RECENT PLATE TECTONIC BOUNDARIES AND STRONG EARTHQUAKE BELTS IN EURASIA
欧亚地区现代板块构造边界和强震活动带

The motion patterns occurring along the boundaries between recent pla-tes in Eurasia have a close relation with strong earthquakes there.Recent plate boundaries in Eurasia may be divided basically into three patterns, i. e. underthrusting-colliding, shearing and spreading. These patterns are directly connected with the spatial distributions and strength of plate boundary seismic belts, which is shown in three aspects.1. The seismic belts pertaining to the first pattern possess the largest width and affected area; those pertaining to the second pattern, medium; and those pertaining to the third, the smallest. Within the seismic belts of the same pattern, the affected width may be varied because of different developments of plate boundaries, different subducting angles and the depths of the plates inserted. For the subducting seismic belt, the lower the angle of underthrusting plate is, the deeper the plate is inserted and the wider the belt is, or the narrower in the opposite case. For the seismic belt associated with the collision of plates, the middle stage belt is wider than the later stage one.2. Deep-focus earthquakes occur only in the seismic belts ot the under-thrusting pattern and are same the with most of intermediate-focus ones which have a few in the belt of colliding pattern. In shearing and spreading belts there occur only shallow-focus earthquakes.3. The seismicity in the seismic belts of underthrusting pattern is most violent; that in colliding pattern is less violent and that of spreading pattern is the weakest. The strength of seismicity in different belts of the same pattern are also different on account of their diverse tectonic conditions.