There is a method which makes regular subdivision of the source region into a set of juxtaposed cuboids and estimation of physical properties of the cuboids using an inversion of potential field to deduce the image of the geological sources. It is currently prevailing in geophysical interpretation, especially in 3‐D gravity and magnetic inversion. Nonlinear global methods, such as the Genetic Algorithms, gradually play a leading role in the inversion. This paper shows that there exists an excessive computation that has bottlenecked the effectiveness of nonlinear global methods including the Genetic Algorithms. Several special tricks are proposed to break the choke point of overwhelming computation, one of which is to separate the geometric trellis from formulas. The trellis is invariable during the whole process of inversion, and stored as a table, which would make the following reiterative forward computation as just a simple reading of the table and multiplying it with corresponding properties of the geometric cells. The required huge storage of geometric trellis has been tremendously reduced by a very skill of equivalent storing. The approaches revive the nonlinear methods in their applications to the inversion of gravity and magnetic anomalies for 3‐D physical properties.

This letter proposes an ultra-wideband and high-gain antipodal tapered slot antenna (ATSA) with gradient refractive index (GRIN) lens. The GRIN lens consisting six metamaterial lenses is placed in the maximum radiation direction of the ATSA to greatly enhance its radiation capability. We found that the proposed GRIN lens antenna has a wide impedance bandwidth of 175.7% (0.84 - 13 GHz) and -3 dB gain bandwidth of 65.8% (5.86 - 11.6 GHz). Its gain is averagely increased by 4.81 dB in the whole operating band, and the maximum gain reaches 20.55 dBi at 9.5 GHz. The simulation and measured results demonstrate that the designed GRIN lens antenna has excellent performance and is suitable for short-pulse ground penetrating radar systems. It also provides reference for other occasions that require high-gain and wideband antennas.

The Sichuan Basin magnetic anomaly is the most striking regional aeromagnetic anomaly in South China. It is characterized by a continuous large-scale linear magnetic anomaly and contains long-wavelength constituents which could still be detected on satellites. However, Sichuan Basin is covered by 4 to 10 km thick non-magnetic sedimentary layers from Neoproterozoic to Cenozoic, which conceals the magnetic sources in the Precambrian basement and makes it difficult to explore the geological origin of the Sichuan Basin magnetic anomaly. In this study, we applied 3D inversion to the magnetic data, and then compared our inverted susceptibility model with geological maps. We found that the spatial distribution of the Sichuan Basin magnetic anomaly controls the range of the rigid basement beneath Sichuan Basin and it is surrounded by the widespread Neoproterozoic magmatic complexes. Based on our analysis, we proposed that the geological origin of the Sichuan Basin magnetic anomaly might be related to the craton-scale Neoproterozoic magmatic event, which has played an important role in the stabilization of the basement and the evolution of the deep crust in Sichuan Basin.

Two subparallel east‐west trending linear aeromagnetic anomalies are observed along the central Yarlung‐Zangbo suture zone in southern Tibet. The Yarlung‐Zangbo suture zone represents the boundary of the Eurasian and Indian plates and records the subduction of the Neo‐Tethyan oceanic slab and subsequent continental collision. The two magnetic lineaments are spatially associated with the Gangdese batholith and Xigaze ophiolites, which are separated by the Xigaze fore‐arc basin that is filled with nonmagnetic sedimentary sequences. The Mesozoic‐Cenozoic Gangdese batholith is characterized by widespread I‐type granitoids. The Xigaze ophiolites are dominated by serpentinized mantle peridotites. To investigate the geological origins and deep structures of the magnetic sources of the two magnetic lineaments, a 3‐D inversion of aeromagnetic anomaly data was undertaken. By analyzing our inversion model and further magnetic modeling, it is proposed that the Gangdese batholith has a magmatic root with higher magnetization than the exposed granitoids, indicating that the deeper part of the Gangdese batholith may contain more mafic constituents than the shallow part. The subsurface part of the Xigaze ophiolites resembles a thin slab dipping to the south, implying that the deep‐seated Xigaze ophiolites are also serpentinized and retain complete structure.

Reduction to the pole (RTP) of magnetic anomalies has played a key role in the interpretation of magnetic anomalies. On a view of the development of RTP in frequency domain, we make a detailed analysis to the difficulty of RTP at low latitudes. A new suppression filter, which is deliberately designed to suppress specific frequencies to solve the problem, has fewer controlling parameters and is easy to operate and more direct compared with available filters. The tests on both synthetic data and practical data that are obtained in the area of low latitudes of the South China Sea demonstrate the effectiveness of this filter.