青海玉树断裂带地震落石的地震地质意义

    A tentative discussion on the seismic and geological significance of the seismic rockfall along the Yushu faulted zone in Qinghai Province

    • 摘要: 2010年青海玉树Ms 7.1级大地震引发了一系列次生地质灾害,其中地震落石是除地震滑坡外沿断裂带及其邻侧最常见的现象。对玉树震区落石的调查发现,该区多处存在非常典型的多期地震落石分布现象,指示该区地震落石的发育与其他古地震现象类似,具有多期性和一定的原地复发性。实地调查表明,该区地震落石分布的主要特征为:多集中发育在活动断裂带附近的陡峭基岩斜坡下方,分布零散,且滚动较远,并常与古地震滑坡相伴生。初步获得的8个地震落石钙膜U系测年结果分布在距今6030±300a BP、4720±210a BP、3530±490~3560±280a BP、2010±160a BP、1090±70a BP、760±20a BP和230±20a BP年龄段,与该区古地震探槽和滑坡反映的地震事件比较吻合,进一步揭示玉树断裂带附近在全新世中晚期发生过多期可导致地表产生地震落石的事件。同时也说明,地震落石及其钙膜测年是特别值得进一步探索的潜在古地震研究方法或途径。

       

      Abstract: In 2010, Ms 7.1 earthquake in Yushu ,Qinghai Province triggered a series of secondary geological disasters, in addition to the earthquake landslide, distribution of seismic rock fall along the fault zone and its adjacent side is extremely common. By the investigation of rockfalls in Yushu area, the survey indicated in a number of typical rockfall zone, in addition to the fresh rockfalls formed in the 2010 earthquake, there are still a lot of early seismic rockfalls scattered, which suggests that the development of seismic rockfall is similar to paleo-earthquake activity, with multi-period and a certain number of in-situ recurrent. The typical seismic rockfall survey found that the distribution characteristics of rockfall is mainly: general concentrated distribution below steep rock slopes near the active fault belt, scattered distribution, rolling far away, and often accompanied by paleo-earthquake landslide.Preliminary U series dating result of 8 seismic rockfalls calcium membrane, distributed in 6030±300a BP, 4720±210a BP, 3530±490~3560±280a BP, 2010±160a BP, 1090±70a BP,760±20a BP and 230±20a BP before present, this result tallies with the seismic events reflected by paleo-earthquake trench and paleo-earthquake landslide well, further reveals the Yushu fault zone occurred multi-period events in the Holocene middle-late leading to the surfacial seismic rockfalls. It also shows that seismic rock fall and calcium membrane dating is a potential and especially worthy way to further explore for the paleo-earthquake research.

       

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