Abstract
CHAMP and Swarm satellite magnetic data are combined to establish the lithospheric magnetic field over the Tibetan Plateau at satellite altitude by using zonal revised spherical cap harmonic analysis (R-SCHA). These data are integrated with geological structures data to analyze the relationship between magnetic anomaly signals and large-scale geological tectonic over the Tibetan Plateau and to explore the active tectonic region based on the angle of the magnetic anomaly. Results show that the model fitting error is small for a layer 250–500 km high, and the RMSE of the horizontal and radial geomagnetic components is better than 0.3 nT. The proposed model can accurately describe medium- to long-scale lithospheric magnetic anomalies. Analysis indicates that a negative magnetic anomaly in the Tibetan Plateau significantly differs with a positive magnetic anomaly in the surrounding area, and the boundary of the positive and negative regions is generally consistent with the geological tectonic boundary in the plateau region. Significant differences exist between the basement structures of the hinterland of the plateau and the surrounding area. The magnetic anomaly in the Central and Western Tibetan Plateau shows an east–west trend, which is identical to the direction of the geological structures. The magnetic anomaly in the eastern part is arc-shaped and extends along the northeast direction. Its direction is significantly different from the trend of the geological structures. The strongest negative anomaly is located in the Himalaya block, with a central strength of up to −9 nT at a height of 300 km. The presence of a strong negative anomaly implies that the Curie isotherm in this area is relatively shallow and deep geological tectonic activity may exist.
Highlights
The lithospheric magnetic field accounts for approximately 4% of the total energy of the earth’s magnetic field [1]
Zonal revised of spherical cap harmonic analysis(R-SCHA) was used to model the lithospheric magnetic field of the Tibetan Plateau at satellite altitude
Considering that the difference between the latitude and longitude over the Tibetan Plateau is large, a small cap partition modeling can be used in a particular truncation level to provide good spatial resolution while ensuring accuracy
Summary
The lithospheric magnetic field accounts for approximately 4% of the total energy of the earth’s magnetic field [1]. The medium/long-wavelength signal of the lithospheric magnetic field was extracted and used in studies on tectonic structures in the deep crust and the top of the upper mantle, as well as the depth of the Curie surface and heat flow anomaly [12,13,14,15]. Using CHAMP and Swarm satellite magnetic data, the current study utilizes Sq local time conditions, Dst/Kp geomagnetic index conditions, Hamming along-track high-pass filtering, and the hierarchical gridding method, and combines. The present paper adopts zonal revised spherical cap harmonic analysis to inverse the lithospheric magnetic field over the Tibetan Plateau and analyzes the relationship between magnetic anomalies and geological structures to explore the active region of geological structures
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