KEY TECHNIQUES AND SEVERAL CASES ANALYSIS IN PALEOSEISMIC STUDIES IN MAINLAND CHINA(4) —SAMPLING AND EVENT ANALYSIS OF PALEOSEISMIC DATING METHODS

doi:10.3969/j.issn.0253-4967.2014.04.001

Abstract

Abstract:

Lowering uncertainties of paleoseismic data is very important, which facilitates medium and long-term earthquake prediction and seismic risk assessment in paleoseismic studies. Among these uncertainties, paleoseismic timing is highly focused and its constraint is one of the most key factors in lowering uncertainties. To get the age as true as possible, choosing right dating, sampling methods and techniques on event ages are essential. Among the several primary dating techniques, radiocarbon dating is prior to the other methods. We should choose material that is breached completely during transportation for OSL dating, and samples that are hardly affected by kinds of factors for ¹⁰Be dating. Sampling at appropriate sites based on analysis of tectonic background and using sequential ages to constrain paleoseismic events are the primary keys of techniques on accurate event dating. Interval value is suggested for age constraint when using stratigraphic chronology. When there are multiple ages for different samples within a layer, we should choose the youngest and reliable age. These rules are recommended when constraining paleoseismic ages at a single site. Temporal and spatial correlation such as successive limit method, Z statistics, overlapping distributions likelihood approach, event window and ad hoc weighted overlap methods are the primary analysis approaches for event dating at multiple sites along faults or fault segments.

Key words: paleoseismology, dating technique, samples collection, event analysis

摘要：

古地震资料要在地震中长期预报和地震危险性评估中发挥更重要的作用, 关键在于减小古地震研究中的不确定性, 古地震发生年代的确定是最大限度减小不确定性的关键因素之一.要得到尽可能接近真实的古地震事件年代, 除正确地选择测年方法外, 正确的采样方法和事件年代确定技术尤为关键.在几种主要测年技术中, 优先采集碳十四(¹⁴ C)测年样品、释光样品采集搬运过程有充分 "退火"条件的物质、铍十(¹⁰Be)样品应采集各种干扰因素较少的样品、依据构造运动属性选择适宜的采样位置、用序列样品限制事件年代等, 是正确采集测定事件年代样品的技术要点;用地层年代限制的事件发生年代宜用区间值、有多个可信样品年龄值时应用年轻样品的年代数据, 是确定单一地点事件发生年代的基本原则;而包括逐次限定法、Z统计法、年龄分布曲线重叠法、事件窗法、年龄分布曲线权重重叠法在内的时间对比法, 以及空间对比法是断层或断层段多个测年地点事件年代估计的主要分析方法.

关键词: 古地震, 定年技术, 样品采集, 事件分析

CLC Number:

P597⁺.3

RAN Yong-kang, WANG Hu, YANG Hui-li, XU Liang-xin. KEY TECHNIQUES AND SEVERAL CASES ANALYSIS IN PALEOSEISMIC STUDIES IN MAINLAND CHINA(4) —SAMPLING AND EVENT ANALYSIS OF PALEOSEISMIC DATING METHODS[J]. SEISMOLOGY AND GEOLOGY, 2014, 36(4): 939-955.

冉勇康, 王虎, 杨会丽, 徐良鑫. 中国大陆古地震研究的关键技术与案例解析(4) ——古地震定年技术的样品采集和事件年代分析[J]. 地震地质, 2014, 36(4): 939-955.

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