The Large Ring Laser G for Continuous Earth Rotation Monitoring

Ring Laser gyroscopes exploit the Sagnac effect and measure rotations absolute. They do not require an external reference frame and therefore provide an independent method to monitor Earth rotation. Large-scale versions of these gyroscopes promise to eventually provide a similar high resolution for the measurement of the variations in the Earth rotation rate as the established methods based on VLBI and GNSS. This would open the door to a continuous monitoring of LOD (Length of Day) and polar motion, which is not yet available today. Another advantage is the access to the sub-daily frequency regime of Earth rotation. The ring laser “G” (Grossring), located at the Geodetic Observatory Wettzell (Germany) is the most advanced realization of such a large gyroscope. This paper outlines the current sensor design and properties.     

Aspects Of Ring Lasers As Local Earth Rotation Sensors

Ring laser rotation sensors are best known from inertial navigation, wherethey have many advantages over mechanical gyroscopes. They have recentlybeen greatly improved, and show potential as fully independent length-of-daysensors. We discuss some important aspects of current limitations in theirperformance. In particular we demonstrate a novel scheme for thestabilisation of a large ring laser against frequency pulling effectsinduced by backscatter.     

Tides and Earth Rotation

A short general explanation of tidal forces and tidal effects is given. The influences of Earth tides and ocean tides on the Earth's rotation vector are presented. Today, the theoretical models for periodic variations in the Earth's rotation and in polar motion can be compared with precise measurements done by modern space techniques. Secular changes of the Earth's rotation due to interactions within the Earth-Moon-system are also discussed.     

JCZ-1型地震仪观测的地球环型自由振荡

本文首次采用JCZ-1型地震仪观测资料研究地球环型自由振荡, 并在2011年日本9.0级地震、 2010年智利8.8级地震和2005年印尼8.6级地震后武汉地震台JCZ-1型地震仪观测到了其激发的环型自由振荡, 从中检测了基振型₀T₂~₀T₆₇和一次振型 ₁T₂~₁T₅₀等振型的本征周期, 与PREM的理论值比较, 误差比小于0.5%, 补充了PREM中未提到的几次振型的本征周期: ₀T₁₁、 ₀T₁₅、 ₀T₁₉、 ₁T₄、 ₁T₅、 ₁T₁₄, 并观测到了日本地震 ₀T₂、 ₀T₆、 ₀T₇和 ₀T₈振型的多峰值现象。 研究结果表明, JCZ-1型地震仪具有良好的观测超低频长周期地球自由振荡的能力。     

地球自转、地震成因与地震预报

通过对2008年5月12日四川汶川8级地震与地球自转的关系的分析,提出了一个新的地震成因观点,认为地震的主要成因之一在于地球自转速率的变化。地球岩石圈由大小不同、质量不同的块体组成。比如,大洋块体薄、质量轻,大陆块体厚、质量重。地球自转速率变化时,就会造成这些块体运动的差异性。这种差异运动可能使块体之间发生"追尾"撞击或摩察,从而引起地震。     

兰州地磁台GM3磁力仪基线值变化特征和处理方法探讨

根据兰州地磁台2002年GM3磁通门磁力仪观测基线值数据,分析了基线值的变化规律和影响因素,并把影响因素定量掺入到对基线的平滑过程中,将得到的结果与FHD-1仪观测数据的处理结果做比较,得出基线值主要受温度系数和漂移影响。在对基线值进行平滑时定量考虑温度系数对基线值的影响程度,是提高地磁最终观测结果精确度可行且有效的方法。     

Free Wobble of the Triaxial Earth: Theory and Comparisons with International Earth Rotation Service (IERS) Data

Earth’s free wobble is often referred to as the Euler wobble (for the rigid case) or the Chandler wobble for the real case. In this study, we investigate the theory of the free wobble of the triaxial Earth and demonstrate that: (1) the Euler period should actually be expressed by the complete elliptic integral of first kind, and (2) the trace of the free polar motion is elliptic, with the orientations of its semi-minor and major axes being approximately parallel to the Earth’s principal axes A and B, respectively. Numerical calculations show that, due to the triaxiality of the Earth, the spin rate ω ₃ fluctuates with the semi-Euler/Chandler period, although its amplitude (about 10⁻¹⁹ rad/s) is rather small and beyond the present measurement accuracy; the tilt of the instantaneous spin axis (or the amplitude of the free wobble), θ, has a fluctuation whose amplitude is around 0.34 milli-arcsecond (mas), which could be detected by present observations. Thus, we conclude that the Earth’s triaxial nature has little impact on ω ₃, but has an influence on the polar motion which should not be ignored. On the other hand, our study shows that there is a mechanism of frequency–amplitude modulation in the Chandler wobble which might be a candidate to explain the correlation between the amplitude and period of the Chandler wobble. We compare the theoretical polar parameters (m ₁, m ₂) with the observed values for the Chandler components obtained from the data EOP (IERS) C 04, and find that they coincide with each other quite well, especially for recent years. In addition, a polar wander towards 76.7°W, which is in agreement with previous results given by other scientists, is also obtained.     

Residual circulation in eastern Long Island Sound: Observed transverse-vertical structure and exchange transport

Residual currents in eastern Long Island Sound (LIS) are investigated using direct velocity measurements from an acoustic Doppler current profiler mounted on a ferry. Circulation at the site has major influence on exchange of water and water-borne materials between LIS and the coastal ocean. Ferry sampling enables sufficient averaging to isolate the residual motion from stronger tidal currents, and captures its spatial structure. Mean along-estuary currents based on about 2 years of sampling reveal a vigorous estuarine exchange circulation (peak 25–30 cm s⁻¹ at depth), with flow eastward out of the estuary in the upper water column of the southern half and inward westward movement strengthening with depth over the central and north section. Application of volume conservation implies there is a strong eastward current out of the estuary in the shallowest 7 m where no measurements were made, as expected for estuarine exchange flow. Water from the Connecticut River, entering LIS on the north shore nearby to the west, does not appear to exit the estuary directly eastward along the north shore unless this occurs wholly in the shallow layer not sampled. Transverse currents have complex structure with generally northward (southward) flow where shallow outward (deep inward) motion occurs. An idealized semi-analytic solution for transverse-vertical structure of along- and across-estuary flow has limited success accounting for observed currents, despite inclusion of bathymetric, frictional, and rotational influences; this suggests the importance in LIS of dynamics it omits, in particular stratification, or does not represent with sufficient realism, such as complex bathymetry. Estimated annual-mean exchange volume transport, based on the better-sampled deep inward component, is 22,700±5000 m³ s⁻¹. This is comparable to previous estimates from some salt budget and hydrographic analyses, and implies advection contributes substantially to the total salt transport, contrary to results of a recent box-model analysis of hydrographic measurements. At seasonal timescales, changes to the transverse-vertical velocity structure are modest, but amplitude variations cause exchange volume transport increases (decreases) to 30,000 m³ s⁻¹ (18,000 m³ s⁻¹) in the summer (winter) months; a power-law dependence of exchange on river flow, as seen in other estuaries, is not supported. Strengthened summer transport is associated with enhanced stratification, suggesting that mixing effects modulate the exchange. To the extent that advection by residual flow contributes to total exchange between LIS and coastal waters, the flushing of materials from LIS should occur substantially faster in summer than in winter.     

Sub-Daily Earth Rotation Parameters and the International GPS Service Orbit/Clock Solution Products

Tidally induced sub-daily Earth Rotation Parameters (ERP) variations, when not properly accounted for, can cause apparent orbit and ERP rate errors, which can significantly exceed the IGS solution errors. All International GPS Service (IGS) Analysis Centers currently apply the conventional sub-daily ERP model in their transformations from ITRF (International Terrestrial Reference Frame) to ICRF (International Celestial Reference Frame), both of which are used for IGS global analyses. However, some IGS Analysis Centers did not apply the sub-daily ERP model when transforming ICRF orbit solutions to ITRF, which is used for IGS orbit/clock products. This transformation inconsistency can cause significant orbit RMS differences that could exceed the 5-cm level. Independent ERP rate solutions are sensitive even to small errors in the sub-daily ERP model, and can be used to verify the sub-daily ERP model at, or below 0.1 mas/day precision level.The Precise Point Positioning (PPP) via precise station position solutions with the IGS orbit/clock combined products, provides an ideal interface to access the IGS realization of ITRF. PPP also yields precise station clock and tropospheric zenith delays (TZD) solutions, all at the sub-cm precision level. However, when using IGS orbit/clock products it is important that the same convention be used with respect to sub-daily ERP. Otherwise, the solutions of station navigation positions, station clocks and TZD's will be affected by significant errors that could exceed the 1-cm level.     

由泰安地震台形变资料看固体潮数字化观测运行

泰安地震台为全国形变一类观测台。现有除重力仪、井下竖直摆外的几乎所有形变固体潮数字化观测仪器。通过对山东泰安台固体潮形变观测的数字化与模拟资料的一致性、精度和格值的对比研究,以及对数字化资料连续性、稳定性的综合统计分析,对各套仪器的运行状况进行了评价和论证。认为数字化与模拟观测资料的固体潮形态、观测精度、方差及均值无显著性差异。在数字化倾斜仪中,水管倾斜仪的稳定性及精度较高,石英摆存在一定程度的漂移,垂直摆倾斜仪的漂移较大、资料内精度较低。伸缩仪资料也存在精度较低的情况;压容及体应变仪资料内精度较高,但压容仪漂移较大,仪器稳定性不及体应变仪。     

几次强震及震前震中附近地区中小地震与地球自转的关系

本文分析了1975年海城7.3级、 2008年汶川8.0级和2004年印尼苏门答腊9.0级地震与地球自转的关系, 给出了震前震中附近地区中小地震与地球自转之间较好的相关关系。 结果对深入认识地球自转与地震发生之间的关系具有裨益。     

地球自转速率变化与中国西部的大地震

分析讨论了地球自转速率的变化与中国地震活动强度大的西部地区1900年以来的大地震的关系，所考察的地区主要包括西藏、青海、甘肃南部及陕西的西部。结果表明，该地区M≥7．5的大地震发生的当年及前一年，地球自转速率往往处于相对加快的状态，这个特点在M≥8．0的特大地震的发生中表现得更为明显。结果还显示，当地球自转的季节性变化处于转折期时，该地区大地震的频次明显增加。研究的结果表明该地区的大地震的发生与地球自转变化具有较密切的相关性。     

长基线法和短基线法在LCR-G型重力仪格值因子标定中的应用

介绍了LCR-G型重力仪长、短基线标定格值因子的方法和过程,并对标定结果进行比较。统计了两台重力仪2008—2017年在灵山基线场标定的格值因子,分析了时序变化规律,总结了该种仪器长、短基线标定的优点、不足和适用范围。     

川滇地区地震活动与地球自转速率变化之间的关系

利用川滇地区1962—2016年间发生的MS≥6.0地震资料,在去除余震的情况下,分析了其发生与地球自转速率变化极值点之间的关系。得到以下结果:川滇地区MS≥6.0地震的发生与地球自转速率变化极值点具有显著关系,对于不同震级范围的地震,其与不同周期的地球自转速率变化有关。对于MS≥7.0的地震,有90%发生在地球自转速率季节性变化极值点前14天至后37天时间段内;对于6.0≤MS≤6.4的地震,有80%发生在地球自转速率短周期变化极值点前68小时至后30小时的时间段内;对于6.5≤MS≤6.9的地震,有87.5%发生在地球自转速率短周期变化极值点前36小时至后64小时的时间段内。地震发生在特定时间段的显著性检验结果表明,川滇地区MS≥6.0地震与地球自转速率变化极值点的关系都可以在α=0.05的显著性水平下通过显著性检验。这个结果表明,在地球自转速率发生转折的期间容易触发地震,对川滇地区地震发生时间预测具有参考意义。     

The Relationship between Multifractal and Entropy Properties of Seismic Noise in Kamchatka and Irregularity of the Earth’s Rotation

Izvestiya, Physics of the Solid Earth - Abstract—The connection between the properties of seismic noise continuously recorded by the network of 21 broadband seismic stations in...     

Long Term Time Variability of Cosmic Rays and Possible Relevance to the Development of Life on Earth

The well-known 11-year cycle in low cloud cover amount for Solar Cycle Number 22 and the trend with time for Solar Cycle Number 23 are interpreted as being due to similar changes, but of opposite phase, in the mean global surface temperature of the Earth. An analysis of cloud amounts in two higher altitude bands shows that they, and the surface temperature, are roughly in phase with each other. The suggested mechanism to explain this result is that a warming of the Earth’s surface causes low clouds to rise and to be reclassified in the next upper category. The energetics of the process are shown to be satisfactory for this to be the correct explanation.     

绝对重力测量在云南和北京观测到的重力时间变化

中国地震局地震研究所与德国汉诺威大学大地测量研究所于１９９０,１９９２和１９９５年共同在滇西地震预报实验场和昆明进行了３次绝对重力测量。此外,１９９０,１９９２年在北京,１９９０年在武汉也进行了绝对重力测量。通过对各次绝对测量的结果进行比较,并与其它重力仪获得的数据的对比估算了它们的可靠性,进而详细地讨论了各个测点的重力变化。