【摘要】 川西北倒三角形断块东部区域地处青藏高原东部边缘地带,地跨川西北高原及其与四川盆地过渡带的高山峡谷区,属我国著名的南北向地震带的中段,因其特定的大地构造环境和强烈的现代地壳构造运动,导致其在强大的近东西向构造应力场的驱动和平卧“A”字型控震构造体系的控制下,沿两侧边界断裂向东强力楔入,于“构造急剧收口带”之西侧形成了一个近SN向地跨三大构造单元的强震带,强震沿该带有规律的往返迁移和重复发生,且地震活动强弱具有较明显的分形特征。更多还原

【Abstract】 The east part of inverted-triangle-shaped fault block in the northwest of Siehuan is situated in the northwest plateau of Siehuan and the valley of transitional area between that and Sichuan basin, of the northeast edge of Qingzang plateau. Due to its specific tectonic environment and intensive modern crust movement, earthquakes occur frequently.Based on study of geological and seismic data, according to field investigation, fractal analysis,we discover the distribution characteristics and formation mechanism of strong seismic belts in the present in the east part of the triangle fault block and two fault belts in northern and southeastern boundary under recent E-W compress regional tectonic stress-strain field and A-type tectonic system controlling earthquakes; we also discover the seismic activity law of this region. Generally speaking, seismic activity belts located near 104°E. in the form of dense strip. Besides, the frequency and maximum earthquake magnitude inside the fault block are higher than those in boundary faults and the seismic intensity in the north is far larger than that in the south. As far as the space is concerned, intensive earthquakes in 104°E can transfer from boundary faults to those inside and vice versa, when it comes to he time, the active period and dormant period alternate and the earthquake whose magnitude is larger than 7.0 tends to accelerated.更多还原