关键词: 岩石圈下层, 多震层, 浅表地壳, 应变速率, 亚洲中东部

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