Properties of Noise Cross Correlation Functions Obtained from a Distributed Acoustic Sensing (DAS) Array at Garner Valley, California

  • 邓春林
  • 创建于 2016-03-10

报 告 人:曾祥方 博士 Department of GeoscienceUniversity of Wisconsin-Madison 报告时间:2016年1月18日(周 一)14:00—15:00 报告地点:中科院计算地球动力学重点实验室会议室 中国科学院大学科研楼西楼106室 报告简介: The field test of Distributed Acoustic Sensing (DAS) conducted at Garner Valley, California on September 11-12, 2013 provided a continuous overnight record of ambient noise. The DAS array recorded ground motions every one meter of optical cable that was arranged approximately in the shape of a rectangle with dimensions of 160 m by 80 m. The long dimension of the array was adjacent to a state highway. Three hours of record were used to compute noise cross-correlation functions (NCFs) in one-minute windows. The trace from each sensor channel was pre-processed by downsampling to 200 Hz, followed by normalization in the time-domain and bandpass filtering between 2 and 20 Hz (Bensen et al., 2007). The one-minute NCFs were then stacked using the time-frequency domain phase-weighted stacking method (Schimmel & Gallart, 2007). The NCFs between channels were asymmetrical reflecting the direction of traffic noise. The group velocities were found using the frequency-time analysis method. The energy was concentrated between 5 and 15 Hz, which falls into the typical traffic noise frequency band. The resulting velocities were between 100 and 300 m/s for frequencies between 10 and 20 Hz, which are in the same range as described in the results for surface-wave dispersion obtained using an active source for the same site (Lancelle et al., 2015). The group velocity starts to decrease for frequencies greater than ~10 Hz, which was expected on the basis of a previous shear-wave velocity model (Steidl et al., 1996). Then, the phase velocity was calculated using the multichannel analysis of surface wave technique (MASW - Park et al., 1999) with 114 NCFs spaced one meter apart. The resulting dispersion curve between 5 and 15 Hz gave phase velocities that ranged from approximately 170 m/s at 15 Hz to 250 m/s at 5 Hz. These results are consistent with other results of active-source DAS and seismometer records obtained at the Garner Valley site (e.g., Stokoe et al. 2004). 报告人简介: Education: University of Science and Technology of China (USTC) Ph D., Sept. 2006 – Jul. 2012 Major: Geophysics University of Science and Technology of China (USTC) Bachelor of Science, Sept. 2002 – Jul. 2006 Major: Geophysics Minor: Finance Experience: Nov. 2013 -- Postdoctoral Associate Department of Geoscience, University of Wisconsin-Madison Feb. 2012 -- Postdoctoral CAS Key Lab of Computational Geodynamics, University of Chinese Academy of Sciences Sept.2006 – Jan. 2012 Graduate student School of Earth and Space Sciences, University of Science and Technology of China Sept. 2008 – Sept. 2009 Visiting student Earth Resource Laboratory, Massachusetts Institute of Technology Sept. 2002 – Jul. 2006 Undergraduate student School of Earth and Space Sciences, University of Science and Technology of China Professional Societies: American Geophysical Union, Student member (2008- ) Research Fields: Seismic structure Distributed acoustic sensing Source parameters of earthquake Seismic ambient noise source Publications: 2015 Zeng, X., C. 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Ni (2010) A persistent localized microseismic noise source near Kyushu Island Japan. Geophys. Res. Lett., 37,L24307. Luo Y., S. Ni, X. Zeng, Y. Zheng, Q. Chen, and Y. Chen (2010) A shallow aftershock sequence in the north-esatern end of the Wenchuan earthquake aftershock zone. Sci China D: Earth Sci., 53(11): 1655-1664. Chong J. S. Ni, and X. Zeng (2010) sPL, an effective seismic phase for determining focal depth at near distance, Chinese J. Geophys. (in Chinese), 53(11): 2620-2630. Wan K., S. Ni, X. Zeng, and P. Sommerville (2009) Real-time seismology for the 05/12/2008 Wenchuan earthquake of China, a retrospective view. Sci China D: Earth Sci., 52(2): 155-165.