Mechanical sensitivity of pressure sensors and a correlation between seismic and infrasound signals
Abstract
Mechanical sensitivity of two pressure sensors MB2000 and Chaparral5, widely used in the International Monitoring System (IMS) infrasound network, has been examined using shake table. Both sensors appeared to be sensitive to mechanical vibrations with different level and shape of the mechanical response. Mechanical sensitivity of both sensors to ground motion allows estimating the acceleration amplitudes generated by different size of earthquakes or explosions, which could potentially induce the output signal from microbarometers above the acoustic background. The work results contain the graph of expected level of microbarometer output p-p amplitudes for different earthquake magnitudes and epicentral distances. In addition to mechanical sensitivity the analysis of the real data shows second possible mechanism of the correlation between pressure and seismic signals in the output of co-located pressure and seismic sensors. The near- simultaneous perturbations seen in both seismic and pressure channels suggest that the locally-produced pressure waves seen in the infrasound record are caused by vertical ground motion (the "piston" effect). The amplitude coupling of a wave between the solid earth and the atmosphere has been estimated as Äp/í=Ñc where Äp is the atmospheric pressure change caused by a ground velocity í; the product Ñc is the acoustic impedance of the lower atmosphere with density Ñ and sound velocity c. As the conclusion it was assumed that in the frequency range f<1.5 Hzthe "piston effect" makes the main contribution, whereas for f>1.5 Hz prevails mechanical sensitivity of MB2000. The data analysis has been based on the simultaneous observations at several co-locates IMS stations for Altay earthquake on September 27, 2003, the earthquake in Japan on January 19, 2005, Indonesian earthquake on October 10, 2002 and disruptive event in Sumatra on December 26, 2004.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2006
- Bibcode:
- 2006AGUSM.S31A..06S
- Keywords:
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- 7212 Earthquake ground motions and engineering seismology;
- 7219 Seismic monitoring and test-ban treaty verification;
- 7294 Seismic instruments and networks (0935;
- 3025);
- 0394 Instruments and techniques