ALBERT

Description: Earthquakes are generally known to alter the stress field near seismogenic faults. Observations using YRY-four-gauge borehole strainmeters within Yushu (YSH) borehole near the Ganzi-Yushu fault in eastern Tibetan Plateau shows that the azimuth variation of maximum horizontal stress (SH) first decreased and then increased substantially when the earthquakes occurred during the measurement period from January 1, 2009 to December 31, 2018. In this period, 38 earthquakes (M ≥ 3) were detected near the fault and the SH orientation showed a drastic change after the 2010 Ms 7.3 Yushu mainshock. We present a discrete element modelling using Particle Flow Code 2D (PFC2D) to simulate a dynamic fault rupturing process and to use the modelling results for interpretation of the stress reorientation. The modelling reveals that dilatation and compression quadrants are formed around a fault rupturing in strike-slip model, resulting in different spatiotemporal changes of the orientation of maximum horizontal stress (Δθ). The value of Δθ in the compression quadrants shows a sharp drop at the time of coseismic slip, then approaches slowly to an asymptotic value. In the dilatation quadrants, Δθ drops by coseismic slip, then increases sharply and finally reaches a stable value. The modelled Δθ by coseismic fault slip agrees with in-situ observations at YSH borehole during 2010 Ms 7.3 Yushu mainshock. It is also found that, the value of Δθ decreases with increasing distance from the rupturing source. We modelled the effect of fault geometry and host rock properties on the Δθ, and found that structural complexity and off-fault damage by coseismic fault slip have significant impact on the stress field alteration near the rupturing source.

Description: To solve the problem that integer ambiguity between middle-range reference stations in BDS is difficult to be fixed correctly due to the influence of ionospheric delay error and tropospheric delay error, an algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations was proposed. Firstly, the frequency observations of B2 and B3 were used to determine B2-B3 extra-wide-lane integer ambiguity. Then, B1-B3 wide-lane integer ambiguity was solved by using the closer characteristic of ionospheric delay error between B2-B3 extra-wide-lane and B1-B3 wide-lane combination observation, and B1-B2 wide-lane integer ambiguity can be fixed according to the linear relationship of triple-frequency integer ambiguity. Furthermore, B1-B3 and B1-B2 ionosphere-free combination observation and the decomposable characteristic of the corresponding integer ambiguity were used to estimate narrow-lane integer ambiguity and relative zenith tropospheric delay error, and then narrow-lane integer ambiguity can be finally fixed by search mode. This algorithm is tested by the measured triple-frequency data of BDS CORS network. The results show that triple-frequency carrier phase integer ambiguity between middle-range BDS reference stations can be fixed accurately and effectively with the method. © 2021, Editorial Board of Journal of CUMT. All right reserved. Search Sources Lists SciVal ALBERT Telegrafenberg Holdings (Opens new window) Alerts Document details - The algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations Back to results Previous 3of20 Next SFX Get it!(opens in a new window)|Entitled full text| Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and TechnologyVolume 50, Issue 2, Pages 396 - 403March 2021 Document type Article Source type Journal ISSN 10001964 The algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations[BDS中距离参考站三频整周模糊度确定方法] a , a, a, b, a To solve the problem that integer ambiguity between middle-range reference stations in BDS is difficult to be fixed correctly due to the influence of ionospheric delay error and tropospheric delay error, an algorithm of triple-frequency integer ambiguity resolution between middle-range BDS reference stations was proposed. Firstly, the frequency observations of B2 and B3 were used to determine B2-B3 extra-wide-lane integer ambiguity. Then, B1-B3 wide-lane integer ambiguity was solved by using the closer characteristic of ionospheric delay error between B2-B3 extra-wide-lane and B1-B3 wide-lane combination observation, and B1-B2 wide-lane integer ambiguity can be fixed according to the linear relationship of triple-frequency integer ambiguity. Furthermore, B1-B3 and B1-B2 ionosphere-free combination observation and the decomposable characteristic of the corresponding integer ambiguity were used to estimate narrow-lane integer ambiguity and relative zenith tropospheric delay error, and then narrow-lane integer ambiguity can be finally fixed by search mode. This algorithm is tested by the measured triple-frequency data of BDS CORS network. The results show that triple-frequency carrier phase integer ambiguity between middle-range BDS reference stations can be fixed accurately and effectively with the method. © 2021, Editorial Board of Journal of CUMT. All right reserved.