Research of Geomagnetic Spatial‐Temporal Variations in China by NOC Method

Gu, Zheng; Chen, Bin; Gao, Jintian; Changjiang, Xin; Jiang, Yuan; Di, Chuan‐Zhi

doi:10.1002/cjg2.1431

Cited by 4 publications

(4 citation statements)

References 31 publications

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“…The above analysis shows that the more fine time change of the geomagnetic secular variation can be obtained by using the geomagnetic diurnal means than that by the geomagnetic annual means. And the geomagnetic diurnal means contain the abundant information of the external and internal fields, and can be used to analyze the geomagnetic obvious elements and analyze the different sources of the geomagnetic field; which is very significant [38] . However, the distribution of the used observatories is non-homogeneous, and there is no data of geomagnetic repeated survey for application; It induces unfavorable effect on analysis and research the geomagnetic secular variation.…”

Section: Discussionmentioning

confidence: 99%

Study of Geomagnetic Secular Variation in China

Chen¹,

Gu²,

Gao³

et al. 2010

Chinese J of Geophysics

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Using the data of the geomagnetic diurnal averages during 2000~2004 at 34 observatories in China, we calculated the mean annual change rates on the quiet days and all days, and the fitting annual change rates on the quiet days. The Taylor polynomial model and the spline model of the geomagnetic secular variation in China for epoch 2000.0~2005.0 were established based on the above annual change rates. The similarity and difference between the Taylor polynomial model, the spline model and the secular variation model of International Geomagnetic Reference Field (IGRF‐SV) were analyzed and discussed. The results show that the shape and the value of the Taylor polynomial model and the spline model for the geomagnetic secular variation in China are quite consistent, and their long‐term trends are also consistent with IGRF‐SV. However, the geomagnetic secular variation in China has some regional characteristics.

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Section: Discussionmentioning

confidence: 99%

Study of Geomagnetic Secular Variation in China

Chen¹,

Gu²,

Gao³

et al. 2010

Chinese J of Geophysics

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“…Based on the 6-order NOC nonlinear model of secular variations for the geomagnetic basic field [46][47][48][49] in China from 1995 to 2020, we obtain the secular variations for each observation in every year and correct their variation values.…”

Section: Data Preprocessing Methodsmentioning

confidence: 99%

Assessing Earthquake Forecasting Performance Based on Annual Mobile Geomagnetic Observations in Southwest China

Ni,

Chen,

Wang

et al. 2023

Atmosphere

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There have been reports about anomalies in mobile geomagnetic data before earthquakes; however, whether it can be used as an indicator for identifying potential earthquake areas was not be explored. In this study, we propose two parameters for earthquake forecasting based on annual mobile geomagnetic observation data. The spatial horizontal and three components’ changes are calculated in each year and then used to forecast moderate–large earthquakes (M ≥ 5.0) in southwest China in the subsequent period. It is found that earthquakes are more likely to occur in low H- or F-value regions. We statistically assess their forecasting performance by using Molchan’s error diagram, and the results indicate that there is considerable precursory information in the spatial H and F values. It is concluded that mobile geomagnetic observations might be useful in middle-term earthquake forecasts in the study area. We discuss the physical mechanisms of H and F values to explain their reasonability. The methodology proposed in this study could be helpful in finding out the optimal solution for annual mobile geomagnetic measurements for middle-term earthquake forecasting.

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“…The reference data used in the reduction of the diurnal variations were the minute mean values of the nearest geomagnetic observatory to repeat stations [37]. The reference data used in the reduction of the secular variation were from a 6-order natural orthogonal component (NOC) model of the geomagnetic secular variation in China [38,39].…”

Section: Source and Processing Of The Geomagnetic Datamentioning

confidence: 99%

“…• N, 103-112 • E, with the amplitude up to 100 nT for F and Z. There is also a positive anomaly(35)(36)(37)(38)(39)(40)(41)(42) • N, 75-88 • E) near Tarim Basin, with the amplitude up to 150 nT for F and 200 nT for Z. There are three significant negative anomalies, the first one located in Qinling Mountains(30)(31)(32)(33)(34)(35) • N, 103-115 • E), the second one located in Tianshan Mountains (38-42 • N, 75-90 • E), and the last one located in the south of Tibet (27-30 • N, 78-100 • E).…”

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confidence: 98%

Chinese Geomagnetic Reference Field 2020 by the Revised Surface Spline Method

Chen

Jiang

et al. 2022

Applied Sciences

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We improved the surface spline method to make the centers of the base functions fixed. This improvement makes it meaningful to analyze the time series of coefficients. Based on the revised surface spline (RSS) method and 2382 geomagnetic data measured in mainland China, we built Chinese Geomagnetic Reference Field 2020 (CGRF2020) to describe the spatial distribution of the geomagnetic field in most of China and surrounding areas. The root mean square residual is 0.1318 degrees for D, 0.0857 degrees for I, 93.70 nT for F, 73.94 nT for X, 65.02 nT for Y, and 97.82 nT for Z. The values of F, X, Y, and Z are about 20 nT less than those by the SCH method and IGRF13. We also preliminarily analyzed the correlation between geomagnetic anomalies and geological structures.

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Research of Geomagnetic Spatial‐Temporal Variations in China by NOC Method

Cited by 4 publications

References 31 publications

Study of Geomagnetic Secular Variation in China

Study of Geomagnetic Secular Variation in China

Assessing Earthquake Forecasting Performance Based on Annual Mobile Geomagnetic Observations in Southwest China

Chinese Geomagnetic Reference Field 2020 by the Revised Surface Spline Method

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