Accurate Correction Models for Tidal Gravity in Chinese Continent

Zhou, Jixue; Xu, Jun; Sun, Heping

doi:10.1002/cjg2.1379

Cited by 5 publications

(3 citation statements)

References 28 publications

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“…Among these tidal waves, M 2 has the largest amplitude for the loading vector of oceanic tides of 4.122 nm s , which is only about 0.6% of the observed amplitude for gravity tides. In the diurnal frequency band, the strongest effect of oceanic tide loads on gravity tides is that for K 1 , whose amplitude is only 1.667 nm s For the other tidal waves with lower amplitudes, the oceanic tide loading vectors were obtained by interpolating or extrapolating in the frequency domain [34]. The loading vector of the oceanic tide for wave M 4 was obtained using the co-tide maps provided by global oceanic tides model Fes2004.…”

Section: Loading Effects Of Oceanic Tides and Atmospherementioning

confidence: 99%

Characteristics of tidal gravity changes in Lhasa, Tibet, China

Chen

Zhou

et al. 2012

Chin. Sci. Bull.

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Tidal gravity changes arise from the response of the solid Earth to the tidal forces of the Sun, Moon and planets close to the Earth, and are a comprehensive reflection of the structure and distribution of physical properties of the Earth's interior. As a result, observations of tidal gravity changes are the basis of studies on other global and/or regional dynamic processes. The characteristics of tidal gravity changes in the region of the Tibetan Plateau were investigated through continuous gravity measurements recorded with a superconducting gravimeter (SG) installed in Lhasa over a year. Through contrast measurements with a spring gravimeter LaCoste-Romberg ET20 at the same site, the gravity observations in Lhasa were scaled to the international tidal gravity reference in Wuhan. Meanwhile, the scale factor of the SG was determined accurately as -777.358 ± 0.136 nm s −2 V −1 , which is about 2.2% less than the value provided by the manufacturer. The results indicate that the precision of the tidal gravity observations made with the SG in Lhasa was very high. The standard deviation was 0.459 nm s −2 , and the uncertainties of for the four main tidal waves (i.e. O 1 , K 1 , M 2 and S 2 ) were better than 0.006%. In addition, the observations of the diurnal gravity tides had an obvious pattern of nearly diurnal resonance. As a result, it is affirmed that the Lhasa station can provide a local tidal gravity reference for gravity measurements on the Tibetan Plateau and its surrounding regions. The loading effects of oceanic tides on tidal gravity observations in Lhasa are so weak that the resulting perturbations in the gravimetric factors are less than 0.6%. However, the loading effects of the local atmosphere on either the tidal or nontidal gravity observations are significant, although no seasonal variations were found. After removal of the atmospheric effects, the standard deviation of the SG observations in Lhasa decreased obviously from 2.009 to 0.459 nm s −2 . Having removed the loading effects of oceanic tides and local atmosphere, it was found that the tidal gravity observations made with the SG in Lhasa significantly differed by about 1% from those expected theoretically, which may be related to active tectonic movement and the extremely thick crust in the region of the Tibetan Plateau. A more-certain conclusion requires longer accumulation of SG data and further associated theoretical studies.

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Section: Loading Effects Of Oceanic Tides and Atmospherementioning

confidence: 99%

Characteristics of tidal gravity changes in Lhasa, Tibet, China

Chen

Zhou

et al. 2012

Chin. Sci. Bull.

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“…Chen et al., 2019; Wan et al., 2019). However, accompanying with the accumulation of more and more seismic data, some problems about the timing anomalies have been found recently, and relevant solutions have been proposed for Chinese OBS (Li et al., 2023; Wang et al., 2016; Zhang et al., 2018, 2019.). These timing errors in OBS data will be a limiting factor in other researches, such as the high‐precision earthquake locations and associated tomographic inversions for velocity structure.…”

Section: Introductionmentioning

confidence: 99%

Analysis of clock drift based on a three‐dimensional controlled‐source ocean bottom seismometer experiment

Zhang

Zhao

Yao

et al. 2023

Geophysical Prospecting

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Clock drift is common for the autonomous ocean bottom seismometer, and a technique of linear drift correction is usually used to fix this kind of timing error assuming that the internal clock has constant drift rate during deployment. However, non‐linear component of clock drift has also been found recently. In order to test the behaviours of the clock drift for 19 Chinese ocean bottom seismometers from a three‐dimensional controlled‐source seismic survey, we have analysed two types of differences in direct wave travel‐times, including one from all shots to the ocean bottom seismometer onboard and another one from the nearest two shots on different shooting lines to the ocean bottom seismometer on the seafloor. Comparison of the differences in direct wave travel‐times from seismic data with and without clock drift correction shows that linear drift correction can commendably eliminate them for most of the ocean bottom seismometers, but some large residuals remain for part of the ocean bottom seismometers. These residuals are inferred to be possibly related to the non‐linear component of clock drift caused by the temperature shock during deployment. The non‐linear clock drift usually varies from different ocean bottom seismometers and thus difficult to correct completely and resultantly will influence the timing accuracy somewhat. Hence, higher uncertainties are suggested to assign to the picked travel‐times for the ocean bottom seismometer with possibly larger non‐linear clock drift in the further tomographic modelling and the internal clock for this kind of ocean bottom seismometer should be recalibrated prior to the next experiment if which requires higher timing accuracy.

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“…Sibson used it to explain cyclic movements of such faults in Quebec area. Zhou et al [10] suggested movements of these faults at Longmenshan were related to highly geo-pressured fluids within them, which triggered the slipping movement of these faults and was a requirement which induced Wenchuan earthquake.…”

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confidence: 99%

Discussions on the Formation Mechanism of High-Angle Reverse Faults in Sanan Oil Field

Yang

Shou

Wang

et al. 2014

AMM

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Formation mechanism of high-angle reverse faults has always been one of the questions concerning structural geologists. The mechanics of high-angle reverse faults does not conform to the Mohr-Coulomb criterion or Anderson’s theory of faulting. Geologists tried to explain the formation mechanism of high-angle reverse faults by inversion structure theory, Maximum Effective Moment Criterion and fault-valve model and so on. It is hard to explain the mechanism of high-angle reverse faults in Sanan oilfield with these viewpoints. It is considered that the cause of formation of such high-angle reverse faults was that the dip direction of normal fault plane has been overturned by the intensive superposed folding and interlayer gliding. “Overturned fault dip” can be regarded as a new type of inversion structure and supplements the existing types of inversion structure.

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Accurate Correction Models for Tidal Gravity in Chinese Continent

Cited by 5 publications

References 28 publications

Characteristics of tidal gravity changes in Lhasa, Tibet, China

Characteristics of tidal gravity changes in Lhasa, Tibet, China

Analysis of clock drift based on a three‐dimensional controlled‐source ocean bottom seismometer experiment

Discussions on the Formation Mechanism of High-Angle Reverse Faults in Sanan Oil Field

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