| 自维持断层蠕滑过程和余震发生率的衰减特征—以汶川MW7.9地震序列为例 |
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| 引用本文： | 解孟雨,史保平,林禄春.自维持断层蠕滑过程和余震发生率的衰减特征—以汶川MW7.9地震序列为例[J].地震学报,2018,40(3):316-331. |
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| 作者姓名： | 解孟雨 史保平 林禄春 |
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| 作者单位： | 中国北京 100049 中国科学院大学地球与行星科学学院 |
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| 基金项目： | 科技部国家国际科技合作专项项目（2015DFA21260）资助 |
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| 摘 要： | 基于Dieterich地震活动性理论，本文推导出计算余震发生率和余震累积次数的一般表达式，其中主震后发震断层内部的剪切应力随时间的演化过程遵从Jeffreys-Lomnitz蠕变模型，且与修正Omori定律直接相关。修正Omori定律中的p值与震后断层的短时应力加卸载过程正相关。采用Rubin和Ampuero 给出的震后断层自维持蠕滑模型本文得出计算余震发生率的近似表达式，并对2008年汶川地震序列进行拟合。结果表明，p值的大小直接对应了速率-状态摩擦定律中摩擦参量b/a，而修正Omori定律中的c值则与速率-状态摩擦定律中的临界滑移Dc相关。对于汶川余震序列而言，拟合结果显示b/a约为1.13，Dc约为2—3 cm。Rubin-Ampuero震后自维持蠕滑描述了震后孕震层内部短暂的速率变化特征，是孕震断层演化过程不可缺少的环节。
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| 关 键 词： | 余震发生率 震后蠕滑 应力 应力加载速率 |
| 收稿时间： | 2017-06-01 |
Aftershock rate decay induced by postseismic creep: A case study from the MW7.9 Wenchuan earthquake sequence |
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| Affiliation: | College of Earth and Planetary Sciences，University of Chinese Academy of Sciences，Beijing 100049，China |
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| Abstract: | Based on the Dieterich seismicity theory, this study derived a general formula used to calculate decay rate and cumulative frequency of aftershocks following a mainshock, of which the shear stress variation in the fault plane follows the Jeffreys-Lomnitz creep law and is directly related to the modified Omori law. The p value in the modified Omori law is positively correlated with post earthquake loading and unloading process of the transient stress. Combined with the postseismic slip model proposed by Rubin and Ampuero, this study obtained approximate formulas to describe the variation of seismicity and to fit aftershock sequence following the 2008 MW7.9 Wenchuan earthquake. The results show that the p value is directly associated with the ratio of b/a, where a and b are the frictional parameters used in rate- and state-dependent friction, and the c value used in the modified Omori law is associated with Dc, a critical creep distance described by rate- and state-dependent friction. For the MW7.9 Wenchuan earthquake sequence, the fitting results indicate the ratio of b/a and Dc are about 1.13 and 2 to 3 cm, respectively. It needs to be emphasized that postseismic creep proposed by Rubin and Ampuero is an inherent stage during earthquake cycle, which describes characteristics of the transient velocity change in seismogenic zone after the mainshock. |
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