Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/1065
AuthorsShinohara, M.* 
Araki, E.* 
Kanazawa, T.* 
Suyehiro, K.* 
Mochizuki, M.* 
Yamada, T.* 
Nakahigashi, K.* 
Kaiho, Y.* 
Fukao, Y.* 
TitleDeep-sea borehole seismological observatories in the western Pacific: temporal variation of seismic noise level and event detection
Issue Date20-Mar-2006
Series/Report no.49 (2-3)
URIhttp://hdl.handle.net/2122/1065
Keywordsdeep-sea borehole observatory
broadband seismometer
seismic noise level
long-term observation
Subject Classification04. Solid Earth::04.06. Seismology::04.06.06. Surveys, measurements, and monitoring 
04. Solid Earth::04.06. Seismology::04.06.10. Instruments and techniques 
AbstractSeismological networks provide critical data for better understanding the dynamics of the Earth; however, a great limitation on existing networks is the uneven distribution of stations. In order to achieve a more uniform distribution of seismic stations, observatories must be constructed in marine areas. The best configuration for oceanic seismic observatories is thought to be placement of seismometers in deep boreholes. Two deep-sea borehole seismological observatories (WP-1 and WP-2) were constructed in the western Pacific and form the initial installations of a 1000 km span network. At present, seismic records of more than 400 total days were retrieved from both the WP-1 and WP-2. Long-term variations in broadband seismic noise spectra (3mHz - 10 Hz) in the western Pacific were revealed from these records, and the data showed that ambient seismic noise levels in borehole observatories are comparable to those of the quietest land seismic stations. In addition, there is little temporal variation of noise levels in periods greater than 10 seconds. Due to this low seismic noise environment, many teleseismic events with magnitudes greater than 5 were recorded. It is confirmed that seismic observation in deep-sea borehole gives the best environment for earthquake observation in marine areas.
Appears in Collections:Annals of Geophysics

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