汶川地震前的<i>b</i>值变化

doi:10.6038/cjg2018M0024

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摘要 Gutenberg-Richter定理给出了地震频度随震级的分布特征.大量研究表明频度-震级关系的斜率（b值）在大地震孕育的过程中会出现减小.为了考察b值在汶川地震孕育过程中的时间演化特征，本文尝试基于破裂断层选取研究区域，考察了2000年1月至2008年4月间，汶川地震（M_S8.0）破裂区的地震活动性，并对该区域b值的变化进行了探讨.结果表明，在2005年中至2006年底，地震月频度及季度频度有一个较明显的下降.b值从2002年始至地震前呈现出一个长期趋势性减小；在地震前约半年，出现快速、显著的下降.b值的这一时间变化特征与其他研究者报道的日本东北M_W9.0级地震前的b值变化特征具有很高相似性，可能反映了大地震准备过程中的应力变化.以上结果有益于认识和理解大地震孕育演化过程，同时也表明b值在中长期地震灾害评估中具有潜在价值.

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	史海霞
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	韩鹏

关键词 ：汶川地震, b值, 地震活动性, 孕震区

Abstract：The Gutenberg-Richter Law describes the frequency-magnitude distribution of earthquakes. A number of studies have shown that the slope (b value) of the relationship between frequency and magnitude decreased before large earthquakes. Based on the analysis of the earthquake catalog from January, 2000 to April, 2008, we have investigated seismicity change and b value variation prior to the M_S8.0 Wenchuan earthquake. The results show clear drops of both monthly and quarterly frequency of earthquakes during 2005—2006. The b value exhibits a long-term decrease trend since 2002, and reaches to the minimum just before the onset of the main shock. The temporal variation of b value is quite similar to that prior to the M_W9.0 Tohoku earthquake in Japan, which may reflect the stress evolution during the preparation process of large earthquakes. These results indicate that the b value is an important indicator of an impending great earthquake, and has high potential in terms of predicting a future large quake.

Key words： The Wenchuan earthquake b value Seismicity Seismogenic zone

收稿日期: 2018-01-16

PACS:

P315

基金资助:国家自然基金项目（41774069，41404045，41790465）和"重大自然灾害监测预警与防范"重点专项（2017YFC1500304）联合资助.

通讯作者: 韩鹏,男,1985年生,南方科技大学地球与空间科学系助理教授,主要从事地震活动性分析,地震概率预测,及地震电磁学研究.E-mail:hanp@sustc.edu.cn E-mail: hanp@sustc.edu.cn

作者简介: 史海霞,女,1980年生,中国地震台网中心,高级工程师,主要从事地震活动性研究工作.E-mail:shihaixia08@seis.ac.cn

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http://manu39.magtech.com.cn/Geophy/CN/10.6038/cjg2018M0024 或 http://manu39.magtech.com.cn/Geophy/CN/Y2018/V61/I5/1874

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