No. +1 0-10,*++ Technical Research Report, Earthquake Research Institute, the University of Tokyo, No. +1, pp. 0-10,,*++. * ** ** *** * * * Development of a Portable Infrasound Observation System based on the Nano-Resolution Barometric Transducer Takahiko MURAYAMA*, Yuichi IMANISHI**, Shingo WATADA**, Takuma Oi***, Nobuo ARAI*, Makiko IWAKUNI* and Mami NOGAMI* Abstract We report on the development of a low-cost, portable observation system of infrasound. The system consists of the nano-resolution pressure transducer Model 0*** -+0B manufactured by Paroscientific Inc., USA and pressure hoses (flexible polyvinyl chloride product) for reducing wind noise. Field tests were made at Isumi, Japan (), one of the CTBT infrasound monitoring stations. As a result, the, - noise level at the frequency range from **+. to +* Hz was found to be on the order of +* +* Pa when + the wind speed was less than *,. ms. The wind noise reduction system indicated similar performance with the stainless pipe array employed in the CTBT monitoring system even in the strong winds reach- 2 *,*** Systemes, France in the frequency domain confirmed that the two sensors produce almost identical spectra above **,. Hz. The portable system was then installed at the Kurokami-Seto station of Japan Meteorological Agency near Mt. Sakurajima, which is now exploding frequently at the Showa crator. Comparison with the microbarograph Model MB,**/ (successor of MB,***) again confirmed that our system is able to record the infrasonic signals from volcanic explosions in the wide frequency band up to +* Hz. Key words : Infrasound, sensor, digital quartz resonator, CTBT, Volcanic explosion + ing. ms. Comparison with the microbarometer Model MB manufactured by Martec Tekelec,* Hz,*,**** Hz km km Yamamoto,,*++ 2 +3,*++ +*,1 * ** *** * Japan Weather Association, ** Earthquake Research Institute, the University of Tokyo, *** Toho Mercantile co., ltd. 63 +3/. CTBT Comprehen-
64 sive Nuclear Test-Ban Treaty : CTBT CTBT CTBT 0* + *.*+ +* Hz MB,*** **+. Pa, km 0 No. : IS +* -*,**.,**1 CTBT CTBTOPTS CTBTO Preparatory Commission,,*++ MB,*** MB,**/, Ponceau and Bosca,,*+* +** kg Paroscientific Model 0*** -+0B Barometer Paroscientific, Inc.,,**3 2** +, +** hpa +,/**,,*** m + Hz *.***+ Pa,,* Hz *.*+ Pa 0 cm + CTBT infrasound monitoring Network
65 Paroscientific Model. 0*** -+0B Barometer 0*** -+0 B ++. SN 0*** -+0B 02 +.. 1 MHz +1 /3 MHz. IIR +* +** Hz 0*** -+0 B,, Quartz Crystal IIR 0,/ V **,-. Hz 2 Internal Vacuum +* Pa +.. khz - *1. Hz *.**+0 ppm +*** Temperature Sensor 0 cm,* Hz ++ Hz /./ Hz *. +. ppm *.*+. Pa *.*./ ppm *.**./ Pa -/ khz +. jitter 02 + + ppm +, Model 0*** -+0B Barometer, - Model 0*** -+0B Barometer Paroscientific
66. - + *+. Pa +3/* Hedlin et al.,,**- CTBT Inlet WNRS : Wind Noise Reduction System / MB,*** +2 m / 30 +2 m Inlet Ports. Secondary summing manifold
67 +* mm CTBTO Inlet +/ m 0 0 1 +/ mm +* mm,*+* Inlet, 0*** -+0 B RS-,-, C RS-.,, 0*** -+0B 0 CTBT P- P. P- P. P. P. P- OS 1 OS
68 OS GPS GPS C GPS Garmin +/ L Linux ntpd Garmin +/ L GPS +/ P- RS-,-, C +* ms +** Hz NMEA - + PPS TTL + PPS USB Windows OS + PPS FreeBSD Linux +* mm FreeBSD PPS Linux PPS 0*** -+0B :,0-... PPS FreeBSD AC,* Hz UPS +** Hz OS Linux Linux PPS LinuxPPS LinuxPPS Garmin +/ L ntpd UPS OS GPS + mm ntpd jitter +* Garmin +/ L - + PPS OS + Windows Linux OS 0*** -+0B OS MB,*** Imanishi,,**+ Linux
69 /*,**3 3,3,**3 ++ +1 /* +** CTBT IS -* : H+ 0*** -+0B 2, 0*** -+0 B SN+++,.. SN -/ +2,1. 3, N, +.* +2.3./. E, ELEV,* m ++/+,3 0*** -+0B 0*** -+0B - 3,. +* +* m *.*- *., Hz 1, +* Pa Hz, -Hz - Hz Linux - *,. Hz -, - +* +* Pa ntp GPS PPS Pulse Per WNRS Second FreeBSD 0*** -+0 B SN++/+,3 SN++/+,* 0*** -+0 B /*. m 2*. m ++ //. Hz *-. Hz MB,***,* Hz +* m 0*** -+0 B.,* m / m. *,/. Hz 0*** -+0 B MB,*** *., m 0*** -+0B MB,*** 0*** -+0B 2 +, +*
70 3, *.*+ +* Hz MB,*** 0*** -+0B
71 +* +, 0*** -+0 B MB,*** +- 0 ++ /*. m 2*. m WNRS 0,* m - 0*** -+0B MB,**/,*+* -,3,*++,, +* MB,*** CTBT : D +- +/ +0 +0 -+ -..,/ N, +-*.,... E, ELEV 3,. 2 m + 0*** -+0 B SN++/+,* MB,**/ +. -
72 +* Hz 0*** -+0B,, Hz +** Hz 0*** -+0B MB,*** -2 GPS. +** +1 a b c a b c +. -0Hz +/
73 +0 +0B b *+. +* Hz + 0*** -+0 B MB,**/ 0*** -+0 B MB,**/ c *. + +* Hz * 0*** -+0B MB,**/ *. + +* Hz 0*** -+0B MB,**/ 0*** -+0 B +** Hz MB,**/,** Hz ACO MB,**/ +** Hz,*++ +* -,* ++,,*.2 MB,**/,,* 0*** -+0B, +3 +/ msec *./- +2 a 0*** -+0B +* Hz b c b MB,**/ 0*** -+0 BcMB,**/ 0*** -
74 +1 *.*+ +* Hz MB,*** Paroscientific MB,**/ 0*** -+0 B *.*- *., Hz Model 0*** -+0 B Barometer +* Pa Hz 1, 0*** - +0B CTBT CTBT MB,*** MB,**/ 0*** -+0 B MB,*** MB,**/ 2** +, +** hpa 0*** -+0 B MB,*** MB,**/
75 +2 0*** -+0 B MB,**/ : GPS 0*** -+0B 0*** - +0B
76 +3 0*** -+0B 233 3*,.,*+* CTBTO 3.13/*.,*++ ++3+ ++3.. CTBTO Preparatory Commission, http : //tfcs.ctbto.org/download / attachments/.2.31--/ Portablearray. pdf? version, & modificationdate +-*./3-+-0***,,*++. Hedlin, M.A.H., Alcoverro, B. and D Spain, G.,,**-, Evaluation of rosette infrasonic noise reducing spatial filters, J. Acoust. Soc. Am ++., +2*1 +2,*. Imanishi, Y.,,**+, Development of a high-rate and high-resolution data acquisition system based on a real-time operating system, J. Geod. Soc. Japan,.1, /, /1. Paroscientific Inc., http : //www.paroscientific.com/nano-resolution. pdf,,**3. Ponceau, D., Bosca, L.,,*+*, Infrasound Monitoring for Atmospheric Studies, Springer, ++3 +-+. Yamamoto, R., +3/., Bulletin of the Institute for Chemical Research, Kyoto University, Supplementary Issue November +3/., +,* --.,**1