现代强震相关堆积物的释光测年研究有助于理解古地震相关沉积物释光测年的地质意义,提高古地震测年的精度和准确度,更好地认识大地震发生的规律。文中选择了若干典型的2008年汶川大地震的相关堰塞湖堆积物、泄洪堆积物和喷砂堆积物,进行了细颗粒石英光释光测年研究。结果表明,这些地震相关沉积物中的细颗粒石英灵敏度较高,但释光信号并未完全归零,等效剂量残留值有的可高达10Gy,这对百年或千年尺度复发周期地震事件的释光测年影响较大,但对万年至10万年尺度的地质事件测年影响可以忽略不计。地震前古地面附近沉积物样品细颗粒石英的光晒退程度较好,其等效剂量仅0.2Gy,因此应尽量采集古地面附近的样品来限定古地震事件发生的时间。

    The research of optical dating about modern strong earthquake sediments will be useful for understanding geological significance of paleoearthquake related sediments,improving dating precision and accuracy,and better understanding the law of earthquake occurrence.This article chooses some typical sediments related with 2008 Wenchuan earthquake, such as dammed lake deposits,floodwater deposits and ejected sands, to do optical dating of fine-grained quartz.Preliminary results from optical dating of fine-grained quartz extracted from 11 samples suggest that fine-grained quartz is sensitive and D_e values obtained from the three sections indicate residual D_e up to 10Gy. Caution should be taken for optical dating of sediments related to paleoearthquake with a recurrence interval of hundreds or thousands of years,but the effect can be neglected for the paleoearthquake with a recurrence interval of ten thousands or hundred thousands of years.Residual D_e values less than 0.2Gy are observed in two samples collected from pre-earthquake surface.Therefore,we should collect samples on pre-earthquake surface to limit the event time.