Tectonics of the offshore Red River Fault recorded in the junction of the Yinggehai and Qiongdongnan Basins

The Red River Fault,which originated from the southeastern margin of the Tibetan Plateau,has a great significance for obtaining a further understanding of the regional tectonics,topography and river catchment evolution,as well as the petroliferous sedimentary basin formation.The junction of the Yinggehai and Qiongdongnan Basins(YQB Junction)is the key to understanding when and how the strike-slip deformation on the South China Sea resulted from the collision between the Indian and Eurasian plates.In this study,we show regional seismic profiles,3D seismic and drilling core data to analyze the tectonostratigraphy in the YQB Junction,aiming to identify its tectonic framework and the associated faults system.A transitional domain from the strike-slip zone to the extensional deformation zone was mapped,which consisted of the No.1 Fault and the Zhongjian Uplift.The strike-slip faulting in the YQB Junction was active during the Oligocene-Early Miocene,with a period of strong faulting in the Early Oligocene.Integrated with the regional tectonic evolution,a coevolution model of strike-slip and extensional deformation in the YQB Junction and the adjacent area was built.In the Eocene,the YQB Junction was controlled by the NW-SE extension and formed a series of distributed rifts bounded by the NE-striking faults and filled up with proximal sediment.In the earliest Oligocene,a NW-trending strike-slip fault began to develop in the YQB Junction and crosscut the NEstriking normal faults.Since the occurrence of the strike-slip faults,the NE-striking faults,to the west of the No.1 Fault and the Zhongjian Uplift,failed to grow.However,to the east of the No.1 Fault and the Zhongjian Uplift,the faulting continued to develop until the latest Late Oligocene.The faulting of the NW-trending faults was observed to be active until the earliest Middle Miocene.Since then,with the exception of some diapiric structures and associated small-scale faulting in the Yinggehai Basin,we did not observe any basement-involved faulting.Our results will improve our understanding of the tectonics in the southeastern margin of the Tibetan Plateau and the South China Sea.

A square root information filter for multi-GNSS real-time precise clock estimation

Real-time satellite orbit and clock estimations are the prerequisite for Global Navigation Satellite System(GNSS)real-time precise positioning services.To meet the high-rate update requirement of satellite clock corrections,the computational efficiency is a key factor and a challenge due to the rapid development of multi-GNSS constellations.The Square Root Information Filter(SRIF)is widely used in real-time GNSS data processing thanks to its high numerical stability and computational efficiency.In real-time clock estimation,the outlier detection and elimination are critical to guarantee the precision and stability of the product but could be time-consuming.In this study,we developed a new quality control procedure including the three standard steps:i.e.,detection,identification,and adaption,for real-time data processing of huge GNSS networks.Effort is made to improve the computational efficiency by optimizing the algorithm to provide only the essential information required in the processing,so that it can be applied in real-time and high-rate estimation of satellite clocks.The processing procedure is implemented in the PANDA(Positioning and Navigation Data Analyst)software package and evaluated in the operational generation of real-time GNSS orbit and clock products.We demonstrated that the new algorithm can efficiently eliminate outliers,and a clock precision of 0.06 ns,0.24 ns,0.06 ns,and 0.11 ns can be achieved for the GPS,GLONASS,Galileo,and BDS-2 IGSO/MEO satellites,respectively.The computation time per epoch is about 2 to 3 s depending on the number of existing outliers.Overall,the algorithm can satisfy the IGS real-time clock estimation in terms of both the computational efficiency and product quality.

Investigating GNSS PPP-RTK with external ionospheric constraints

Real-Time Kinematic Precise Point Positioning(PPP–RTK)is inextricably linked to external ionospheric information.The PPP-RTK performances vary much with the accuracy of ionospheric information,which is derived from diferent network scales,given diferent prior variances,and obtained under diferent disturbed ionospheric conditions.This study investigates the relationships between the PPP–RTK performances,in terms of precision and convergence time,and the accuracy of external ionospheric information.The statistical results show that The Time to First Fix(TTFF)for the PPP-RTK constrained by Global Ionosphere Map(PPP-RTK-GIM)is about 8–10 min,improved by 20%–50%as compared with that for PPP Ambiguity Resolution(PPP-AR)whose TTFF is about 13–16 min.Additionally,the TTFF of PPP-RTK is 4.4 min,5.2 min,and 6.8 min,respectively,when constrained by the external ionospheric information derived from diferent network scales,e.g.small-,medium-,and large-scale networks,respectively.To analyze the infuences of the optimal prior variances of external ionospheric delay on the PPP–RTK results,the errors of 0.5 Total Electron Content Unit(TECU),1 TECU,3 TECU,and 5 TECU are added to the initial ionospheric delays,respectively.The corresponding convergence time of PPP–RTK is less than 1 min,about 3,5,and 6 min,respectively.After adding the errors,the ionospheric information with a small variance leads to a long convergence time and that with a larger variance leads to the same convergence time as that of PPP-AR.Only when an optimal prior variance is determined for the ionospheric delay in PPP-RTK model,the convergence time for PPP-RTK can be shorten greatly.The impact of Travelling Ionospheric Disturbance(TID)on the PPP-RTK performances is further studied with simulation.It is found that the TIDs increase the errors of ionospheric corrections,thus afecting the convergence time,positioning accuracy,and reliability of PPP-RTK.