2016年度呼图壁地下天然储气库对周缘微地震活动性的影响

Effects of the Hutubi underground gas storage in 2016 on the surrounding seismic activities

呼图壁储气库是中国目前存储量最大的天然气储气库,位于新疆准噶尔盆地南缘,北天山山前坳陷带内的呼图壁背斜上.储气库靠近百万人口大城市乌鲁木齐,气库的注放气活动对其周缘地震活动的长期影响是事关生产和生活的重要安全问题.本文以呼图壁储气库为中心,在86.5°E—87.5°E,43.5°N—44.5°N的范围内,基于新疆维吾尔自治区地震局在该区域建立的密集流动台阵数据,应用模板匹配滤波技术对2016年全年的波形数据进行搜索识别,检测到遗漏地震事件151个,完善扩充了原有地震目录,使得该区域完备震级由1.1降到约0.7.通过分析新目录中404个地震的时空分布规律,我们发现2016年,即气库建成第三年以后,储气库的气压变化依然会影响周缘地区的地震活动.当储气库的气压增大到超过约22 MPa的阈值后,较小的气压波动也会导致该区域地震活动性明显增强;气压变化对距储气库中心最远约40 km范围内区域的地震活动存在较为明显的影响.

The Hutubi underground gas storage(HUGS)is the largest of its kind so far in China,it is located in the front of the northern Tianshan depression and the southern margin of Junggar Basin in Xinjiang.The HUGS is close to the large city Urumqi with more than 3.5 million population,its operation and possible influence on the seismicity in the surrounding area poses an important issue to both the safety of industrial activities and human life.We investigate the seismicity within an area centered in HUGS in the range of 86.5°E—87.5°E,43.5°N—44.5°N.Based on the data from a dense transportable array in this area deployed by the Xinjiang Uyghur Earthquake Administration,we use the matching filtering method to scan the waveform data of the year 2016 and detect 151 missing earthquakes,successfully expand the earthquake catalog to 404 events and reduce the magnitude of completeness from 1.1 to about 0.7.Temporal and spatial analysis shows that the pressure of the HUGS probably has a positive influence on seismicity in the adjacent area.When the pressure increases beyond a certain threshold about 22 MPa,the seismicity in the area becomes more sensitive to the fluctuation of the pressure,even a small perturbation of pressure can trigger earthquakes in the surrounding area.The influence is significant within the 40 km range of the HUGS and phases out with distance.