利用双差定位方法，对2013年10月—2016年12月乳山震群进行重定位，并计算乳山震群中地震集中活动区域b值，分析其深度分布变化。结果显示：地震重定位后表现为近NW向集中分布；b值在震源深度7.4 km上下最小，反映该深度处应力最强；乳山震群b值并不随震源深度增大而呈系统性减小变化，且深度10.2 km以下无有效b值，进一步证实该震群近NW向发震断裂的存在。根据b值随深度的变化特征，推测断裂活动的高应力区域集中在6.5—10.2 km深度范围内，断裂活动在深度7.4 km处应力最强，且水平分布最广；相比上下两侧地壳介质b值在5.5—6.2 km深度层位明显增大，反映该深度层位介质性质存在明显差异。
The Rushan earthquake sequence from October 2013 to December 2016 was relocated by using the double difference location method. According to the result of relocation, the variation of b value with depth and the vertical profile distribution of b value of the seismic activity concentrating area in Rushan earthquake sequence is calculated. The results obtained are as follows. The distribution of earthquake sequence concentrated along the NW direction. The variation of b value with depth shows that the b value in 7.4 km depth is the lowest, and the stress at this depth is the most concentrated. The b value of Rushan earthquake sequence does not decrease with the increase of depth, and we cann't calculate the effective b value below 10.2 km depth. This result has verified the existence of the strike-slip fault which along the direction of the NW around the Rushan earthquake sequence. According to the variation of b value with depth, it is inferred that the high stress area of the strike-slip fault is in 6.5-10.2 km depth, the highest stress area of fault concentrated in 7.4 km. And the high stress area of the strike-slip fault near the depth of 7.4 km is the most widespread. The b value is significantly increased in the range of 5.5-6.2 km, and reflects that this depth layer is obviously different from other layers.
2018,39(2): 25-32 收稿日期：2018-01-24
DOI：10.3969/j.issn.1003-3246.2018.02.004
基金项目：山东省地震局合同制科研项目（编号：16Y03，17Y01）；山东省地震局科研基金项目（编号：JJ1601）
作者简介：申金超(1986-),男,硕士研究生,山东临沂人,工程师,主要从事地震监测研究工作。E-mail:sjchao1@163.com
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