探槽古地震事件识别标志及其定量化——以活动走滑断裂为例

    Paleo-earthquake evidence and its quantitative evaluationin trenches:Exemplified by active strike-slip faults

    • 摘要: 探槽古地震事件的识别取决于对沉积地层中封存的构造变形和沉积响应的解译。基于国内外88篇走滑断裂古地震研究论文,系统总结分析了古地震事件的多种识别标志,主要包括地层的垂向错断、断层向上逐渐尖灭、生长地层、裂缝充填、角度不整合、砂土液化、崩积楔、褶皱等。这些识别标志的质量和数量是判别古地震事件的关键。综合分析认为,地震成因识别标志与非构造成因及蠕滑产生的变形不同,而不同识别标志对地震层位的限定有证据强弱之分。在充分考虑地域和人为因素的影响下,根据识别标志的强弱,对探槽揭露事件的地层证据进行半定量化分析,这在实际工作中不仅可以最大限度地降低误判地震事件的可能性,排除非地震成因变形的影响,也能更客观地反映地震事件的可信度。

       

      Abstract: Identification of paleo-earthquake events in trench depends on the interpretation of the structural deformations and associated sedimentary responses preserved in the sedimentary strata. Based on 88papers of paleoseismic studies of strike-slip fault published in China and abroad, the authors systematically summarized the empirical paleoseismic indicators, which includes vertical offset, upward termination of fault, growth strata, infilled fissures, angular unconformities, liquefactions, colluvial wedges and folds. The quality and frequency of these event indicators constitute the key to distinguishing paleoseismic events and event horizons. Ground deformation caused by non-structuralfactor and creepingis slightly different from eventindicators.In practice, the semiquantitative methodcan minimize the influence of non-seismic genetic deformations, reduce the risk of misestimating of paleoearthquake events, and give an objective event confidence level.

       

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