To overcome the shortcomings of the traditional multibeam survey and data processing, a new method is presented for the precise determination of the instantaneous height at the multibeam transducer by the blend of GPS...To overcome the shortcomings of the traditional multibeam survey and data processing, a new method is presented for the precise determination of the instantaneous height at the multibeam transducer by the blend of GPS height and heave signals. Before signal blend, GPS height and heave signals need to be corrected first to the transducer center by attitude correction. Second, the GPS height needs to be checked and modified by heave check and modification itself. Butterworth and FFT （fast Fourier transformation） were used in the signal blend. Finally, FFT is thought to be appropriate in signal processing. The new method efficiently overcomes the shortcomings of the traditional method, and this is proven well by the MBS （multibeam bathymetric system） experiment.展开更多
The discontinuous Galerkin （DO） or local discontinuous Galerkin （LDG） method is a spatial discretization procedure for convection-diffusion equations, which employs useful features from high resolution finite volu...The discontinuous Galerkin （DO） or local discontinuous Galerkin （LDG） method is a spatial discretization procedure for convection-diffusion equations, which employs useful features from high resolution finite volume schemes, such as the exact or approximate Riemann solvers serving as numerical fluxes and limiters. The Lax- Wendroff time discretization procedure is an altemative method for time discretization to the popular total variation diminishing （TVD） Runge-Kutta time discretizations. In this paper, we develop fluxes for the method of DG with Lax-Wendroff time discretization procedure （LWDG） based on different numerical fluxes for finite volume or finite difference schemes, including the first-order monotone fluxes such as the Lax-Friedfichs flux, Godunov flux, the Engquist-Osher flux etc. and the second-order TVD fluxes. We systematically investigate the performance of the LWDG methods based on these different numerical fluxes for convection terms with the objective of obtaining better performance by choosing suitable numerical fluxes. The detailed numerical study is mainly performed for the one-dimensional system case, addressing the issues of CPU cost, accuracy, non-oscillatory property, and resolution of discontinuities. Numerical tests are also performed for two dimensional systems.展开更多
The seismic waveform of the Yutian Ms7. 3 earthquake, Xinjiang on February 12, 2014 was recorded clearly and completely by the Digital Seismic Networks of Xinjiang, Qinghai, Tibet, and Xinjiang Hotan array, so the met...The seismic waveform of the Yutian Ms7. 3 earthquake, Xinjiang on February 12, 2014 was recorded clearly and completely by the Digital Seismic Networks of Xinjiang, Qinghai, Tibet, and Xinjiang Hotan array, so the method of joint location by regional seismic network and seismic array can be used to accurately determine the earthquake source location. The following technologies were used in the process of location： （ 1 ） We selected seismic stations equally located around the epicenter of the Ms 7. 3 earthquake with an average interval of about 15 degrees in the initial location. （2） The recording waveforms of Yutian seismic station were rotated to the radial and tangential directions to precisely obtain the arrival time of S-waves to determine the epicentral distance. （ 3） The velocity model was used in the determination of location of the epicenter, based on the historical records of earthquakes in the area within a radius of 1.0 ° from the source as the center, and the velocity model is obtained after re-fitting and calibration. （4） Based on the waveform records of the Hotan seismic array, the method of waveform beaming was used to determine the azimuths and perform the correction of the epicenter location with these azimuths. （5） The deterministic method was used to measure the source depth. Finally, it is concluded that the Yutian Ms 7. 3 main shock hypocenter location is 36. 197°N, 82. 467°E, focal depth 12km and original time 17：19：48. 2 μm. February 12, 2014.展开更多
Five mobile digital seismic stations were set up by the Earthquake Administration of Yunnan Province near the epicenter of the main shock after the Ning＇er M6. 4 earthquake on June 3, 2007. In this paper, the aftersh...Five mobile digital seismic stations were set up by the Earthquake Administration of Yunnan Province near the epicenter of the main shock after the Ning＇er M6. 4 earthquake on June 3, 2007. In this paper, the aftershock sequence of the Ning＇er M6. 4 earthquake is relocated by using the double difference earthquake location method. The data is from the 5 mobile digital seismic stations and the permanent Simao seismic station. The results show that the length of the aftershock sequence is 40kin and the width is 30km, concentrated obviously at the lateral displacement area between the Pu＇er fault and the NNE-trending faults, with the majority occurring on the Pu＇er fault around the main shock. The depths of aftershocks are from 2kin to 12km, and the predominant distribution is in the depth of 8 ~ 10km. The mean depth is 7. 9kin. The seismic fault dips to the northwest revealed from the profile parallel to this aftershock sequence, which is identical to the dip of the secondary fault of the NE-trending Menglian-Mojiang fault in the earthquake area. There are more earthquakes concentrated in the northwest segment than in the southeast segment, which is perhaps related to the underground medium and faults. The depth profile of the earthquake sequence shows that the relocated earthquakes are mainly located near the Pu＇er fault and the seismic faults dip to the southwest, consistent with the dip of the west branch of the Pu＇er fault. In all, the fault strike revealed by earthquake relocations matches well with the strike in the focal mechanism solutions. The main shock is in the top of the aftershock sequence and the aftershocks are symmetrically distributed, showing that faulting was complete in both the NE and SW directions.展开更多
基金Funded by the National Natural Science Foundation of China （No.40776048）
文摘To overcome the shortcomings of the traditional multibeam survey and data processing, a new method is presented for the precise determination of the instantaneous height at the multibeam transducer by the blend of GPS height and heave signals. Before signal blend, GPS height and heave signals need to be corrected first to the transducer center by attitude correction. Second, the GPS height needs to be checked and modified by heave check and modification itself. Butterworth and FFT （fast Fourier transformation） were used in the signal blend. Finally, FFT is thought to be appropriate in signal processing. The new method efficiently overcomes the shortcomings of the traditional method, and this is proven well by the MBS （multibeam bathymetric system） experiment.
基金supported by the European project ADIGMA on the development of innovative solution algorithms for aerodynamic simulations,NSFC grant 10671091,SRF for ROCS,SEM and JSNSF BK2006511.
文摘The discontinuous Galerkin （DO） or local discontinuous Galerkin （LDG） method is a spatial discretization procedure for convection-diffusion equations, which employs useful features from high resolution finite volume schemes, such as the exact or approximate Riemann solvers serving as numerical fluxes and limiters. The Lax- Wendroff time discretization procedure is an altemative method for time discretization to the popular total variation diminishing （TVD） Runge-Kutta time discretizations. In this paper, we develop fluxes for the method of DG with Lax-Wendroff time discretization procedure （LWDG） based on different numerical fluxes for finite volume or finite difference schemes, including the first-order monotone fluxes such as the Lax-Friedfichs flux, Godunov flux, the Engquist-Osher flux etc. and the second-order TVD fluxes. We systematically investigate the performance of the LWDG methods based on these different numerical fluxes for convection terms with the objective of obtaining better performance by choosing suitable numerical fluxes. The detailed numerical study is mainly performed for the one-dimensional system case, addressing the issues of CPU cost, accuracy, non-oscillatory property, and resolution of discontinuities. Numerical tests are also performed for two dimensional systems.
基金funded by the Special Project of the Department of Earthquake Monitoring and Prediction,China Earthquake Administration(1309010)Seismic Network Youth Special Project,China Earthquake Administration(20140330,20130201)
文摘The seismic waveform of the Yutian Ms7. 3 earthquake, Xinjiang on February 12, 2014 was recorded clearly and completely by the Digital Seismic Networks of Xinjiang, Qinghai, Tibet, and Xinjiang Hotan array, so the method of joint location by regional seismic network and seismic array can be used to accurately determine the earthquake source location. The following technologies were used in the process of location： （ 1 ） We selected seismic stations equally located around the epicenter of the Ms 7. 3 earthquake with an average interval of about 15 degrees in the initial location. （2） The recording waveforms of Yutian seismic station were rotated to the radial and tangential directions to precisely obtain the arrival time of S-waves to determine the epicentral distance. （ 3） The velocity model was used in the determination of location of the epicenter, based on the historical records of earthquakes in the area within a radius of 1.0 ° from the source as the center, and the velocity model is obtained after re-fitting and calibration. （4） Based on the waveform records of the Hotan seismic array, the method of waveform beaming was used to determine the azimuths and perform the correction of the epicenter location with these azimuths. （5） The deterministic method was used to measure the source depth. Finally, it is concluded that the Yutian Ms 7. 3 main shock hypocenter location is 36. 197°N, 82. 467°E, focal depth 12km and original time 17：19：48. 2 μm. February 12, 2014.
基金sponsored by the Joint Earthquake Science Foundation,China (200804)
文摘Five mobile digital seismic stations were set up by the Earthquake Administration of Yunnan Province near the epicenter of the main shock after the Ning＇er M6. 4 earthquake on June 3, 2007. In this paper, the aftershock sequence of the Ning＇er M6. 4 earthquake is relocated by using the double difference earthquake location method. The data is from the 5 mobile digital seismic stations and the permanent Simao seismic station. The results show that the length of the aftershock sequence is 40kin and the width is 30km, concentrated obviously at the lateral displacement area between the Pu＇er fault and the NNE-trending faults, with the majority occurring on the Pu＇er fault around the main shock. The depths of aftershocks are from 2kin to 12km, and the predominant distribution is in the depth of 8 ~ 10km. The mean depth is 7. 9kin. The seismic fault dips to the northwest revealed from the profile parallel to this aftershock sequence, which is identical to the dip of the secondary fault of the NE-trending Menglian-Mojiang fault in the earthquake area. There are more earthquakes concentrated in the northwest segment than in the southeast segment, which is perhaps related to the underground medium and faults. The depth profile of the earthquake sequence shows that the relocated earthquakes are mainly located near the Pu＇er fault and the seismic faults dip to the southwest, consistent with the dip of the west branch of the Pu＇er fault. In all, the fault strike revealed by earthquake relocations matches well with the strike in the focal mechanism solutions. The main shock is in the top of the aftershock sequence and the aftershocks are symmetrically distributed, showing that faulting was complete in both the NE and SW directions.
