Analysis of Gravity Variation and Vertical Crustal Deformation at Wuhan Jiufeng Seismic Station
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摘要: 长期的重力变化和地壳形变观测是研究地下物质运动的重要手段。基于武汉九峰地震台2013—2020年的绝对重力和全球卫星导航系统(global navigation satellite system,GNSS)观测数据,计算了长期的重力与地壳垂直形变的变化趋势,并以1年、2年和3年的时间间隔分段,进行线性趋势拟合,分别获得不同时间段的绝对重力年变化率、地壳垂直形变速率以及对应的比值。研究结果表明,武汉九峰地震台长期的重力年变化率为0.479 9 μGal/a,地壳垂直形变速率为-1.2 mm/a, 两者的比值为-0.399 9 μGal/mm,与理论值存在一定的偏差,可能与该区域的地下水活动有关。将不同时间段的重力变化与地壳垂直形变的数据展布在一张图中,发现数据点离散分布在不同区域,由此可初步判断地下物质运动过程,为区域动力学机制解释提供参考。Abstract:Objectives Long period observation of gravity variation and crustal deformation is one of the important means to study the movement of underground material. However, long-term monitoring of regional material migration law is rarely carried out.Methods Based on the absolute gravity and global navigation satellite system (GNSS) observation data of Wuhan Jiufeng seismic station from 2013 to 2020, we calculate the variation trend of long-period gravity and vertical crustal deformation. The linear fitting trend is carried out at the intervals of 1 year, 2 years and 3 years, and the annual change rate of absolute gravity, vertical crustal deformation and the corresponding ratio in different time periods are obtained.Results The results show that the long-term gravity change rate of Wuhan Jiufeng seismic station is 0.479 9 μGal/a, the vertical crustal deformation is -1.2 mm/a, and the ratio is -0.399 9 μGal/mm. There is a certain deviation from the theoretical value, which may be related to the groundwater activities in this area. It is found that the data points are discretely distributed in different regions and close to the theoretical value.Conclusions Through the study of the long-term trend of gravity change and crustal deformation and the distribution map of different periodic data, the process of underground material movement can be preliminarily judged, which provides an important reference for the interpretation of regional dynamic mechanism.
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致谢: 感谢武汉九峰地震台、国家重力台网中心、中国科学院精密测量科学与技术创新研究院、中国地震局GNSS数据产品服务平台提供的数据支持和帮助。
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表 1 重力与形变的计算结果
Table 1 Calculation Results of Gravity and Deformation
时间间隔 观测时间 绝对重力年变化率/(μGal·a-1) 地壳垂直形变速率/(mm·a-1) 比值/(μGal·mm-1) 1年 2013-06—2014-04 -5.7 5.7 -1.00 2014-04—2015-05 12.1 7.3 1.65 2015-05—2016-05 -1.0 -1.1 0.91 2016-05—2017-06 -7.8 -2.2 3.54 2017-06—2018-01 7.3 4.8 1.52 2018-01—2019-04 0.6 4.3 0.14 2019-04—2020-11 -2.0 -1.6 1.25 2年 2013-06—2015-05 4.7 -1.6 -2.93 2014-04—2016-05 6.7 -3.7 -1.81 2015-05—2017-06 -5.0 -2.1 2.38 2016-05—2018-01 -2.1 -6.9 0.30 2017-06—2019-04 2.9 6.6 0.44 2018-01—2020-11 -0.9 5.7 -0.16 3年 2013-06—2016-05 4.0 -3.2 -1.25 2014-04—2017-06 1.1 -4.3 -0.25 2015-05—2018-01 -2.4 -4.3 0.55 2016-05—2019-04 -0.2 1.9 -0.10 2017-06—2020-11 0.6 6.4 0.10 -
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