Academia still has different opinions on whether there is a consecutive central uplift belt in the Qiangtang Basin.The latest high-precision airborne gravity and aeromagnetic data provided in this article verify the existence of the central uplift belt,which is controlled by two faults,traversing the Qiangtang Basin from east to west.A set of near-north-south left-lateral slip fault systems divide this uplift belt into several parts.The uplift belt,gradually converged from west to east,has obviously different characteristics between the east and west sides of Shuanghu County.The west section shows large-scale uplift of the basement,and the bedrock depth is generally within 3~5 km,which is much shallower than those in the North and South Qiangtang depression with the basement depth of 7~15 km.However,the uplift amplitude of the eastern segment decreases significantly,mainly manifested as a low base uplift.In addition,the central uplift belt shows obvious“multi-segments”and“step-like”decreasing trend from west to east,controlled by near-north-south faults.The basement depth of the Shuanghu-Yaqu section is between 5 and 7 km,and that of the Yaqu-Gonney section is between 7 and 9km.According to the structural stratification comparison,it is reveraled that the North Qiangtang Block has a smaller uplift amplitude and better stability than the South Qiangtang Block.The differences in geophysical properties of the basement between the North and South Qiangtang depression indicate that there is not an unified Precambrian metamorphic basement in the Qiangtang Basin,and the formation of the central uplift zone may be related to the melange zone formed during the closure of the Paleo-Tethys Ocean.

Abstract Because the sensitivity of the disturbing intersatellite range measurements to the recovery accuracy of the Earth's gravitational field is superior to that of the intersatellite range measurements, the observation equation of a new Disturbing Intersatellite Range Method (DIRM) is created in this study. Then the orbital stability of the next‐generation Hybrid‐Inline‐Pendulum‐Three‐Satellite (HIP‐3S) formation is efficiently verified. The research results indicate that the HIP‐3S formation is sufficiently steady for further enhancing the accuracy of the future Earth gravity field model. Finally, the Earth's gravitational field complete up to degree and order 120 is precisely recovered by the current GRACE‐2S inline formation and the next‐generation HIP‐3S combined formation based on the new DIRM, and the cumulative geoid height errors are 2.271×10−1 m and 1.923×10−3 m at degree 120, respectively. The study results show that the future HIP‐3S formation is helpful for producing the next‐generation Earth gravity field model with higher accuracy and spatial resolution.

Abstract The lithosphere‐asthenosphere boundary (LAB) is a seismic discontinuity with negative velocity contrast in the upper mantle. Seismic detections of the LAB in subduction zone region are helpful to understand the interaction between the lithosphere and asthenosphere and the geodynamic process associated with the slab subduction. In this paper, the vertical broadband waveforms are collected from four deep earthquakes occurred from 2006 to 2012 beneath the central South America area. The seismic waveforms are processed with the linear slant stack method to get the vespagrams in the relative travel‐time vs. slowness domain, and the sP precursors reflected at the bottom of the LAB (sLABP) are successfully extracted. Based on the one‐dimensional modified velocity model (IASP91‐SA), the horizontal distribution for the six sLABP reflecting points is obtained and divided into the western part (I) and the eastern part (II). In the part I, the LAB depth ranges between 60 km and 63 km, with the average depth of 61 km and the topography of 3 km; in the part II, the LAB depth ranges between 78 km and 82 km, with the average depth of 80 km and the topography of 4 km. Our results reveal the increasing LAB depths from west to east in the central South America area, and the trend may possibly represent the reformation differences of the continental lithosphere. We infer that near the trench, the continental lithosphere may be subjected to the stronger erosion for the higher degree of partial melting and more fertile melts in the asthenosphere; while far from the trench, the continental lithosphere may be subjected to the weaker erosion for the lower degree of partial melting and less fertile melts in the asthenosphere.

Abstract Cavernous carbonate formations are characterized by strong heterogeneity, which results in the complex electric logging responses and the difficulty in the logging identification and evaluation. Numerical simulation of electric logging tools is helpful to figure out the logging response characteristics in these formations and could provide theoretical support for cave recognition and evaluation. In this paper, based on three dimensional finite element methods, a local refinement technique is adopted for the accurate discretization and simulation of complex sphere caves. Then, the response characteristics and sensitivity of dual laterolog to caves around and penetrated by wellbore are analyzed, finally the differences of sensitive scope between deep and shallow laterolog are studied. The results show that the dual laterolog response decreases significantly when cave exists. Affected by cave boundary and the investigation depth of dual laterolog tool, the logging response for caves penetrated by wellbore is very complicated, however it exhibits parabolic‐like characteristic for caves around wellbore. Compared with caves around wellbore, the dual laterolog is much more sensitive to caves penetrated by wellbore. For caves around wellbore, the maximum sensitive distance for deep and shallow laterolog between the cave boundary and well wall is 0.5 m and 0.3 m, respectively.

Abstract More than 20000 dayside auroral arcs of the 557.7 and 630.0 nm emission intensities have been statistically studied, and the dependences of the I557.7/I630.0 ratio on the I557.7 emission intensity have been determined. The 557.7 nm emission intensity has two maximum values in the hot spot and warm spot regions, with average values of 2.2 and 2.9 kR, respectively. But there is a maximum near magnetic noon for 630.0 nm emission intensity, with an average value of 1.5 kR. In the I557.7 emission range 0.1∼10 kR, the I557.7/I630.0 ratio tends to increase from 0.2 to 9. The correlation between emission intensity and precipitating electron spectra has been investigated using 17 cases of DMSP passing through 40 auroral arcs above Chinese Arctic Yellow River Station (YRS). We obtain the equations that the average energy of the electrons is proportional to the I557.7/I630.0 ratio. There is a positive correlation between the total energy flux of the electrons and the I557.7 emission intensity. The typical region of electron precipitation, where the auroral arcs were observed, was the boundary plasma sheet (BPS) in the prenoon and postnoon sectors. We also found some low‐energy precipitating electrons from the region of mantle, where the arcs are located poleward of dayside auroral oval. The magnetic source region of the precipitating electrons with low energy was identified as the low latitude boundary layer (LLBL) adjacent to magnetic noon. Arcs are located in the lower latitude in this region.

Full-polarimetric ground penetrating radar (GPR) can obtain the co-polarization and cross-polarization information simultaneously,which can help to understand the target attribute better.A forward modeling algorithm for the full polarization GPR is developed using finite-difference time-domain (FDTD) method in this paper.The full polarization information is simulated by setting transmitting antenna and receiving antenna in horizontal and orthogonal directions.A metal plate and a corner reflector are used as targets.The simulation results show good coincidence to the results obtained by model experiment.Furthermore,the responses of random surface and oblique fracture are simulated,and good results are obtained.Both simulation and experiment results show that full polarization information will help us to identify target attributes such as the shape,structure,orientation and physical properties.