摘要
如何阐明(近)地表周年变形的物理机制,一直是地壳形变观测和解释中的一大热点和难点.新疆乌什台钻孔体应变仪自2007年开始观测以来,便能记录到清晰且规律的周年变化,其振幅值高达3.82×10^(-6);那么,这种信号所蕴含的物理机制究竟如何?截止目前,还鲜有针对性的动力学研究.鉴于地表气温年变是造成近地表应变周年变化的一个重要驱动力,加之乌什台地表气温和钻孔体应变年变高度相关;所以,本文依据乌什台2016—2022年的气温年变、钻孔系统和台基介质等实况,并尝试采用含松散盖层(解耦层)半空间热固耦合模型,定量解析了15.44℃的气温年变在75.6m深处所产生的理论热应变变化.结果表明,当解耦层的厚度为2.64m时,理论值的年变振幅和相位皆能与实测值吻合.据此,我们可以合理揭示出乌什台钻孔面应变的周年变化和地表气温年变之间的因果关系.通过对该典型个例的系统剖析,不仅可以提升我们对钻孔应变年变机制的科学理解,而且还能为我国定点地壳形变台网的年变信号研究提供算法参考.
A very challenging but attractive problem in the field of observation and analysis of crustal deformation is how to clarify the dominant source of free-and/or near-surface annual deformations.Since 2007,the borehole volumetric signal observed at Uqturpan station has exhibited significant annual fluctuations with an amplitude of 3.82×10^(-6).However,the physical mechanism underlying this phenomenon remains unclear because of a lack of targeted investigation.To the best of our knowledge,near-surface annual deformation usually results from annual variations in atmospheric temperature.Moreover,the annual variations of air temperature and borehole volumetric strain correlate well with each other for Uqturpan station.Therefore,the annual borehole volumetric fluctuation may result from thermoelastic strain induced by atmospheric temperature variations.Based on the characteristics of the borehole system and rock formation,a composite model with an unconsolidated layer over a half-space was applied to calculate the thermoelastic strains from the atmospheric temperature during 2016—2022.The results showed that an annual temperature change of 15.44℃ can generate thermoelastic strain amplitudes of up to 3.82×10^(-6) at 75.6 m depth.Furthermore,the modeled annual thermoelastic strain with phase can also be fitted well with the observed annual variation if the decoupled layer is equal to 2.64 m.Thus,we can reasonably conclude that the annual variation of borehole areal strain observed at Uqturpan station is mainly caused by atmospheric temperature variation.In summary,the findings may facilitate understanding of the driving mechanism of annual variations in borehole strain data,and the methods used in this study can be applied to quantitatively diagnose the fixed-point strain observatories of crustal deformation in China.
作者
杨小林
李航
杨锦玲
危自根
YANG XiaoLin;LI Hang;YANG JinLing;WEI ZiGen(Minjiang University,Fuzhou 350108,China;Jinggangshan University,Ji′an Jiangxi 343009,China;Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences,Wuhan 430077,China)
出处
《地球物理学报》
北大核心
2025年第6期2216-2229,共14页
Chinese Journal of Geophysics
基金
国家自然科学基金(42104089,42104091)
福建省自然科学基金(2024J08288)
闽江学院科研启动项目(MJY24015)共同资助.
关键词
钻孔面应变
周年变化
气温
热弹性应变
乌什台
地壳形变
Borehole areal strain
Annual variation
Atmospheric temperature
Thermoelastic strain
Uqturpan station
Crustal deformation
