Systematic research on low-frequency tremor, "very" low-frequency earthquake and slow slip event

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 16340131
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Solid earth and planetary physics
• Research Institution: Hiroshima University
• Principal Investigator: SUDA Naoki Hiroshima University, Graduate School of Science, Associate Professor, 大学院理学研究科, 助教授 (10222069)
• Co-Investigator(Kenkyū-buntansha): ISHIHARA Yasushi JAMSTEC, IFREE, Technical Researcher, 固体地球統合フロンティア研究システム, 技術研究員 (40232334)
• Project Period (FY): 2004 – 2006
• Keywords: low-frequency tremor / real-time / ATMOS / automatic detection / hypocenter determination / Bungo channel / very" low-frequency earthquake / broadband seismometer

Research Abstract

(1) To monitor activity of low-frequency tremors occur in southwest Japan in real-time, we have developed an automatic tremor monitoring system, ATMOS. The system uses real-time seismic data distributed on broadband network, and analyzes to examine whether tremor occur or not on every two minute by using a method based on a numerical statistical hypothesis test. If tremor is detected, then its hypocenter is determined. The system also creates images showing monitored results, and they are automatically opened to the public with WWW.
(2) To investigate activity of low-frequency tremors in the Bungo channel region, we have installed a broadband seismometer at Hiburijima Island, which locates in the Bungo channel about 25 km away from Uwajima city, Ehime prefecture. The sensor installed is Streckeisen STS-2, and the data logger is QUATERRA Q330+PB14. Seismic data is downloaded by way of Internet using the ISDN telephone line. Analyses of seismograms have shown that the noise level at the Hiburijima station in the tremor frequency band between 2 and 20 Hz is lower than those at seismic stations in Kyushu Island near the Bungo channel. The installation of seismometer in Hiburijima island has allowed us to observe low-frequency tremors in Bungo channel region more precise than before.