Abstract: Following the 11 March 2011 Japan M_W9.0 earthquake, frequent moderate and small events occurred on the Yishu fault zone and its either side. Using continuous GPS data and a sliding block model, this work studies the relationship between the energy release of these shocks and the block relative motion of either side of the Yishu fault zone. The results show that(1)the equivalent magnitude M from released energy and the two blocks' relative motion are well correlated when earthquakes are selected in a retrieval circle(whose center is the midpoint of the Yishu fault zone)with a radius of 250~500km and using a sliding time window of 3~10 months. The best correlation coefficient between M and the two blocks' relative motion is 0.74 and the T test shows a significant linear correlation between them.(2)Spatial distribution of the correlation coefficients shows that the relative motion of the blocks on both sides affects the energy release in the area from the north part of Yishu fault zone to the Jiaodong Peninsula area and southwest Shandong-Henan border area obviously.(3)Since June 2014, the relative motion of the two blocks on both sides of the Yishu fault zone presents a wave of change, which may be an expression of the accumulation of seismic strain energy in the Yishu fault zone and its two sides. The linear relationship between the equivalent magnitude M from released energy and two blocks' relative motion V can be fitted by linear equation M=0.51*V+3.9, showing that strain energy accumulation could be released by the moderate and small earthquakes in a timely manner, which may favorable to delay the seismic risk in the study area. It also shows, on the other hand, that earthquake energy was not released so completely in the study area since the end of 2015 to 2016, which is likely associated with the Changdao earthquake swarm in 2017.

Key words: Japan M_W9.0 earthquake, Yishu fault zone, active block, block model, earthquake activity, energy release

摘要： 日本M_W9.0地震后沂沭断裂带及其两侧地区中小地震活动频繁。文中利用连续GPS数据和滑动块体模型研究了上述地震活动的能量释放过程与沂沭断裂带两侧块体相对运动过程的关系，为该地区的地震危险性分析提供依据。结果表明：1）沂沭断裂带周围250～500km、时间窗长为3～10月的地震总释放能量折算震级M与两侧块体相对运动呈较好的相关性，最优相关系数为0.74，T检验显示两者显著线性相关；2）两者相关性的空间分布显示两侧块体的相对运动对沂沭断裂带北部至胶东半岛地区及鲁西南—河南交界地区的地震能量释放影响明显；3）研究区总释放能量折算震级M与两侧块体的相对运动速率V呈M=0.51×V+3.9的线性关系，2015年底—2016年研究区存在地震能量积累现象，2017年发生的长岛震群可能与此有关。

关键词: 日本M_W9.0地震, 沂沭断裂带, 块体模型, 地震活动, 能量释放