Ye F.,Jilin University |
Ye F.,National Geophysical Exploration Instrument Engineering Technology Research Center |
Lin J.,Jilin University |
Lin J.,National Geophysical Exploration Instrument Engineering Technology Research Center |
And 4 more authors.
International Journal of Earth Sciences and Engineering | Year: 2015
With the application of broadband seismic instruments, ambient seismic noise is being gradually applied to the development of seismological studies. In particular, a broadband seismic instrument as a monitoring tool can be used to explore weak physical change in the medium through a long period of recording. However, previous studies have revealed that instrument time error is an important interfering factor which cannot be directly distinguished. In this paper, cross-spectral analysis is proposed to detect instrument time error using ambient seismic noise. The method is based on comparisons between the reference surface wave stacked by a long period and the daily surface wave to calculate the time difference between each pair of stations for the direct surface wave can be retrieved from the cross-correlation of ambient seismic noise. In our experiments, we applied the proposed method to the whole year of continuous ambient noise records at 18 broadband stations in California. The joint analysis of multiple stations allows us to evaluate instrument time error in order to avoid the inference of physical change. For there is no removal of the instrument response, we found that the mean values of time difference between each pair of stations was no more than the order of 0.01s and met the verification principle of the closure relations between triplets of stations. However, the time difference shows significant variations in several pairs of stations. The instrument time error of an individual station is obtained with a standard deviation value of 0.01s by least-squares inversion for time differences between station pairs. The clear fluctuation of instrument time error is identified in individual stations. Different from generally used time symmetry analysis, the technique overcomes the restriction of the ambient noise cross-correlation functions being asymmetric in time and has better time resolution for a moving 10-day window. © 2015 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
Jia Z.,Jilin University |
Jia Z.,National Geophysical Exploration Instrument Engineering Technology Research Center |
Li Z.,Jilin University |
Li Z.,National Geophysical Exploration Instrument Engineering Technology Research Center |
And 6 more authors.
Instrumentation Science and Technology | Year: 2015
Monitoring of fracture orientation is of significance in the exploration and development of coal-bed methane; for this purpose, a monitoring system, based on the principle of differential electric resistivity tomography, has been widely used. The resolution and monitoring scope determine the detection depth of the coal-bed methane fracturing layer. In this article, a coal-bed methane fracture monitoring system with a resolution of less than approximately 10 μV and 90 channels is reported using virtual instrument technology. Based on the three-dimensional geoelectric field of vertical finite line source by the finite-difference method, the surface potential difference between different depths and the scope of surface fracture anomaly was calculated, which demonstrated the feasibility of this system. The system exhibited satisfactory performance for a coal-bed methane well in Jixian, Shanxi Province. Compared with a microseismic monitoring system, the coal-bed methane fracture system was more convenient and achieved similar results of fracture orientations at a depth of 1263 m. Moreover, it avoided the uncertainty of a single method. Therefore, it is expected that this system may be widely applied to the fracture monitoring of coal-bed methane. Copyright © Taylor & Francis Group, LLC.
Gao N.,Jilin University |
Gao N.,National Geophysical Exploration Instrument Engineering Technology Research Center |
Zheng F.,Jilin University |
Zheng F.,National Geophysical Exploration Instrument Engineering Technology Research Center |
And 6 more authors.
Instrumentation Science and Technology | Year: 2016
Seismic exploration is widely used in mining projects. A cable-free self-positioning seismograph has been developed by College of Instrumentation & Electrical Engineering of Jilin University that may collect and store seismic data wirelessly or by Ethernet. When large data sets are produced, data download may affect the schedule of a project. To improve the rate of transfer, a system that allows parallel download of multichannel seismic data is reported here. The system is based on private cloud technology and proportional integral derivative control. A private cloud was employed to provide suitable performance and availability. A proportional integral derivative control algorithm was developed for scheduling to maintain the load balance of the system. The system was employed in a seismic exploration project in Liaoning, China. The average download time of six lines was approximately 1.1 hours, demonstrating that the system reduced download time and enhanced exploration efficiency. © 2016 Taylor & Francis Group, LLC.