【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,跨川西北高原及其与四川盆地过渡带的高山峡谷区。由其南东侧边界活动断裂即龙门山北东向活动断裂带,北侧边界活动断裂即西秦岭近东西向构造带的南缘活动断裂带,断块内部近南北向岷山隆起断裂带的岷江与虎牙断裂等活动断裂带组合,构成了本区由西向东逐渐收敛的平卧“A”字形活动构造体系。在该活动构造体系的控制和强大的近东西向构造应力场的驱动下,川西北断块沿两侧边界活动断裂向东强力楔入,于武都、文县-平武、青川“构造急剧收口带”之西侧,沿东经104°线附近形成了一个近南北向展布、地跨三大构造单元的统一强震活动带。而在该带的东、西两侧地区,地震活动则明显减弱。强震沿该带有规律地南、北往返迁移和重复发生。更多还原

【Abstract】 The east part of the inverted-triangle-shaped fault block in the northwest of Sichuan is situated in the northeast edge of the Qingzang Plateau. It extends across the northwest plateau of Sichuan and the valley of transitional area between that and Sichuan Basin. The NE-directional active rift zone of the Longmen Mountains is the southeastern boundary active rift zone of the east part of the inverted-triangle-shaped fault block in the northwest of Sichuan. The recent EW-directional active rift zone of the southern margin of the west of Qinling Mountains is its northern boundary active rift zone. The Minjiang River faults and Huya faults which consist of the recent SN-directional active rift zone of the Minshan Mountains are situated inside the east part of the northwest fault block of Sichuan. The three active rift zones consist of A-type active tectonic system controlling earthquakes. The authors discover the seismic activity law of this region. Generally speaking, inlensive seismic activity belts formed near 104°E . 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 the time, the active period and dormant period alternate and the earthquake whose magnitude is larger than 7.0 tends to accelerate.更多还原