关键词: 岩石圈, 塑性流动波, “慢波”, 地震能量背景, 强震, 亚洲中东部

Abstract: The results inferred from the experiments of analogue modeling carried out previously have shown that two types of plastic-flow waves, "fast-wave" and "slow-wave", are induced in the lower lithosphere (including the lower crust and lithospheric mantle) under the driving at plate boundary; and both of them are the viscous gravity waves formed by the superposition of major and subsidiary waves. The major one is similar to solitary wave and the subsidiary one is traveling wave. The plastic-flow waves in the lower lithosphere control the seismic activities in the overlying seismogenic layer and result in the distribution of earthquakes along the wave-crest belts. The "fast-waves" propagated with velocities in the orders of magnitude of 10⁰～10²km/yr have been verified by the wave-controlled earthquake migration, showing the "decade waves" and "century waves" with the average periods of 10.8 and 93.4yr, respectively, which are originated from the Himalayan driving boundary. According to the recognition of the patterns of the belt-like distribution of strong earthquakes with M_S≥7.0, it is indicated further in this paper that the "slow-waves" with velocities in the orders of magnitude of 10⁰～10¹m/yr are also originated under the compression from the Himalayan driving boundary. The strong earthquakes with M S≥7.0 are controlled mainly by the subsidiary waves, because the major waves with the duration up to 10⁶yr for each perturbation are impossible to result in the accumulation of energy enough for generating strong earthquakes owing to the relaxation of the upper crust. The subsidiary waves propagate with an average wave length of 445km and, as estimated in term of the requirement of elastic energy for strong earthquakes in the crust (the constraint of energy for strong earthquakes) and the actual situation of the apparently immobile wave-crest belts (the constraint of the relative immobility of wave-crest belts), with velocities of 0.81～2.80m/yr and periods of 0.16～0.55Ma. The wave-generating time at the Himalayan driving boundary is about 1.34～4.66Ma BP for the "slow-waves", corresponding to the stage from Mid Pliocene to Mid Early-Pleistocene and being identical with one of the major tectonic episodes of the Himalayan tectonic movement. It is shown from the recognition of the wave-controlled belts of strong earthquakes that two optimal patterns of wave-crest belts are originated simultaneously from the eastern and western segment of the Himalayan arc, respectively. The overlap of wave-crest belts of these two systems are responsible for the relative concentration of energy and the formation of the seismic-energy-background zones for strong earthquakes with M_S≥7.0.

Key words: central-eastern Asia, lithosphere, Plastic-flow wave, "slow wave", seismic-energy-background zone, strong earthquake