Kenji HIRATA Hiroko SUGIOKA Itaru FUJISAWA Takeshi KATAYAMA. Yuka KAIHO Kenji HISHIKI. Shizuo KASHIWABARA

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1 STS- Hz m/s /Hz HzSTS-. Hz m/s p-p mgal p-p.. Hz m/s p-p.. mgal p-p Hz m/s p-p.. mgalp-p.. Hz db Hz db On characteristics of inherent sensor noise of ocean bottom seismometers attached on the real-time seafloor geophysical observatory off Kushiro-Tokachi - A calibration test at the JMA matsuhiro seismological observatory - Kenji HIRATA Hiroko SUGIOKA Itaru FUJISAWA Takeshi KATAYAMA Yuka KAIHO Kenji HISHIKI Shizuo KASHIWABARA Ocean bottom seismometers OBSs attached on the cable-connected geophysical observatory off Kushiro - Tokachi, Hokkaido, Japan were calibrated by comparing with IRIS STS- at JMA Matsushiro seismological observatory MAT before the geophysical observatory was deployed in July. Power spectral density PSD from the OBSs showed a constant level of m/s /Hz in a frequency range higher than Hz and a gradual increasing in a frequency range lower than Hz. PSD from IRIS STS- at MAT showed a typical spectral structure of background seismic Japan Marine Science and Technology Center NEC Ocean Engineering, Ltd. JMA matsushiro seismological observatory

The total-system noise appeared as random noise time series with an RMS amplitude of m/s p-p. This was considered to be generated from a sensor pick based on a noise evaluation test.

2 noise, and was lowered than that of the OBSs in a frequency range between. Hz and Hz. By comparing PSD from the OBSs with that from STS-, it was concluded that a total-system noise level of the OBSs is so higher than the background seismic noise level at MAT. The total-system noise appeared as random noise time series with an RMS amplitude of m/s p-p. This was considered to be generated from a sensor pick based on a noise evaluation test. The RMS amplitude of the inherent sensor noise was m/s p-p between. and. Hz and m/s p-p between. and Hz. Therefore, total dynamic range obtained from high- and low-gain channels of our OBSs is estimated to be db for. to. Hz, and db for to Hz. Keywords : sensor noise, dynamic range, ocean bottom seismometer, cable-connected geophysical observatory off Kushiro Hirata et al., JA- IIIA Kanazawa and Hasegawa, Incorporated Photo An ocean bottom seismometer attached on the geophysical observatory off Kushiro, Hokkaido, Japan. Three orthogonal axes indicate directions of +x-, +y-, and +z-components. KOBS KOBS KOBS Fig. Positions green circles of three ocean bottom seismometers, KOBS, KOBS, and KOBS, attached on the geophysical observatory off Kushiro. Red line indicates a cable route.

Research Institutions for Seismology IRIS STS-.s KOBSIRIS STS-m KOBS KOBS,, +X +Y +Z DC +X +Y+Z KOBS KOBS KOBS m JA- IIIA. ma/g Rs =. k V/G Hz. Hz V/G bit A/D Crystal Semi-conductor CSCS khzhz Hz A/D.

3 Research Institutions for Seismology IRIS STS-.s KOBSIRIS STS-m KOBS KOBS,, +X +Y +Z DC +X +Y+Z KOBS KOBS KOBS m JA- IIIA. ma/g Rs =. k V/G Hz. Hz V/G bit A/D Crystal Semi-conductor CSCS khzhz Hz A/D. V/G bit khz FFT JA Photo Three ocean bottom seismometers set on the JMA Matsushiro seismological observatory for a calibration test. The three were installed off Kushiro in July, after this test. STS- Fig. Arrangement of the three OBSs and IRIS STS- in the JMA Matsushiro seismological observatory MAT. Fig. A block diagram of the observation system of the KOBSs.

4 KOBS STS- m/s /Hz KOBS STS- fold STS- KOBS STS-. Hz microseism. Hz m/s /Hz Hz IRIS web STS- ambient seismic noise background seismic noise Hz Hz STS- KOBSSTS- Hz m/s /Hz Hz KOBS STS- STS- KOBSKOBS Fig. Comparison power spectral density PSD from high-gain channel of KOBS with that from IRIS STS- at MAT. While PSD from IRIS STS- shows a typical structure of background seismic noise at MAT, PSD from KOBS does not show the similar structure. PSD from KOBS is larger at least times than PSD from IRIS STS- between. Hz and Hz. A system noise of KOBS is considered to be larger than the typical background noise at MAT. KOBSXYZ RMSm/s RMS. m/s. mgal Fig. A time series from KOBS high-gain channel at MAT. A numeral attached at the upper-right corner of each trace indicates RMS half-amplitude in m/s. A system noise appears as a random noise with an RMS half-amplitudes of. m/s. mgal. top ; X-component, middle ; Y-component, bottom ; Z-component.

ars b Rs Fig. a Block diagram of the observation system for evaluating the system noise in a case where sensor outputs exist. External resistivity Rs is allowed to change to an arbitrary value.

5 ars b Rs Fig. a Block diagram of the observation system for evaluating the system noise in a case where sensor outputs exist. External resistivity Rs is allowed to change to an arbitrary value. b Block diagram of the observation system for evaluating a circuit noise. External resistivity Rs is allowed to change to an arbitrary value. a Rs Rs Fig. System noise time series upper and their amplitude spectra lower obtained by using the observation system in Fig. a when external resistivity Rs is changed. System noise level increases with Rs value.

6 . Hz m/s /Hz STS- KOBS STS- KOBS RMS. m/s. mgal KOBS KOBS.. a Rs Rs Rs a Rs FFT Rs b Hz dbv dbv / /,.. KOBS KOBS.Hz Hirata et al., Hz b Fig. Circuit noise time series upper and their amplitude spectra lower obtained by using the observation system in Fig. a. Comparing by the corresponding time series and amplitude spectra in Figs and, the system noise level is to, times as large as the circuit noise level. Hz Hz

7 KOBS KOBS Fig. Comparison between PSD from high-gain channel of KOBS actually installed off Kushiro, Hokkaido, Japan and that of the inherent sensor noise. JA- IIIA JA- A JA- IIIA JA- A m/s mgal JA- A.. Hz m/s. mgal JA- A KOBS.. Hz a RMS.. m/s.. mgal b Hz KOBSa.. Hz b Hz RMSm/s Fig. Filtered time series of the inherent sensor noise from KOBS high-gain channels at MAT. a A band-pass filter with corner frequencies of. Hz and. Hz is applied. b A band-pass filter with corner frequencies of. Hz and Hz is applied. A numeral attached at the upper-right corner of each trace indicates RMS half-amplitude in m/s.

8 RMS m/s.. mgal M Hz M m/s.. mgal.. Hz Hz m/s p-p.. mgalp-p JA- IIIA JA- IIIA. m/s gal m/s gal Hirata et al., Hz db db.. Hz db db STS-STS- Hz JA- IIIA HNM LNM Paterson Fig. Comparison between PSD of the inherent sensor noise of JA- IIIA and those of other seismic sensors. PSDs of other seismic sensors are based on catalog data. Microseism actually obtained with JA- IIIA off Kushiro and background seismic noise models, HNM and LNM Paterson, are also plotted.

9 .. Hz m/s p-p.. mgal p-p Hz m/s p-p.. mgalp-p.. Hz db Hz db NEC Hirata K., M.Aoyagi, H. Mikada, K.Kawaguchi, Y.Kaiho, R.Iwase, S.Morita, I. Fujisawa, H. Sugioka, K. Mitsuzawa, K. Suyehiro, H. Kinoshita: Real-time geophysical measurements on the deep seafloor using submarine cable in the southern Kurile subduction zone, submitted to IEEE J. Ocea Engineering. Kanazawa T. and A. Hasegawa: Ocean-bottom observatory for earthquake and tsunami off Sanriku, Northeastern Japan using submarine cable, Proc. International Workshop on Scientific Use of Submarine Cables, Paterson, J.: Observations and Modeling of Seismic Background Noise, USGS Open File Report, -. : - : -.

NFPA (2012). In a high-rise building, stairwell pressurization systems typically utilize multiple fans distributed over the height of the stair, a duc

NFPA (2012). In a high-rise building, stairwell pressurization systems typically utilize multiple fans distributed over the height of the stair, a duc Numerical and Experimental Investigation of Pressurization System in a High-Rise Building with Stairwell Compartmentation B. Hepguzel 1,* 1 Mechanical Engineering Faculty, Istanbul Technical University,