小鱼洞地震地表破裂带罗元村探槽剖面揭示了汶川8.0级大地震之前的1次同等规模的古地震事件.文中对采自小鱼洞破裂带罗元村古地震探槽的7个冲洪积物样品进行了细颗粒石英简单多片再生法和单测片再生法光释光测年研究.LED08-212样品SAR法预热坪实验表明预热温度坪区间为180～240℃,在此温度下热转移量小于等效剂量的1%,不影响测量结果.循环比、回授、剂量恢复试验也表明采用200℃预热温度、10s预热时间和SMAR法流程进行等效剂量测量是合适的,能有效地校正测量过程中的释光信号感量变化.样品LED08-113,LED08-212细颗粒石英SAR法等效剂量值与SMAR法结果的一致性,表明2种方法均适用于本批样品.整个剖面上下盘各形成1个很好的时间序列,结合该地区的历史地震记录,推测小鱼洞断层上次大地震发生的时间应该为距今1.7～2.2ka,其全新世垂直滑动速率至少为(1.0±0.08)mm/a.%In historical records, no earthquake of magnitude comparable with that of the Wenchuan MS 8.0 earthquake has ever been reported in Chengdu and Longmenshan regions. The penultimate event similar to the 12 May 2008 MS 8.0 was revealed by the surface ruptures in the vicinity of Xiaoyudong. It is important, therefore,to date accurately when the prior large earthquake happened. This paper presents 7 optically stimulated luminescence (OSL)ages from Xiaoyudong trench. We investigate the use of simplified multiple aliquot regenerative-dose (SMAR)protocol and single aliquot regenerative-dose (SAR) protocol from fine-grain quartz to date deposits associated with earthquake. The results of SMAR and SAR protocols are consistent. The behavior of quartz to different internal consistency checks of SAR protocol (preheat plateau, thermal transfer, recycling ratio, recuperation and growth curves)and of SMAR protocol(dose recovery)used for the dose estimation method was satisfactory.Various internal consistency tests of the measurement protocols indicate that the dose estimates from the fine grain quartz are accurate and the optical ages are reliable. The preliminary OSL ages indicate that the last large earthquake happened between 1.7 ～ 2.2ka and the slip rate of Xiaoyudong Fault was 1.0±0. 08mm/a at least in Holocene.
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