then the characteristic strain rates in that layer are calculated from the strains and the durations of deformation inferred. The contour map of characteristic maximum compressive strain rates in the lower lithosphere in central-eastern Asia given in the paper shows the strain rates with the magnitude orders of 10^-15～10^-14/s in this region. The strain rates in the plastic-flow belts, which control the seismic activity in the seismogenic layer, are greater than the characteristic strain rates of the network. In addition, the strain rates in the seismogenic layer are influenced also by the factors, involving the directive action of driving boundary along the upper crust, the plastic-flow waves and the existence of the transitional weak layer distributed discontinuously between the upper and lower layers. The comparison between the strain rates in the seismogenic layer and the characteristic strain rates in the lower lithosphere for 11 potential hypocenter areas in the region from the Qinghai-Tibet plateau to North China plain indicates that, except the considerable deviation for the Linfen basin in Shanxi province, the significant linear correlation between the strain rates in the upper and lower layers is shown for all the rest 10 areas by the values of β the ratios which are distributed within the range of 1.25～2.25 with an average of 1.75. It is suggested that the contour map of characteristic strain rates together with the introduction of the ratio β can be used approximately for estimating the strain rates of potential hypocenters in medium- and long-term earthquake prediction and the effects of driving boundaries and relative stable blocks on the hypocentral areas should be considered as sufficiently as possible when taking the values of the ratio β.

Key words: lower lithosphere, seismogenic layer, shallow crust, strain rate, central-eastern Asia

摘要： 根据“网状塑性流动”大陆动力学模型,岩石圈的变形方式由浅层脆性向深层延性的转变以及岩石圈下层网状塑性流动的控制作用,导致板块内部的多层构造变形。GPS方法或断层错动反演方法所测定的只是浅表地壳。多震层的应变速率可用“地震复发间隔法”,根据先后两次地震的复发间隔和后发地震的发震概率予以估计。基于岩石圈下层塑性流动网络共轭角与挤压变形之间的关系,可运用“共轭角法”估计该层的应变,并结合对于变形时间的估计,进一步推算网络的特征应变速率。文中给出了亚洲中东部地区岩石圈下层特征应变速率的等值线图,其数量级为10^-15～10^-14/s。控制多震层地震活动的主要是塑性流动网带,其应变速率大于网络的特征应变速率,除此以外,多震层的应变速率还受到驱动边界的直接作用、塑性流动波和上下层之间非连续分布软弱层的影响。根据青藏高原至华北平原11个潜在震源区所在地段多震层应变速率与岩石圈下层特征应变速率的对比分析,除临汾盆地1处偏差较大外,其余10处两者间表现出显著的线性相关,其比值β平均为1.75,分布范围为1.25～2.25。文中建议在进行中长期地震预测时,可根据岩石圈下层特征应变速率等值线图,结合比值β的引入,粗略地估计各潜在震源区的应变速率;同时,在β的取值上,尽可能地注意到驱动边界和相对稳定地块对该处各地段的影响。

关键词: 岩石圈下层, 多震层, 浅表地壳, 应变速率, 亚洲中东部