HR: 0800h
AN: S31A-0283    [Abstracts]
TI: On the Generation of Love waves in the Microseisms - Analysis of Typhoon Generated Microseisms
AU: * Kawakami, Y
EM: kawa821@eri.u-tokyo.ac.jp
AF: Earthquake Research Instiute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032 Japan
AU: Nishida, K
EM: knishida@eri.u-tokyo.ac.jp
AF: Earthquake Research Instiute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032 Japan
AU: Kawakatsu, H
EM: hitosi@eri.u-tokyo.ac.jp
AF: Earthquake Research Instiute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-0032 Japan
AU: Obara, K
EM: obara@bosai.go.jp
AF: National Research Institute for Earth Science and Disaster Prevention, 3-1 Tennoda, Tsukuba, 305-0006 Japan
AB: We have conducted semblance analyses of the long-period (5-20sec) seismic noise wavefield utilizing records of the Hi-net tiltmeter network which is operated by the National Research Institute for Earth Science and Disaster Prevention. The Hi-net tiltmeter network consists of about 680 tiltmeters buried in deep boreholes, and can be used as a network of horizontal broadband seismometers (accelerometers). The initial array analysis using regional sub-networks for radial and transverse components reveals presence of both Rayleigh and Love waves in the microseisms with the approximate slowness of 0.32sec/km and 0.29sec/km, respectively. To our surprise, the energy partition of the two surface waves turn out to be almost equal for both the primary and the secondary microseisms. To further delineate the origin of these microseisms, especially the large amplitude Love waves, we analyze typhoon-generated microseisms to map out the source region of the strong microseismic energy. We use the whole network data to map the source area of two typhoons that stuck the Japanese islands in 2004 (typhoon #6 and #10). For both events, the areas of the strongest energy are located in small areas near the coast of the Honshu island when typhoons are close to the island. Also the strongest source areas of both Rayleigh and Love waves are located in common places. This indicates that the sources of microseismic Rayleigh and Love waves share the same origin, and the microseismic Love waves are not due to the secondary effects such as scattering of microseismic Rayleigh waves due to the lateral heterogeneity of the shallow part of the Earth.
DE: 7255 Surface waves and free oscillations
DE: 7270 Tomography (6982, 8180)
SC: Seismology [S]
MN: Fall Meeting 2005