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http://dx.doi.org/10.5000/EESK.2019.23.6.321

Characterizing the Performance of New Seismic Stations in Southeastern Region, Korea Using Seismic Noise Levels  

Shin, Jin Soo (Earthquake Research Center, Korea Institute of Geoscience and Mineral Resources)
Seong, Yun-Jeong (Earthquake Research Center, Korea Institute of Geoscience and Mineral Resources)
Son, Minkyung (Earthquake Research Center, Korea Institute of Geoscience and Mineral Resources)
Publication Information
Journal of the Earthquake Engineering Society of Korea / v.23, no.6, 2019 , pp. 321-327 More about this Journal
Abstract
We performed seismic noise level analysis to access the proper functioning of 11 newly established seismic stations in the southeastern region of Korea. One-hour long segments of seismograms were selected from the continuous data of the 3 elements for 61 days from March 1, 2019. For each segment of data, the power spectral density (PSD) was estimated from the continuous back ground noise data of the 3 elements for periods ranging from 0.02~100 s. The median noise levels (NLs) of the stations were compared with the new noise model (NNM) of USGS and NLs of station TJN installed in a tunnel on a granite basement. We observed that the NLs of the newly installed seismometers were between the upper and lower limit of the NNM. In a comparison with the noise level of station TJN, the new seismometers had their own noteworthy features. The NLs from accelerometers (Epi-sensors) were ~ 40 dB higher than the NLs from velocimeters (STS-sensors) for periods > 10 s, which is because the small and light Epi-sensors are sensitive to environmental changes. Daily and weekly variations in spectral noise level were observed clearly in short periods < 1 s, and these are considered to be related to human activities. The seismometers in boreholes showed ~20 dB weaker NLs in the cultural noise band. The NLs of accelerometers at a depth of 30 m were also much lower by 30 dB for long periods > 10 sec. Overall the functioning of the new velocimeter and accelerometer stations was reliable for periods ranging from 0.02~100 s and 0.02~10 s, respectively.
Keywords
Seismic station; Functioning; Noise level; NNM; Cultural noise;
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