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Using the Data from One Receiver to Estimate Running Velocity of High-Speed Train
WANG Xiaokai, WANG Baoli, CHEN Wenchao, LI Jiaqi
Acta Scientiarum Naturalium Universitatis Pekinensis    2019, 55 (5): 798-804.   DOI: 10.13209/j.0479-8023.2019.071
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Based on the fixed carriage structure assumption, the acquired dataset from one receiver near the highspeed railway can be used to estimate running velocity of high-speed train (HST). We derive the relationship between the load function and the speed of the railway, and then propose the HST velocity estimating method based on velocity scanning. Firstly, this method generates a series of amplitude spectra of load function according to a series of preset velocity. Then a series of cross-correlation coefficients between the pre-computed amplitude spectra and the amplitude spectrum of the real signal from one pre-buried receiver can be computed. The velocity with maximum cross-correlation coefficients is chosen as a final velocity estimation of HST. Finally, one synthetic data example and some real data examples illustrate our method’s effectiveness. Furthermore, the proposed method has the potential to be further extended to estimate running velocity of moving objects with the fixed structure in other road traffic.
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Theoretical Investigation on Earthquake Source Spectra Isolation by Iteratively Stacking Separation
LI Jiaqi, WANG Shuguang, NING Jieyuan
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (3): 427-436.   DOI: 10.13209/j.0479-8023.2016.042
Abstract1021)   HTML    PDF(pc) (636KB)(848)       Save

The correctness of the earthquake source spectra derived from array data with an iteratively stacking method is checked by analyzing the expressions of iterative stacking in each step. The expression of the finally derived source spectra term shows that it has nothing of the station term, but will be affected by the path term dependent on the source-receiver configuration, which is further confirmed by numerical simulations with iteratively stacking method. Considering stress drop might be wrongly estimated when stations or events are unevenly distributed, the paper provides a strategy to derive the correct stress drop in typical conditions of stationevent configurations. It will be helpful to correctly acquire seismic source information from seismic data.

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A Computational Scheme for Quantitatively Removing the Effects of Lateral Velocity Variation on 1-D Triplicated Wave Velocity Inversion
LI Jiaqi, WANG Shuguang, CAI Chen, NING Jieyuan
Acta Scientiarum Naturalium Universitatis Pekinensis    2016, 52 (3): 420-426.   DOI: 10.13209/j.0479-8023.2016.041
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Theoretical analysis quantitatively shows that high velocity anomaly near source, low velocity anomaly near receiver and the lateral velocity variation above the target inversion area have the influence of the same dimension of anomaly on the traditional inversion of 1-D wave velocity by triplicated wave arrival times. A quantitative computation scheme is proposed to remove the smearing effects with the help of regional or global tomography results when using 1-D inversion by triplicated wave arrival times. Tests imply that the velocity smearing could be eliminated to great extent and the real 1-D structure might be recovered.

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