The traditional combined gravity and magnetic analysis uses the linear regression of the first order vertical derivative of the gravity anomaly and the reduction to the pole(RTP) magnetic anomaly,and provides the quan...The traditional combined gravity and magnetic analysis uses the linear regression of the first order vertical derivative of the gravity anomaly and the reduction to the pole(RTP) magnetic anomaly,and provides the quantitative or semi-quantitative interpretation by calculating the correlation coefficient,slope,and intercept.In the calculation process,due to the remanent magnetization,the RTP anomaly still contains the effect of oblique magnetization,as a result,the homologous gravity and magnetic anomalies may display irrelevant results in the linear regression calculation.To solve this problem,we present a new combined analysis using normalized source strength(NSS).Based on the Poisson's relation,the gravity field can be transformed into the pseudomagnetic field of the direction of geomagnetic field magnetization under the homologous condition.The NSS of the pseudomagnetic field and that of the original magnetic field are calculated,which are insensitive to the remanence,and then the linear regression analysis is carried out.The approach is tested using synthetic model under complex magnetization,the results show that it can still identify the gravity and magnetic anomalies from same source under strong remanence,and can establish the Poisson's ratio.Finally,this approach is applied in Wudalianchi in China.The results demonstrated that this approach is feasible and can provide the reference for further data processing and interpretation.展开更多
CHAMP high-quality vector magnetometer observations collected from July 2000 to September 2010 have been used to map the residual vector magnetic anomaly fields. This field is so called the lithospheric magnetic field...CHAMP high-quality vector magnetometer observations collected from July 2000 to September 2010 have been used to map the residual vector magnetic anomaly fields. This field is so called the lithospheric magnetic field which is the result of two contributions of the induced and the remanent magnetization. It is therefore essential to study the magnetic properties of the crustal rocks. Isolating this field from the other contributions, interpreting and even defining are however difficult and still debated. We investigate how to identify and separate the lithospheric vector magnetic field ΔX, ΔY and ΔZ from other contributions. For this purpose we use selected night magnetic data from which we remove a model field of degree 16 and external model field of degree 2 developed by spherical harmonics analysis. Concerning the induced lithospheric field which is assumed to be aligned with the internal dipole was also removed. To minimize the secular variation effects, we calculated internal models for each two months. The method developed here has been successfully applied to isolate lithospheric field produced by remanent magnetizations from CHAMP satellite data. The resolution and altitude measurements make it very hard to map short wavelength crustal magnetic anomalies. The large-scale strong magnetic anomalies detected using this technique are in agreement with previous global magnetic maps. These anomalies appear with an amplitude of about 10 nT at satellite altitude such as Bangui’s anomaly.展开更多
基金Supported by Project of National Natural Science Foundation of China(No.40930314)
文摘The traditional combined gravity and magnetic analysis uses the linear regression of the first order vertical derivative of the gravity anomaly and the reduction to the pole(RTP) magnetic anomaly,and provides the quantitative or semi-quantitative interpretation by calculating the correlation coefficient,slope,and intercept.In the calculation process,due to the remanent magnetization,the RTP anomaly still contains the effect of oblique magnetization,as a result,the homologous gravity and magnetic anomalies may display irrelevant results in the linear regression calculation.To solve this problem,we present a new combined analysis using normalized source strength(NSS).Based on the Poisson's relation,the gravity field can be transformed into the pseudomagnetic field of the direction of geomagnetic field magnetization under the homologous condition.The NSS of the pseudomagnetic field and that of the original magnetic field are calculated,which are insensitive to the remanence,and then the linear regression analysis is carried out.The approach is tested using synthetic model under complex magnetization,the results show that it can still identify the gravity and magnetic anomalies from same source under strong remanence,and can establish the Poisson's ratio.Finally,this approach is applied in Wudalianchi in China.The results demonstrated that this approach is feasible and can provide the reference for further data processing and interpretation.
文摘CHAMP high-quality vector magnetometer observations collected from July 2000 to September 2010 have been used to map the residual vector magnetic anomaly fields. This field is so called the lithospheric magnetic field which is the result of two contributions of the induced and the remanent magnetization. It is therefore essential to study the magnetic properties of the crustal rocks. Isolating this field from the other contributions, interpreting and even defining are however difficult and still debated. We investigate how to identify and separate the lithospheric vector magnetic field ΔX, ΔY and ΔZ from other contributions. For this purpose we use selected night magnetic data from which we remove a model field of degree 16 and external model field of degree 2 developed by spherical harmonics analysis. Concerning the induced lithospheric field which is assumed to be aligned with the internal dipole was also removed. To minimize the secular variation effects, we calculated internal models for each two months. The method developed here has been successfully applied to isolate lithospheric field produced by remanent magnetizations from CHAMP satellite data. The resolution and altitude measurements make it very hard to map short wavelength crustal magnetic anomalies. The large-scale strong magnetic anomalies detected using this technique are in agreement with previous global magnetic maps. These anomalies appear with an amplitude of about 10 nT at satellite altitude such as Bangui’s anomaly.
