HR: 1340h
AN: S23A-1105    [Abstracts]
TI: Swell Propagation Along Japan Coast Detected by Associated Microseisms Observed With Seafloor Cabled Observatories
AU: * Iwase, R
EM: iwaser@jamstec.go.jp
AF: JAMSTEC, 2-15 Natsushima-cho, Yokosuka, Kanagawa, 237-0061, Japan
AU: Kikuchi, T
EM: ads01881@nifty.com
AF: National Defense Academy, 1-10-20 Hashirimizu, Yokosuka, Kanagawa, 239-8686, Japan
AU: Mizutani, K
EM: mizutani@esys.tsukuba.ac.jp
AF: University of Tsukuba, 1-1-1 Tennodai, Tsukuba City, Ibraki, 305-8573,
AB: A prominent case of swell propagation along Japan coast which was detected through the observation of microseisms with deep seafloor cabled observatories is presented. In July 2001, a large swell which was generated by No. 4 typhoon attacked Japan coast, although the typhoon itself moved westward in the ocean more than 2000 km south of southern coast of Japan and it did not exert direct influence on weather over Japan. Microseisms with a spectral peak at 0.13 Hz which were associated with the arrival of the swell were observed by three seafloor cabled observatories; off Muroto Cape in Kochi Prefecture (western part of Japan), off Hatsushima Island in Sagami Bay (central part of Japan) and off Kushiro in Hokkaido (northern part of Japan). Time difference of the appearance of the microseism is roughly equivalent to the propagation time of deep water wave, with the same time period of a significant wave observed by a wave height meter at the coast, over the distance corresponding latitude difference between the observatories. In other words, the swell propagated from south and reached north to Hokkaido. The peak frequency 0.13 Hz of the microseism corresponds to double frequency of the significant wave frequency observed at the coast. In addition, considering microseisms observed with seismometers on land, the microseisms associated with the swell appeared to be generated at southern coast of both Honshu and Hokkaido where the coastline lies almost perpendicular to the propagation direction of the swell, but did not at eastern coast of Honshu where the coastline is almost parallel. This suggests topographical influence on the generation of microseisms by swells.
UR: http://www.jamstec.go.jp
DE: 3050 Ocean observatories and experiments
DE: 4560 Surface waves and tides (1222)
DE: 7299 General or miscellaneous
SC: Seismology [S]
MN: 2007 Fall Meeting