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鲜水河断裂作为青藏高原东南部现今运动最为强烈的活动构造,因历史上一系列大震(如1786年康定7级地震、1816年炉霍7级地震和1973年炉霍7.6级地震等)的发生而一向备受关注。本文基于跨越鲜水河断裂道孚段和干宁段的两条密集型GPS剖面自2005年以来的高精度地壳运动观测资料(其中4站为连续GPS观测,23站为每年一期的非连续GPS观测),揭示出鲜水河断裂在汶川8.0级地震之前,一直保持着强烈而稳定的左旋(~10.4±1.0mm/a)兼轻微拉张(~0.3±1.2mm/a)运动。汶川地震的发生,使鲜水河断裂干宁段和道孚段近断层两侧分别发生了量值达13mm和4mm的侧向拉伸,并使干宁—道孚段发生了量值达2.5~10mm的右旋位错,因此,对其现今的左旋运动方式施加了短暂的反向抑制,但汶川地震后,鲜水河断裂的运动状况很快恢复了以往的态势。我们的研究结果表明,汶川地震的发生,使鲜水河断裂的应变积累有所消减,故在一定程度上降低了该断裂未来的地震危险性水平。另外,青藏高原东南部的GPS速度场和鲜水河断裂两侧的应变分析显示,鲜水河断裂所表现的强烈左旋差异运动是由其南侧“流滑带”的东南向逃逸远大于北侧松潘地块的轻微东南向运动所致。
Because of a series of major earthquakes in history (such as the Kangding MS7 of 1786, the MS7 of 1816 and the MS7.6 Hearthquake of 1973) Has always been the concern. Based on observations of high-precision crustal movement over two intensive GPS profiles covering Daofuhe and Qianning of the Xianshuihe fault since 2005 (four of which are continuous GPS observations and 23 are non-continuous GPS observations) revealed that the Xianshuihe fault had a strong and stable left-handed (~10.4 ± 1.0mm / a) and slight tension (~0.3 ± 1.2mm / a) movements before the Wenchuan Ms8.0 earthquake. The occurrence of the Wenchuan earthquake resulted in lateral stretching of 13mm and 4mm on both sides of Qianning section of Daoshuihe fault and Daofu section, respectively, and the magnitude of Ganning-Daofu section reached 2.5 ~ 10mm dextral dislocation. Therefore, a brief reverse suppression is applied to the current left-lateral movement. However, the movement of the Xianshuihe fault quickly restored the previous trend after the Wenchuan earthquake. Our results show that the occurrence of the Wenchuan earthquake reduces the strain accumulation in the Xianshuihe fault and therefore reduces the future earthquake risk to a certain extent. In addition, strain analysis on both sides of the GPS velocity field and the Xianshuihe fault in the southeastern part of the Qinghai-Tibet Plateau shows that the strong left-difference movement represented by the Xianshuihe fault is largely caused by the southeastward easing of the south side of the “slippery zone” Caused by slight southeast movement of the Songpan block on the north side.