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飑线对定点地形变观测的影响特征与机理——以陕西关中盆地为例
杨小林1,2, 危自根1, 杨锦玲3, 王党席2
1.中国科学院测量与地球物理研究所, 武汉 430077;2.陕西省地震局, 西安 710068;3.福建省地震局, 福州 350003
摘要:
2013年7月31日~8月1日陕西关中盆地爆发了一次强飑线灾害性天气过程,为揭示此次飑线生命史期间对定点地形变观测的影响特征与机理,本文结合多普勒天气雷达和气象资料,系统分析了关中盆地内4个地形变观测数据。结果表明:①飑线过境时的短时气压突变是造成定点地形变的主要原因,引起最大的地倾斜和地应变分别达9.70×10-3"和21.02×10-9;②气压变幅与地形变的弹性响应量具有较好的线性关系,二者持续时间较一致,为2~4h,其中,钻孔体应变的动态气压系数达4.04×10-9/hPa;③宝鸡、乾陵和华阴台对飑线的响应能力较好,西安台则较差;④除水管仪外,垂直摆、洞体应变和钻孔体应变等对飑线的响应均较为灵敏。上述结果有助于合理识别和科学推定飑线所导致定点地形变异常变化的物理本质,进而减少实际业务中的误判;同时,还能为定点地形变观测台站的科学选址、仪器的优化布设及不同空间尺度大气负荷模型的实证等提供重要的参考依据。
关键词:  飑线  强对流天气  气压  定点地形变  关中盆地
DOI:
分类号:P315
基金项目:国家自然科学基金(41604056)、地震科技星火计划(XH18023Y)共同资助
Ground Deformation Induced by a Strong Squall Line: A Case Study in the Weihe Basin, Shaanxi Province
Yang Xiaolin1,2, Wei Zigen1, Yang Jinling3, Wang Dangxi2
1.Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China;2.Shaanxi Earthquake Agency, Xi'an 710068, China;3.Fujian Earthquake Agency, Fuzhou 350003, China
Abstract:
During 31 July to 1 August 2013,a severe squall line crossed the Weihe Basin,Shaanxi Province,which caused hazardous weather. The aim of this work is to investigate the influence characteristics of squall line on the measurements of fixed-point crustal deformation in detail,and to improve our understanding of atmospheric pressure loading signals in pendulum tiltmeter,watertube tiltmeter,extensometer and borehole dilatometer observations during the passage of the squall line. In this paper,we systematically analyze the tilts and strains with 1-minute resolution of the shallow crust at Baoji,Qianling,Xi'an and Huayin observatories induced by the passage of a squall line using the Doppler radar,atmospheric pressure and outdoor air temperature records. The results show that:① The atmospheric pressure jump over a short time span produced by the squall line is the dominant driving force for the pressure-induced crustal deformations. The maximum magnitudes in pressure-induced tilt and strain mostly reach up to 9.70×10-3" and 21.02×10-9,respectively. ② It is observed that the relationship between the variation in amplitude of atmospheric pressure and the magnitude of elastic deformation of shallow crust shows a good linear variation. Their durations are almost the same,which range from 2 to 4 hours. Further,the atmospheric pressure coefficient of crustal deformation can reach up to 4.04×10-9/hPa. ③ The responses of observatories at Baoji,Qianling and Huayin to atmospheric pressure loading are much better than the Xi'an observatory,which implies that the rock cover of Xi'an observatory has low modulus of elasticity. Meanwhile,the effective physical transfer mechanisms for atmospheric loading are strongly influenced by the controlling factors,such as rock integrity,rock strength,cavity and topographic effects. ④ Quasi-synchronous responses of signals in vertical pendulum tiltmeter,extensometer,and borehole dilatometer data to atmospheric pressure loading are very well except for the watertube tiltmeter. The results obtained can be used for identifying and determining reasonably the physical mechanism of anomalous changes in measurements of crustal deformation as a result of squall line aiming to avoid wrong interpretation. Furthermore,the results can contribute to the selection of future observation sites,and give helpful indications for the location of instrument sites promising a low atmospheric pressure influence as well as for evidencing the atmospheric loading models on various spatial scales. In addition,the results also provide the crucial constraints for further numerical modeling with regard to physical transfer mechanisms.
Key words:  Squall line  Severe convection weather  Atmospheric pressure  Fixed-point crustal deformation  Weihe Basin