[M-TT43_1PM2] Brand-new scope of coupling geophysics being established by infrasound and associated waves

[MTT43-P02_PG] Improvement and evaluation of optical-type infrasound sensor for multi-site observation

3-min talk in an oral session

*Kousuke IKEHARA¹, Masa-yuki YAMAMOTO¹, Yoshihiro KAKINAMI¹, Yoshiaki ISHIHARA² (1.Kochi University of Technology, 2.JAXA Space Exploration Center, Japan Aerospace Exploration Agency)

Keywords:infrasound, multi-site observation, sensor development, optics, measurement, low-cost

Infrasound is applicable for remote-sensing methods for detecting geophysical phenomena in the atmosphere. There have been developed and used many types of infrasound sensors, however, typically used infrasound sensors are almost developed by foreign countries, resulting high cost situation in Japan. If we can develop low cost infrasound sensors, multi-site arrayed observation will be realized in near future.Recently, infrasound signal generated by tsunami was clearly detected by many CTBTO infrasound stations (Arai et al., 2011), suggesting a new era for establishing a dense infrasound sensor network in every prefecture of Japan for preventing or reducing catastrophic disasters. Because the nature of pressure waves with large wavelength, amplitude of infrasound generated by tsunami might be proportional to the size of the disasters. Combination with sensor networks of seismometers on ground and ocean floor, GPS-buoy type wave recorders, and water manometers on ocean floor, establishing a dense network of infrasound sensors with arrayed configuration is desired.Since 2006, we have been developing new sensing method of infrasound by using piezo film and PSD (Position Sensitive Detectors), achieving frequency range between 0.001 Hz and 10 Hz as well as minimum pressure level of 0.01 Pa (Yamamoto and Ishihara, 2009). In 2013, we tried downsizing the PSD type infrasound sensor developed in 2008 into a size of 0.15 m x 0.15 m x 0.25 m height with calibrating it by using space chamber (0.8 m length x 0.58 m diameter) as an accurate volume pressure reservoir (Manabe et al., 2013). Here, we improved the PSD optical-type infrasound sensor by using 3D printer technology to make many tiny parts designed with 3D CAD software.By pushing and pulling a small amount of air by a small syringe, calibrating pressure waves with extremely weak amplitude (10 Pa to 0.01 Pa) can be generated in the space chamber, precise measurement of artificially generated infrasonic signals could be realized. The waves were measured by both of the developed PSD sensor and Chaparral Model-2.5 infrasound sensor at the same time. Comparison with output signals by two types of sensors, the downsized PSD type infrasound sensor was carefully studied. In this paper, we will introduce the new design and obtained calibrating datasets.