What causes the remarkable tilt anomalies at the Hancheng geodynamic observatory in Shaanxi Province?
-
摘要: 巨幅地倾斜异常既可能是地震前兆异常信息,也有可能是仪器问题或环境干扰所致的异常信号. 有效地厘清其性质,对地震前兆异常的及时识别与科学判定至关重要. 陕西韩城台金属水平摆EW分量自2010年以来连续两次出现巨幅东倾和西倾异常,幅度分别约达140″和180″,该巨幅地倾斜异常产生的根源至今尚未被厘清. 鉴于此,本研究依据韩城台所在区域的水文、构造和地震活动等特征,提出并分析了地下水动力变化、韩城断裂慢滑移和地壳应力场变动等3种可能的成因机制. 结果表明,第一种成因机制难以有效地解释巨幅地倾斜异常,第二和第三种成因机制则具有一定的可能性,但证据还不够充分. 因此,更可靠的物理解释尚需更多的观测和更深入的研究. 尽管本文未能给出该巨幅异常的真正成因,但所采取的分析方法可为今后巨幅地倾斜异常性质的判定工作提供有益的参考.Abstract: The remarkable tilt anomalies could be the earthquake precursors, but may also be caused by instrumental factors and environmental disturbances. Thus, the question arises on how to distinguish the earthquake precursors from the non-tectonic factors, which is very important to effectively and reasonably detect earthquake precursors. Since 2010, two remarkable tilt anomalies have been recorded by metallic horizontal pendulums in E-W component at the Hancheng observatory in Shannxi Province, and the amount of east- and west-ward tilt approxi-mately reach up to 140″ and 180″, respectively, but these two remarkable tilt anomalies have not been reasonably and clearly interpreted till now. Here, we propose and compare three different causal mechanisms possibly responsible for these anomalous phenomena according to the regional hydrological, tectonic and seismicity characteristics, i.e. ① hydrodynamics-induced surface tilt, ② a long-term slow slip event on the northeastern segment of the Hancheng fault, and ③ variations of the regional tectonic stress field during the anomalous period. We then theoretically calculated the poroelastic deformation and the fault slip amount, and finally inversed the focal mechanism solutions of 85 earthquakes (2.0≤ML≤4.8) that occurred between 2008 and 2015 with the aim of determining the regional stress field changes (35°N—36°N, 110°E—111°E) in the crust. Our results show that the first possibility can be shown unlikely, but it is difficult to rule out the second and the third possibility according to the current eviden-ce. To further prove and confirm the causal relationship between deformation of tectonic origin and the anomalies, more comprehensive tilt and crustal deformation measurements are necessary in the Hancheng region in the future, furthermore, more intensive researches are also needed to reveal and determine the causal mechanisms of these anomalies. Unfortunately, we fail to find the real causal mechanism, but the approaches used in this study could be helpful to investigate the causal origin of remarkable anomalies recorded by tiltmeters in the near future.
-
引言
确定输入地震波是结构抗震工程领域进行时程动力分析过程中的一个重要课题,目前国内外使用比较广泛的方法是根据设计反应谱来拟合匹配的人工地震波,将其作为抗震设计的输入地震波。为了满足某些特定的地震动工程特性,如时域、频域信息等,按照一定的数值算法合成地震动时程的过程即为地震动的反应谱拟合。
反应谱拟合分为时域法和频域法两种(刘帅等,2018)。时域法是通过时域内某个特定点的脉冲来调整反应谱上某点发生的最大位移,例如使用窄带时程叠加法(赵凤新,张郁山,2007;何佳,王海涛,2010)或小波变换来拟合地震动(白泉等,2015;Cecini,Palmeri,2015;谢皓宇等,2019),以及使用Broyden算法的地震动拟合方法(Adekristi,Eatherton,2015)。时域法更多是在已有某地震动的条件下,通过修正地震波的时域分量使其反应谱向设计谱逼近,而频域法则不需要自然波或者其它地震波作为必要条件,仅通过一个随机相位谱即可生成人工地震波(陈永祁等,1981;Gupta,2002),因此频域法拟合人工地震波的随机性高于时域法。
然而,传统的频域法拟合人工地震动在计算过程中并未区别傅里叶谱各频率分量对最大反应的贡献为正或负,也未涉及随机相位谱对于拟合结果的影响,这造成了算法的迭代效率偏低、拟合的频域顽固点较多等问题。因此,亟需研发一种改进的人工地震波拟合方法。
鉴于此,本文在传统的频域法拟合人工地震动的基础上,提出考虑每次迭代的相关性,区别傅里叶谱各频率分量对最大反应的贡献的正负,并对随机相位谱进行修正的一种新的综合方法,以期提高拟合精度,加快计算速度。
1. 频域法拟合人工地震波
频域法的基本原理是通过具有随机相位谱的一组三角函数的叠加来构造一个近似的平稳高斯过程,再乘以一个等时程的包络函数,最终得到一个非平稳的加速度时程(杨庆山,姜海鹏,2002)。频域内拟合人工地震波并使用迭代调整幅值谱的方法主要包括以下几部分:
1) 使用单阻尼反应谱与频谱(功率谱密度函数)之间的近似转换关系(Kaul,1978),将目标反应谱转换为相应的功率谱密度函数。通常使用的近似转换关系为
$ {S_{{{\!\!\ddot x}_0}}}\!\!\!\!\!{\text{(}}{{\omega _k}} {\text{)}}\!\!\!\! {\text{=}} \frac{\textit{ξ} }{{{\rm{\pi }}{\omega _k}}}[S_{\rm{a}}^{\rm{T}}\!\!\!\!{\text{(}}{{\omega _k}} {\text{)}}\!\!\!\!]^2 \cdot {\left\{ { {\text{-}} \ln \left[ {\frac{{ {\text{-}} {\rm{\pi }}}}{{{\omega _k}T}}\ln \!\!\!\!{\text{(}}{1 {\text{-}} \gamma } {\text{)}}\!\!\!\!} \right]} \right\}^{ {\text{-}} 1}} {\text{,}} $
(1) This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
2) 将得到的功率谱密度转化为傅里叶幅值谱:
$ {A}^{2}\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\!{\text{=}} 4{S}_{{ \!\!\ddot{x}}_{0}}\!\!\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\!\cdot \Delta \omega {\text{,}} $
(2) 式中,A(ωk)为傅里叶幅值谱,Δω为频域采样间隔。
3) 基于通过步骤2)计算所得的傅里叶幅值谱,再引入随机相位谱,使用三角函数的叠加或者快速傅里叶逆变换将得到的傅里叶幅值谱转换为零均值的平稳高斯过程:
$ {\tilde x}_{0}\!\!\!\!{\text{(}}t{\text{)}}\!\!\!\!{\text{=}} \sum\limits_{k {\text{=}} 1}^N A\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\!\sin\!\!\!\!{\text{(}}{\omega }_{k}t {\text{+}}{\varphi }_{k}{\text{)}}\!\!\!\!{\text{,}} $
(3) $ {{\tilde x}_0}\!\!\!\!{\text{(}}t {\text{)}}\!\!\!\! {\text{=}} {\rm{FF}}{{\rm{T}}^{ {\text{-}} 1}}\left[ {A\!\!\!\!{\text{(}}{{\omega _k}} {\text{)}}\!\!\!\!{{\rm{e}}^{{\rm{i}}{\varphi _k}}}} \right]{\text{,}} $
(4) This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
式(3)与式(4)所对应的两种方法最后的合成结果几乎一致,不同之处在于:快速傅里叶变换的计算速度更快,但对反应谱采样和插值有一定要求;利用三角函数叠加的计算速度较慢,但计算过程中的限制更少。
This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
$ {\ddot{x}}_{{\rm{a}}}\!\!\!\!{\text{(}}t{\text{)}}\!\!\!\! {\text{=}}I\!\!\!\!{\text{(}}t{\text{)}}\!\!\!\!\cdot {\tilde x}_{0}\!\!\!\!{\text{(}}t{\text{)}}\!\!\!\!{\text{,}} $
(5) $ I\!\!\!\!{\text{(}}t {\text{)}}\!\!\!\! {\text{=}} \left\{ {\begin{array}{*{20}{l}} {{{\left( {{\dfrac{t}{{{t_1}}}} } \right)}^2}}&\qquad{0 {\text{<}} t {\text{≤}} {t_1}}{\text{,}}\\ 1&\qquad{{t_1} {\text{<}} t {\text{≤}} {t_2}}{\text{,}}\\ {\exp [{ {\text{-}} c({t {\text{-}} {t_2}} })]\!\!\!\!\!}&\qquad{{t_2} {\text{<}} t {\text{≤}} T}{\text{,}} \end{array}} \right. $
(6) This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
$ {A}_{n {\text{+}}1}\!\!\!\!{\text{(}}\omega_{k}{\text{)}}\!\!\!\!{\text{=}}{A}_{n}\!\!\!\!{\text{(}}\omega_{k}{\text{)}}\!\!\!\!\cdot \frac{{S}_{{\rm{a}}}^{{\rm{T}}}\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\!}{{S}_{{\rm{a}}n}\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\!}{\text{,}} $
(7) This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
传统的频域法存在两个明显的问题:其一,在迭代过程中,存在迭代次数增加却无法提高收敛精度的频率控制点,这些点被称为顽固点,这些顽固点对应的傅里叶频率分量可能对于该频率反应谱值的收敛并非正贡献,若此时继续按照式(7)进行迭代,则无法使得顽固点收敛,甚至会产生发散的效果;其二,该方法对于相位谱未作任何约束,然而随机反应谱的选取对最终的拟合程度影响很大(胡聿贤,何训,1986;瞿希梅,吴知丰,1995)。基于以上问题,本文提出改进的综合方法,基于传统频域法进行修正,考虑迭代过程中频率分量是否正相关,同时考虑修改随机相位谱,以期达到更好的收敛效果。
2. 考虑迭代相关的反应谱拟合
This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
$ a\!\!\!\!{\text{(}}{\omega }_{k}{\text{,}}\!\!\!\!\!t{\text{)}}\!\!\!\!\cdot {a}_{{\omega }_{k}}\!\!\!\!{\text{(}}{\omega }_{k}{\text{,}}\!\!\!\!t{\text{)}}\!\!\!\! {\text{<}} 0{\text{,}} $
(8) This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
$ {S}_{{\rm{a}}n}\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\!{\text{>}}{S}_{{\rm{a}}}^{{\rm{T}}}\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\!{\text{,}} $
(9) $ \begin{aligned} {\ddot x_{{\rm{a}}\!\!\!\!{\text{(}}{n {\text{+}} 1} {\text{)}}\!\!\!\!}}\!\!\!\!{\text{(}}t {\text{)}}\!\!\!\! {\text{=}}& \sum\limits_{k {\text{=}} 1}^N {A}_{n {\text{+}}1} \!\!\!\!{\text{(}}\omega_k {\text{)}}\!\!\!\!{a_{{\omega _k}}}\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}\!\!\!\!t} {\text{)}}\!\!\!\! \cdot I\!\!\!\!{\text{(}}t {\text{)}}\!\!\!\! {\text{=}} \sum\limits_{k {\text{=}} 1}^N A_n\!\!\!\!\!\!\!\! &(\omega )\frac{{S_{\rm{a}}^{\rm{T}}\!\!\!\!{\text{(}}{{\omega _k}} {\text{)}}\!\!\!\!}}{{{S_{{\rm{a}}n}}\!\!\!\!{\text{(}}{{\omega _k}} {\text{)}}\!\!\!\!}}{a_{{\omega _k}}}\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}\!\!\!\!t} {\text{)}}\!\!\!\! \cdot I\!\!\!\!{\text{(}}t {\text{)}}\!\!\!\!{\text{,}} \end{aligned}$
(10) This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
${S_{{\rm{a}}\!\!\!\!{\text{(}}{n {\text{+}} 1} {\text{)}}\!\!\!\!}}\!\!\!\!{\text{(}}{{\omega _k}} {\text{)}}\!\!\!\! {\text{=}} {\omega _k}{\left| {\int _0^T {{\ddot x}_{{\rm{a}}\!\!\!\!{\text{(}}{n {\text{+}} 1} {\text{)}}\!\!\!\!}}\!\!\!\!{\text{(}}\tau {\text{)}}\!\!\!\! \cdot {\rm{exp}}\left[{ {\text{-}} \xi {\omega _k}\!\!\!\!{\text{(}}{T {\text{-}} \tau } {\text{)}}\!\!\!\!} \right] \sin {\omega _k}\!\!\!\!{\text{(}}{T {\text{-}} \tau } {\text{)}}\!\!\!\!{\rm d}\tau } \right|_{\rm max}}$
(11) $ {S}_{{\rm{a}}(n {\text{+}}1)}\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\!{ {\text{>}}S}_{{\rm{a}}n}\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\! {\text{>}}{S}_{{\rm{a}}}^{{\rm{T}}}\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\! $
(12) This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
$ {A}_{n{\text{+}}1}\!\!\!\!{\text{(}}\omega {\text{)}}\!\!\!\!{\text{=}}{A}_{n}\!\!\!\!{\text{(}}\omega_k {\text{)}}\!\!\!\! \cdot {\left({\frac{{S}_{{\rm{a}}}^{{\rm{T}}}\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\!}{{S}_{{\rm{a}}n}\!\!\!\!{\text{(}}{\omega }_{k}{\text{)}}\!\!\!\!}}\right)}^{c}{\text{,}} $
(13) $ c {\text{=}} \left\{ {\begin{array}{*{20}{l}} 1&\quad{a\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}\!\!\!t} {\text{)}}\!\!\!\! \cdot {a_{{\omega _k}}}\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}\!\!\!t} {\text{)}}\!\!\!\! {\text{>}} 0}{\text{,}}\\ { {\text{-}} 1}&\quad{a\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}\!\!\!t} {\text{)}}\!\!\!\! \cdot {a_{{\omega _k}}}\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}\!\!\!t} {\text{)}}\!\!\!\! {\text{<}} 0}{\text{,}} \end{array}} \right. $
(14) 式中,c代表迭代过程中的修正系数。
3. 考虑相位谱的反应谱拟合
某频率ωk在反应谱拟合过程中为顽固点,则存在两种情况:① 合成波对应的谱加速度大于设计反应谱加速度,谱最大加速度发生的时间为t,且存在该频率对应的傅里叶分量所产生的加速度分量在该时间与谱最大加速度同向;② 合成波对应的谱值小于设计反应谱值,谱最大加速度发生的时间为t,且存在该频率对应的傅里叶分量所产生的加速度分量在该时间与谱最大加速度反向。这两种情况由式(15)描述,在此种情况下,传统的迭代方法已经无法有效地使顽固点收敛,因此考虑对相位谱进行修正,过程如下:
$\left\{ { \begin{array}{*{20}{l}} \!\!\!{{S_{{\rm{a}}n}}\!\!\!\!{\text{(}}{{\omega _k}} {\text{)}}\!\!\!\! {\text{>}} S_{\rm{a}}^{\rm{T}}\!\!\!\!{\text{(}}{{\omega _k}} {\text{)}}\!\!\!\!}\\ \!\!\!{a\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}\!\!\!t} {\text{)}}\!\!\!\! \cdot {a_{{\omega _k}}}\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}\!\!\!t} {\text{)}}\!\!\!\! {\text{>}} 0} \end{array}\;\;{\text{或}}\;\;} \right.\left\{ {\begin{array}{*{20}{l}} \!\!\!{{S_{{\rm{a}}n}}\!\!\!\!{\text{(}}{{\omega _k}} {\text{)}}\!\!\!\! {\text{<}} S_{\rm{a}}^{\rm{T}}\!\!\!\!{\text{(}}{{\omega _k}} {\text{)}}\!\!\!\!}\\ \!\!\!{a\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}\!\!\!t} {\text{)}}\!\!\!\! \cdot {a_{{\omega _k}}}\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}\!\!\!t} {\text{)}}\!\!\!\! {\text{<}} 0} \end{array}} \right. $
(15) $ {\varphi '_k} {\text{=}} {\varphi _k} {\text{+}} {\rm{\pi }} $
(16) This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
$ x'\!\!\!\!{\text{(}}t {\text{)}}\!\!\!\! {\text{=}} \sin \!\!\!\!{\text{(}}{{\omega _k}t {\text{+}} {\varphi _k} {\text{+}} {\rm{\pi }}} {\text{)}}\!\!\!\! {\text{=}} {\text{-}} \sin \!\!\!\!{\text{(}}{{\omega _k}t {\text{+}} {\varphi _k}} {\text{)}}\!\!\!\! {\text{=}} {\text{-}} x\!\!\!\!{\text{(}}t {\text{)}}\!\!\!\!{\text{,}} $
(17) $\begin{aligned} a'\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}t} {\text{)}}\!\!\!\! {\text{=}}& {\rm{F^{-1}}}\left\{ {{H\!\!\!\!{\text{(}}\omega {\text{)}}\!\!\!\! \cdot {\rm{F}}\left[ {{x'\!\!\!\!{\text{(}}t {\text{)}}} } \!\!\!\right]} } \right\} {\text{=}} {\text{-}} {\rm{F^{-1}}}\left\{ {H {\!\!\!\!\text{(}}\omega {\text{)}}\!\!\!\!} \right.\left. \!\!\!\! \cdot{{\rm{F}}\left[ {x({t})} \right]} \right\} {\text{=}} {\text{-}} a\!\!\!\!{\text{(}}{{\omega _k}{\text{,}}\!\!\!\!t} {\text{)}}\!\!\!\!{\text{,}} \end{aligned}$
(18) $ H\!\!\!\!{\text{(}}\omega {\text{)}}\!\!\!\! {\text{=}}\frac{{ {\omega _k^2 {\text{+}} 2{\rm{i}}\xi {\omega _k}\omega } }}{{{\omega _k^2 {\text{-}} {\omega ^2} {\text{+}} 2{\rm{i}}\xi {\omega _k}\omega } }}{\text{,}} $
(19) This page contains the following errors:
error on line 1 at column 1: Start tag expected, '<' not foundBelow is a rendering of the page up to the first error.
4. 反应谱拟合案例
两种改进反应谱拟合过程的方法是考虑迭代相关的反应谱拟合以及考虑相位谱的反应谱拟合。本文以 《公路桥梁抗震设计规范》 (中华人民共和国交通运输部,2020)中的设计谱及美国核管会标准审查大纲(U.S. NRC,2014)中的核电厂设备的抗震需求谱分别作为目标谱,对比经改进之后的拟合方法与传统方法所生成的模拟结果。
考虑到相位谱的反应谱拟合方法对相位谱的修正较大,修正之后会显著增加迭代计算的计算量、运算时间,所以需严格约束此方法的使用范围和修正的迭代次数。具体改进方案如下:首先使用考虑迭代相关的反应谱拟合方法迭代10次,再使用考虑相位谱的反应谱拟合迭代1次,最后使用考虑迭代相关的反应谱拟合方法迭代9次,总共迭代20次,以此与使用传统拟合方法迭代20次的结果进行对比。
图1为使用3组随机相位谱,针对某公路桥梁抗震设计谱(中华人民共和国交通运输部,2020),通过传统方法和改进方法分别模拟出的6条人工地震波反应谱对比图,图2为传统方法与改进方法在高频以及低频部分的局部对比图,图(a),(b)和(c)分别对应于特定的一组随机相位谱。图3为图1a和1b中下行拟合结果所对应的人工地震波波形。表1列出了6条人工波反应谱与目标谱之间81个控制点的平均误差对比。从图1和表1可以看到,改进方法所生成的人工地震波反应谱与传统方法相比拟合精度有显著提高,尤其在高频段和低频段的顽固点数量大幅减少,误差最少降低50%。
表 1 改进方法和传统方法模拟人工地震反应谱的误差Table 1. Errors of response spectra of artificial ground motions generated by conventional and improved methods相位谱编号 反应谱平均误差 传统方法 改进方法 第一组 4.81% 1.40% 第二组 4.44% 1.37% 第三组 3.25% 1.60% 图4为使用三组随机相位谱分别通过传统方法和改进方法拟合而得的人工地震波反应谱对比图,其中各列子图对应一组随机相位谱,后两列为低频及高频部分的细部图。可以看到,无论是传统方法还是改进方法对于核电厂设计需求谱的拟合在频率中间段0.4—20 Hz的精度较高,但在高频及低频段均难以有效地拟合目标谱,部分原因是自然频率较高时单自由度体会随着地震波作刚体运动,地震波的加速度峰值即为高频段的谱加速度值,因此难以有效拟合。根据图4b和4c中的细部图可以发现在传统方法与改进方法都难以有效拟合的情况下,改进方法的拟合结果仍然较传统方法更接近目标谱的取值。
5. 结论
根据反应谱拟合人工地震波是结构抗震领域一个很重要的课题。然而,传统的频域法拟合人工地震波存在诸多问题,包括迭代效率低、顽固点多等。针对这些问题,本文通过优化频域法迭代过程中相关性的处理以及考虑相位谱的影响,提出综合改进的方法,通过提升拟合过程中迭代过程的工作效率进一步提高人工地震波对设计反应谱的拟合精度。算例结果表明,该方法的拟合精度较高,较传统方法有明显改进。
调整综合方法中两种改进方法的迭代次数、比例,形成更优化的综合方法,以进一步地提升迭代效率将是之后的研究重点。
-
图 1 研究区域及台站概况
(a) 区域构造背景、台站分布、历史强震及2008—2016年ML≥2.0地震分布;(b) 韩城台、龙门水文站、韩城断裂NE段和黄河的地理位置;(c) 韩城台及韩城断裂剖面图;(d) NS和EW分量金属水平摆;(e) 韩城台及周边地区与黄河之间地下水动力示意图
Figure 1. Map view of the investigation region and stations containing regional tectonic setting,earthquake events,hydrology and station locations
(a) Regional tectonic setting,the distribution of ML≥2.0 events during the period from 2008 to 2016 and significant historical earthquakes;(b) Distribution of the Longmen hydrological station,Hancheng station,NE segment of Hancheng fault and Yellow River;(c) Picture showing the Hancheng station and Hancheng fault plane;(d) Picture of NS and EW components of the metallic horizontal pendulums;(e) Conceptual cartoon illustrating the groundwater hydrodynamics between Hancheng station and Yellow River
图 5 黄河水位(a)、S34井水位(b)及运城气象站(c,d)观测的降雨变化
Figure 5. Hydrology and rainfall information of Hancheng station and its adjacent regions
(a) The water level of Yellow River recorded at Longmen hydrological station since 2007;(b) Changes in groundwater level in S34 well;(c) Time series of cumulative annual and daily precipitation observed at Yuncheng meteorological station;(d) Cumulative daily and detrended time series from 2001 to 2017
图 7 巨幅地倾斜异常前后研究区内85次2.0≤ML≤4.8地震的震源机制解及应力场反演结果
(a) 2008年10月10日至2010年2月26日研究区内28次地震的震源机制解;(b) 2010年3月14日至2015年9月15日研究区内57次地震的震源机制解;(c) 2008年10月10日至2010年2月26日研究区内应力张量;(d) 2010年3月14日至2015年9月15日研究区内应力张量
Figure 7. Focal mechanism solutions for the 85 earthquakes with 2.0≤ML≤4.8 and stress field inversion in the studied area before and after the remarkable tilt anomalies
(a) Focal mechanism solutions for the 28 earthquakes from Octorber 10,2018 to February 26,2010;(b) Focal mechanism solutions for the 57 earthquakes from March 14,2010 to September 15,2015;(c) The principal stress axes for the period from October 10,2008 to February 26,2010;(d) The principal stress axes for the period from March 14,2010 to September 15,2015
表 1 韩城台概况
Table 1 General information of Hancheng station
台基
岩性海拔
/m观测室情况 金属水平摆仪器参数 仪器支墩
材质及尺寸覆盖层
厚度/m室内气温
年变幅/℃室内气温
日变幅/℃相对
湿度仪器
类型记录
方式折合摆长
/mm使用周期
/s奥陶系
灰岩460 0 17—18 ≤0.5 90% JB 光记录 NS分量:25.2
EW分量:25.418—19 混凝土,
高0.7 m -
薄万举. 2010. 形变异常与干扰关系的再认识[J]. 大地测量与地球动力学,30(1):5–8. Bo W J. 2010. Study on relation between crustal deformation anomaly and disturbances[J]. Journal of Geodesy and Geodyna-mics,30(1):5–8 (in Chinese).
高伯贤,高雪. 2011. 韩城矿区南部奥陶系灰岩岩溶水特征[J]. 陕西煤炭,30(1):43–45. Gao B X,Gao X. 2011. Characteristics of Ordovician limestone karst water in southern Hancheng mining area[J]. Shaanxi Coal,30(1):43–45 (in Chinese).
郭平战. 2015. 韩城矿区岩溶形成机理及其水文地质特征[J]. 地下水,37(5):54–57. Guo P Z. 2015. Karst formation mechanism of karst in Hancheng mining area and its hydrogeological characteristics[J]. Ground Water,37(5):54–57 (in Chinese).
何毅. 2012. 近60年来渭河流域气候变化研究[D]. 杨凌: 西北农林科技大学: 16–37. He Y. 2012. Climate Change of Wei River Basin in Last 60 Years[D]. Yangling: Northwest A&F University: 16–37 (in Chinese).
黄辅琼,陈颙,白长清,张晶,晏锐,杨明波,兰从欣,张晓东,江在森. 2005. 八宝山断层的变形行为与降雨及地下水的关系[J]. 地震学报,27(6):637–646. Huang F Q,Chen Y,Bai C Q,Zhang J,Yan R,Yang M B,Lan C X,Zhang X D,Jiang Z S. 2005. The correlation of deformation behavior with precipitation and groundwater of the Babaoshan fault in Beijing[J]. Acta Seisomogical Sinica,27(6):637–646 (in Chinese).
扈桂让,李自红,闫小兵,赵晋泉,曾金艳,郭瑾. 2017. 韩城断裂晚第四纪活动性研究[J]. 地震地质,39(1):206–217. Hu G R,Li Z H,Yan X B,Zhao J Q,Zeng J Y,Guo J. 2017. The study of Late Quaternary activity of Hancheng fault[J]. Seismology and Geology,39(1):206–217 (in Chinese).
陆一锋,徐鸣洁,王良书,米宁,李华,于大勇. 2012. 鄂尔多斯东南缘地区的地壳结构[J]. 科学通报,57(1):59–64. Lu Y F,Xu M J,Wang L S,Mi N,Li H,Yu D Y. 2011. Crustal structure of the southeastern margin of the Ordos block[J]. Chinese Science Bulletin,56(35):3854–3859. doi: 10.1007/s11434-011-4847-7
牛安福,顾国华,曹景鹏,张凌空,闫伟,赵静,吉平. 2013. 芦山MS7.0地震前远、近场形变时空演化特征研究[J]. 地震学报,35(5):670–680. Niu A F,Gu G H,Cao J P,Zhang L K,Yan W,Zhao J,Ji P. 2013. On the preseismic deformation changes prior to the Lushan MS7.0 earthquake[J]. Acta Seismologica Sinica,35(5):670–680 (in Chinese).
水利部黄河水利委员会. 2017. 水情信息[EB/OL]. [2018–01–21]. http://61.163.88.227:8006/hwsq.aspx. Yellow River Conservancy Commission of the Ministry of Water Resources. 2017. The information of water[EB/OL]. [2018–01–21]. http://61.163.88.227:8006/hwsq.aspx (in Chinese).
吴富春,张鸿福,景北科,段锋,张义民. 1999. 陕西几例特殊的无震异常及其成因分析[J]. 西北地震学报,21(3):268–273. Wu F C,Zhang H F,Jing B K,Duan F,Zhang Y M. 1999. Study on some special aseismic precursory anomalies observed from Shaanxi seismic network and their causes[J]. Northwestern Seismological Journal,21(3):268–273 (in Chinese).
田中豊. 1972. 地殼変動連続観測(長期変動と地震前駆変動)[C]//地震予知研究シンポジウム. 东京: 东京大学出版社: 35–44. Tanaka Y. 1972. Long-term crustal deformation and precursory variation in seismicity[C]//Proceedings of the Earthquake Prediction Research Symposium 1972. Tokyo: University of Tokyo Press: 35–44 (in Japanese).
里嘉千茂. 1989. 伝播性歪に関する数値実験[J]. 測地学会誌,35(1):27–36. Sato K. 1989. Numerical experiments on strain migration[J]. Journal of the Geodetic Society of Japan,35(1):27–36 (in Japanese).
内藤宏人,吉川澄夫. 1999. 地殻変動解析支援プログラムMICAP-Gの開発[J]. 地震,52(1):101–103. Naito H,Yoshikawa S. 1999. A program to assist crustal deformation analysis[J]. Journal of the Geodetic Society of Japan,52(1):101–103 (in Japanese).
竹本修三, 和田安男, 伊藤潔, 福田洋一, 森井亙, 百瀬秀夫, 中村光邦. 2004. 地殻ひずみの観測に及ぼす局所的日照変化の影響—花山と立山観測室のデータ比較[R].京都大学防災研究所年報, 47(B): 725–734. Takemoto S, Wada Y, Ito K, Fukuda Y, Morii W, Momose H, Nakamura M. 2004. Effect of local sunshine changes upon crustal strain observations: Comparison of strain data obtained at Kwasan and Tateyama stations[R]. Disaster Prevention Research Institute Annuals, Kyoto University, 47(B): 725–734 (in Japanese).
Agnew D C. 1986. Strainmeters and tiltmeters[J]. Rev Geophys,24(3):579–624. doi: 10.1029/RG024i003p00579
Bilham R G,Beavan R J. 1979. Strains and tilts on crustal blocks[J]. Tectonophysics,52(1/2/3/4):121–138. doi: 10.1016/0040-1951(79)90216-6
Braitenberg C,Nagy I. 2014. Illustrating the superposition of signals recorded by the Grotta Gigante pendulums with musical analogues[J]. Acta Carsol,43(1):139–147.
Brimich L,Bednárik M,Bezák V,Kohút I,Bán D,Eper-Pápai I,Mentes G. 2016. Extensometric observation of Earth tides and local tectonic processes at the Vyhne station,Slovakia[J]. Contrib Geophys Geod,46(2):75–90. doi: 10.1515/congeo-2016-0006
Bykov V G,Trofimenko S V. 2016. Slow strain waves in blocky geological media from GPS and seismological observations on the Amurian plate[J]. Nonlin Process Geophys,23(6):467–475. doi: 10.5194/npg-23-467-2016
Caniven Y,Dominguez S,Soliva R,Peyret M,Cattin R,Maerten F. 2017. Relationships between along-fault heterogeneous normal stress and fault slip patterns during the seismic cycle:Insights from a strike-slip fault laboratory model[J]. Earth Planet Sci Lett,480:147–157. doi: 10.1016/j.jpgl.2017.10.009
Cicerone R D,Ebel J E,Britton J. 2009. A systematic compilation of earthquake precursors[J]. Tectonophysics,476(3/4):371–396.
Detournay E, Cheng A H D. 1993. Fundamental of Poroelasticity in Comprehensive Rock Engineering: Principles, Practice & Projects, Vol.2[M]. Oxford: Pergamon Press: 127–128.
Dragoni M,Bonafede M,Boschi E. 1984. On the interpretation of slow ground deformation precursory to the 1976 Friuli earthquake[J]. Pure Appl Geophys,122(6):781–792.
Eper-Pápai I,Mentes G,Kis M,Koppán A. 2014. Comparison of two extensometric stations in Hungary[J]. J Geodyn,80:3–11. doi: 10.1016/j.jog.2014.02.007
Evans K,Wyatt F. 1984. Water table effects on the measurement of earth strain[J]. Tectonophysics,108(3/4):323–337.
Fréchet J,Rivera L. 2012. Horizontal pendulum development and the legacy of Ernst von Rebeur-Paschwitz[J]. J Seismol,16(2):315–343. doi: 10.1007/s10950-011-9272-5
Fukuyama E. 2015. Dynamic faulting on a conjugate fault system detected by near-fault tilt measurements[J]. Earth Planets Space,67:38. doi: 10.1186/s40623-015-0207-1
Gershenzon N I,Bykov V G,Bambakidis G. 2009. Strain waves,earthquakes,slow earthquakes,and afterslip in the framework of the Frenkel-Kontorova model[J]. Phys Rev E,79(5):056601. doi: 10.1103/PhysRevE.79.056601
Goulty N R. 1976. Strainmeters and tiltmeters in geophysics[J]. Tectonophysics,34(3):245–256.
Hao M,Wang Q L,Cui D X,Liu L W,Zhou L. 2016. Present-day crustal vertical motion around the Ordos block constrained by precise leveling and GPS data[J]. Surv Geophys,37(5):923–936. doi: 10.1007/s10712-016-9375-1
Harada M,Furuzawa T,Teraishi M,Ohya F. 2003. Temporal and spatial correlations of the strain field in tectonic active region,southern Kyusyu,Japan[J]. J Geodyn,35:471–481. doi: 10.1016/S0264-3707(03)00008-5
Hardebeck J L,Shearer P M. 2002. A new method for determining first-motion focal mechanisms[J]. Bull Seismol Soc Am,92(6):2264–2276. doi: 10.1785/0120010200
Harrison J C,Herbst K. 1977. Thermoelastic strains and tilts revised[J]. Geophys Res Lett,4(11):535–537. doi: 10.1029/GL004i011p00535
Hisz D B,Murdoch L C,Germanovich L N. 2013. A portable borehole extensometer and tiltmeter for characterizing aquifers[J]. Water Resour Res,49(12):7900–7910. doi: 10.1002/wrcr.20500
Huang N E,Shen Z,Long S R,Wu M C,Shih H H,Zheng Q,Yen N C,Tung C C,Liu H H. 1998. The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis[J]. Proc Roy Soc A Math Phys Eng Sci,454(1971):903–995. doi: 10.1098/rspa.1998.0193
Ishii H,Sato T,Takagi A. 1980. Characteristics of strain migration in the northeastern Japan Arc (II):Amplitude characteris-tics[J]. J Geod Soc Japan,26(1):17–25.
Jahr T,Jentzsch G,Gebauer A,Lau T. 2008. Deformation,seismicity,and fluids:Results of the 2004/2005 water injection experiment at the KTB/Germany[J]. J Geophys Res,113(B11):B11410. doi: 10.1029/2008JB005610
Kartvelishvili K Z. 2010. Investigation of deformational processes in Tbilisi underground earth-tidal laboratory[J]. J Georgian Geophys Soc,Phys Atmos,Ocean and Space Plasma,14(B):197–201.
Kawai K,Sekine S,Fuji N R,Geller R J. 2009. Waveform inversion for D″ structure beneath northern Asia using Hi-net tiltmeter data[J]. Geophys Res Lett,36(20):L20314. doi: 10.1029/2009GL039651
Kimura T,Obara K,Kimura H,Hirose H. 2011. Automated detection of slow slip events within the Nankai subduction zone[J]. Geophys Res Lett,38(1):L01311. doi: 10.1029/2010GL045899
Linde A T,Gladwin M T,Johnston M J S,Gwyther R L,Bilham R G. 1996. A slow earthquake sequence on the San Andreas fault[J]. Nature,383(6595):65–68. doi: 10.1038/383065a0
Lindsey E O,FialkoY,Bock Y,Sandwell D T,Bilham R. 2014. Localized and distributed creep along the southern San Andreas fault[J]. J Geophys Res,119(10):7909–7922. doi: 10.1002/2014JB011275
Martínez-Garzón P,Kwiatek G,Ickrath M,Bohnhoff M. 2013. MSATSI:A MATLAB package for stress inversion combining solid classic methodology,a new simplified user-handling and a visualization tool[J]. Seismol Res Lett,85(4):896–904.
Mentes G. 2008. Observation of recent tectonic movements by extensometers in the Pannonian Basin[J]. J Geodyn,45(4/5):169–177.
Mentes G. 2017. The role of recent tectonics and hydrological processes in the evolution of recurring landslides on the Danube’s high bank in Dunaföldvár,Hungary[J]. J Geodyn,290:200–210.
Michelson A A. 1914. Preliminary results of measurements of the rigidity of the earth[J]. Astrophys J,39:105–138. doi: 10.1086/142058
NOAA. 2017. Climate data online[EB/OL]. [2017−10−12]. https://www.ncdc.noaa.gov/cdo-web/.
Okada Y. 1985. Surface deformation due to shear and tensile faults in a half-space[J]. Bull Seismol Soc Am,74(5):1135–1154.
Rikitake T. 1987. Earthquake precursors in Japan:Precursor time and detectability[J]. Tectonophysics,136(3/4):265–282.
Rikitake T. 1988. Earthquake prediction:An empirical approach[J]. Tectonophysics,148(3/4):195–210.
Schuite J,Longuevergne L,Bour O,Burbey T J,Boudin F,Lavenant N,Davy P. 2017. Understanding the hydromechanical behavior of a fault zone from transient surface tilt and fluid pressure observations at hourly time scales[J]. Water Resour Res,53(12):10558–10582. doi: 10.1002/2017WR020588
Sgrigna V,D'ambrosio C,Yanovskaya T B. 2002. Numerical modeling of preseismic slow movements of crustal blocks caused by quasi-horizontal tectonic forces[J]. Phys Earth Planet Int,129(3/4):313–324.
Stein R S,Barka A A,Dieterich J H. 1997. Progressive failure on the North Anatolian fault since 1939 by earthquake stress trig-gering[J]. Geophys J Int,128(3):594–604. doi: 10.1111/gji.1997.128.issue-3
Takemoto S. 1991. Some problems on detection of earthquake precursors by means of continuous monitoring of crustal strains and tilts[J]. J Geophys Res,96(B6):10377–10390. doi: 10.1029/91JB00239
Timofeev V Y,Ardyukov D G,Boyko E V,Gribanova E I,Semibalamut V M,Timofeev A V,Yaroshevich A V. 2012. Strain and displacement rates during a large earthquake in the South Baikal region[J]. Russ Geol Geophys,53(8):798–816. doi: 10.1016/j.rgg.2012.06.007
Timofeev V Y,Masalsky O K,Ardyukov D G,Timofeev A V. 2015. Local deformation and rheological parameters by measurements in Talaya station gallery (Baikal region)[J]. Geodyn Tectonophys,6(2):241–253. doi: 10.5800/GT-2015-6-2-0179
Tsai V C. 2011. A model for seasonal changes in GPS positions and seismic wave speeds due to thermoelastic and hydrologic variations[J]. J Geophys Res,116(B4):B04404. doi: 10.1029/2010JB008156
Wang H F. 2000. Theory of Linear Poroelasticity[M]. Princeton: Princeton University Press: 265–266.
Yamazaki K. 2013. An attempt to correct strain data measured with vault-housed extensometers under variations in temperature[J]. Tectonophysics,599:89–96. doi: 10.1016/j.tecto.2013.04.001
Zadro M,Braitenberg C. 1999. Measurements and interpretations of tilt-strain gauges in seismically active areas[J]. Earth Sci Rev,47(3):151–187.
-
期刊类型引用(4)
1. 刘莉,郑海刚,李军辉,倪红玉,周冬瑞. 基于观测环境的洞体应变压性异常综合研究. 大地测量与地球动力学. 2023(09): 980-985 . 百度学术
2. 朱琳,窦玛丽,郑怡. 华阴定点形变台地倾斜观测曲线趋势转折分析. 地震地磁观测与研究. 2022(S1): 356-358 . 百度学术
3. 雷生学,刘建波,闫伟,宋田,李昊,李恩健,朱冰清,李颖楠. 岩体完整性对载荷干扰定量分析的影响——以天津小辛庄应变为例. 地震地质. 2021(06): 1600-1613 . 百度学术
4. 李宏伟,吕睿,陈永前. 山西昔阳地震台水平摆异常综合分析. 山西地震. 2020(02): 36-40 . 百度学术
其他类型引用(0)