【作者】 王庆良；

【导师】 陈运泰；

【作者基本信息】 中国地震局地球物理研究所 ， 固体地球物理学， 2003， 博士

【摘要】 地球自转速率(或日长)变化具有典型的十年尺度波动特征，该十年尺度波动主要是由深部核-幔间的角动量转换引起的。已提出了三种可能的核幔耦合机理即核幔地形耦合、电磁耦合、引力耦合，但至今没有一个被完全证实或排除。与日长十年波动变化类似，地壳形变、地球物理场也具有数年～数十年的波动变化特征，但其波动演化机理目前还不清楚。为探索地壳形变、地球物理场波动与地球自转速率变化之间可能的内在机理联系，本论文广泛收集整理了中国大陆近200处场地的断层形变监测资料、30余个台站的地倾斜观测资料、20余个台站的应力／应变观测资料、7个台站的重力变化观测资料、8个台站的地温观测资料，其观测时间跨度一般为10～30年。除台站观测资料外，本文还收集整理了河西-祁连山地区近30年的区域垂直形变监测资料以及首都圈地区近20年的流动重力监测资料。除中国大陆监测资料之外，笔者还利用Internct资源和e-mail通讯联系等方式，收集到了美国加州San Andreas断层的形变监测资料、意大利东北部Friuli地区的台站地倾斜、应变观测资料以及全球近200台站的地磁年均值观测资料。对比研究发现，地壳形变、地球物理场的波动变化有相当一部分是与地球自转速率变化十年尺度波动相关的，且这种十年尺度相关性具有全球准同步变化、原始形态相关、去线性相关、转折点相近、方向依赖性等多种特点。从变化量级上，日长十年尺度波动相关的断层形变幅度一般可达数毫米，San Andreas断层则可达数厘米，地倾斜变化幅度可达4～5弧度秒，地应力变化幅度可达数百kPa，应变波动幅度可达10-6量级，地表重力场变化幅度可达数十微伽(10-8m／s2) ，区域地壳垂直差异运动幅度可达数厘米(河西-祁连山地区)。理论上，地球自转速率变化离心力可以引起地表位移、倾斜、应变以及重力场的十年尺度波动，但其理论值普遍比实际观测到的十年尺度波动小4～5个数量级，因此，地球自转速率变化不是地壳形变-地球物理场-日长变化十年尺度相关性的主要原因。联合参考日长十年尺度波动研究结果和地磁长期变化研究结果，地壳形变-日长变化十年尺度相关性最可能的机理解释是：外核流速场扰动一方面通过核幔角动量转换引起地幔自转速率的波动变化(地幔-地壳的刚体运动行为)，另一方面又通过核幔边界力变化引起地壳形变的波动变化(地幔-地壳的弹性变形行为)，即日长十年尺度波动与地壳形变十年尺度变化均源于核幔耦合作用。地磁场的十年尺度波动变化是外核流速场变化的直接电磁感应反映；地表重力场十年尺度波动变化则联合受到核幔边界力引起的地壳密度变化、地球内部密度介面变化等因素的影响；浅层地温-日长变化十年尺度相关性的最可能机理解释为：核幔耦合引起了地壳浅层应力场的波动变化，地壳应力场波动变化又通过岩土介质的比热变化等机理引起浅层地温的变化。青海平安台特殊“固体潮型”地温日波-半日波现象，则与日月引潮力以及该台石英晶体温度传感器的压电效应密切相关。由于地球自转速率变化仅与地幔底部纬向剪切力矩变化有关，而地壳形变、地表重力场等的变化则既与地幔底部纬向拖曳力变化有关，也与地幔底部经向拖曳力、径向正压力变化有关，除此之外，地幔-地壳介质的结构不均匀性也对核幔边界力作用下的地壳变形特征起着十分重要的影响，因此，地壳形变-地球物理场-日长变化的十年尺度相关性现象表现得相当复杂。 地壳形变一地球物理场一日长变化十年尺度相关性的地球动力学意义主要表现在三方面:其一，它揭示了核慢藕合作用是地壳形变、地球物理场波动式演化的主要力源之一;其二，作为一种重要约束条件，它否定了核慢引力祸合机理对日长十年尺度波动的重要贡献;其三，根据地磁变化滞后日长变化4一6年的特征时间，可以反演确定出下地慢的电导值为10怡量级，该电导值意味着慢电磁藕合是日长十年尺度波动的主要激发机制之一。 地壳形变一地球物理场一日长变化十年尺度相关现象系统发现对地震预报工作的重要意义主要表现在:它揭示了核慢祸合作用是地震前兆监测资料背景性异常变化的主要调制机理之一，因此，利用天文观测取得的日长变化资料，有可能帮助提高前兆异常信息识别的可靠性。更多还原

【Abstract】 Decade fluctuation in length of day （lod） is one typical features of the Earth’s rotation variation, which is generally attributed to exchanges of angular momentum between the core and the mantle. Three possible core-mantle coupling mechanisms, topographic coupling, electromagnetic coupling and gravitational coupling, have been proposed, but no one was thoroughly, verified or ruled out. Similar to decade fluctuation of lod, crustal deformation and geophysical field also fluctuate on time scales of several years to decade years, the mechanisms are not well understood yetIn order to explore the possible correlation between fluctuations of lod and variations of crustal deformation as well as geophysical observations, we extensively collected observation data obtained at earthquake-precursor observatories （sites） in Chinese mainland, which including fault deformation monitoring data of nearly 200 fault sites, ground tilt observations of over 30 gauges, stress/strain observations of over 20 gauges, gravity change observations of 7 stations, shallow soil temperature observations of 8 stations, the time spans of the collected observation data are generally 10 to 30 years. Apart from the observation data of earthquake-precursor observatories, we also collected the repeated leveling data of Hexi-Qilian mountain area with time span of 30 years, and repeated gravity measurement data of Beijing area with time span of 20 years. By Internet resources and e-mail communication, we also obtained the deformation data of San Andreas Fault, California, as well as the tilt/strain observations of Friuli area, NE Italy. The annual values of geomagnetic filed at 200 observatories all over the world were also downloaded from the World Data Center.Time series comparisons demonstrate that, quite part of fluctuations in crustal deformation and geophysical observations are dynamically correlated to decade variation of lod. The decade correlation between lod and crustal deformation as well as geophysical observations usually appears as globally quasi-synchronous change, location-dependent and direction-dependent. The decade correlation not only exists in original observations, but also appears in the detrended observations in many cases.As observed, the lod-correlated variation of fault deformation and tilt observations can reach respectively several centimeters and 4 to 5 arc seconds at maximum, the maximum variation of strain, stress and gravity correlated to lod fluctuation, then, can reach 10^-6 order, several kPa and several decades Gal respectively, regional vertical deformation change correlated to lod can also reach the maximum of several centimeters （for example, the Hexi corridor-Qilian mountain area）.Theoretically, decade variation of the Earth’s rotation rate may induce decadal fluctuations of surface displacement, tilt, strain and gravity by centrifugal potential or force, the induced theoretical variations, however, are generally 4⁵ order less than the observed fluctuations, so rotational rate change of the earth is not the major mechanism for decadal correlation between crustal deformations, geophysical variations and length of day.Jointly referring to research results on decade variation of lod and secular variation of geomagnetic field, the most possible mechanism for decade correlation between crustal deformations and length of day is: flow disturbance of the outer core induces decadal fluctuation of the mantle’s rotational rate on one hand by angular momentum exchange （rigidity behavior of the mantle and the crust）, and causesdecadal fluctuations of crustal deformation on the other hand by core-mantle boundary （CMB） forces （elastic behavior of the mantle and the crust）, both decadal variations of lod and crustal deformations arise from core-mantle coupling process.Decadal variation of main geomagnetic filed directly arises from electromagnetic induction induced by flow disturbance of the outer core. Decade fluctuations of surface gravity observations are closely related to core-mantle coupling induced crus更多还原