# 시추공 3성분 계측 현장실험을 통한 미소지진 모니터링 정확도 향상 연구

• Accepted : 2016.12.12
• Published : 2017.02.28

#### Abstract

In order to improve the accuracy of microseismic epicenter location through the inversion techniques using P and S wave first arrivals, field experiments of microseismic monitoring were performed using borehole 3-component geophones. The direction of epicenter was estimated from the hodograms of P-wave first arrivals through the weight drop experiments in which the $\times$ component of 3-component geophone was aligned to the magnetic north. The picking of S wave first arrival was possible in the polarization filtered data even if S waves are difficult to be identified in raw data. The inversion technique using only P wave first arrival times can often converge to the local minimum when the initial values for epicenter are largely apart from the true epicenter, so that the correct solution can not be found. To solve this problem, the epicenter determination method using differences between P and S wave arrival times was used to estimate proper initial values of epicenter. The inversion result using only P-wave first arrival times which started from the estimated initial values showed the improved accuracy of the epicenter location.

#### Acknowledgement

Grant : 셰일가스 파쇄효율 향상을 위한 탐사프 로세스 및 실증연구

Supported by : 한국에너지기술평가원

#### References

1. Eisner, L., Duncan, P. M., Heigl, W. M., and Keller, W. R., 2009, Uncertainties in passive seismic monitoring, The Leading Edge, 28(6), 648-655. https://doi.org/10.1190/1.3148403
2. Flinn, E. A., 1965, Signal analysis using rectilinearity and direction of particle motion, Proc. IEEE, 53, 1874-1876. https://doi.org/10.1109/PROC.1965.4462
3. FURUNO, 2016, http://www.furuno.com/en/gnss/case/furuno03 (November 11, 2016 Accessed)
4. Jones, G. A., Raymer, D., Chambers, K., and Kendall, J. M., 2010, Improved microseismic event location by inclusion of a priori dip particle motion: a case study form Ekofisk, Geophysical Prospecting, 58, 727-737. https://doi.org/10.1111/j.1365-2478.2010.00873.x
5. Kim, J. Y., 2011, Development of optimum monitoring system for ground subsidence, MIRECO REPORT, 211-117, 335-338.
6. Kim, D. W., Kim, M. S., Byun, J. M., and Seol, S. J., 2015, Locating microseismic events using a single vertical well data, Geophysics and Geophysical Exploration, 18, 64-73. https://doi.org/10.7582/GGE.2015.18.2.064
7. Montalbetti, J. R., and Kanasewich, E. R., 1970, Enhancement of teleseismic body phases with a polarization filter, Geophys. J. R. Astr. Soc., 21, 119-129. https://doi.org/10.1111/j.1365-246X.1970.tb01771.x
8. Warpinski, N. R., Sullivan, R. V., Uhl, J. E., Waltman, C. K., and Machovoe, S. R., 2003, Improved microseiscmic fracture mapping using perforation timing measurements for velocity calibration, SPE Annual Technical Conference and Exhibition, 5-8 October, Denver, Colorado.