Plastic-Flow Waves （“Slow-Waves”） and Seismic Activity in Central-Eastern Asia
摘要
The results inferred from experiments with analogue models carried out previously have shown that two types of plastic-flow waves, 'fast-waves' and 'slow-waves', are induced in the lower lithosphere (including the lower crust and lithospheric mantle ) under driving at plate boundaries and both of them are viscous gravity waves formed by the superposition of major and subsidiary waves. The major waves are similar to solitary waves and the subsidiary waves are traveling waves. The plastic-flow waves in the lower lithosphere control seismic activities in the overlying seismogenic layer and result in the distribution of earthquakes along the wavecrest belts. 'Fast-waves' propagated with velocities of orders of magnitude of 100 ～ 102km/a have been verified by wave-controlled earthquake migration, showing the 'decade waves' and 'century waves' with the average periods of 10.8 and 93.4 a, respectively, which originate from the Himalayan driving boundary. According to the recognition of the patterns of the beltlike distribution of strong earthquakes with Ms ≥ 7.0, it is indicated further in this paper that the 'slow-waves' with velocities of orders of magnitude of 100 ～ 101 m/a also originated under compression from the Himalayan driving boundary. Strong earthquakes with Ms ≥ 7.0 are controlled mainly by subsidiary waves, because the major waves with a duration of up to 106 a for each disturbance cannot result in the accmnulation of enough energy for strong earthquakes due to the relaxation of the upper crust. The subsidiary waves propagate with an average wave length of 445 km, velocities of 0.81～2.80 m/a and periods of 0.16 ～ 0.55 Ma. The wavegenerating time at the Himalayan driving boundary is about 1.34 ～ 4.59 Ma before present for the 'slow-waves', corresponding to the stage from the Mid Pliocene to the Mid EarlyPleistocene and being identical with one of the major tectonic episodes of the Himalayan tectonic movement. It is shown from the recognition of the wave-contro