1. Atmospheric Pressure Change Associated with the 2003 Tokachi-Oki Earthquake Shingo Watada, Takashi Kunugi, Keinji Hiarata, Hiroko Sugioka, Kiwamu Nishida, Shoji Sekiguchi, Jun Oikawa, Yoshinobu Tsuji, Hiroo Kanamori

2. microbarogram2003/09/26 ２４ hour 1000sec JIZODO STS1 vault

4. Software configuration Microbarograph recording and telemetry systems Hardware configuration GPS antenna Sensor Control PC

5. On-line board PC based system SGN (Yamanashi, Japan) Air battery Portable sensor Board PC Microbarograph sensor Off-line recording system

6. Ground vertical velocity Filtered atmospheric pressure 3.2km/sec atmosphere Ground

8. atmosphere Ground for homogeneous fluid

9. Observational transfer function

10. Mechanical sensitivty check by shake table

11. Theoretical transfer function of long-period atmospheric waves. atmosphere Ground for homogeneous fluid High frequency asymptote for propagating acoustic waves

12. Conclustion The atmospheric pressure change associted with the 2003 Tokachi-Oki earthquake are observed at the co-located site of broadband seismometers. The origin of atmospheric pressure change is the Rayleigh waves passing at the site. The observational transfer functions, both phase and amplitude, are constructed and compared with the theoretical transfer functions and found consistent up to 50 sec.