Japanese University Joint Dense Seismic Observation on and around Fuji Volcano (September,, April,/)

Μέγεθος: px

Εμφάνιση ξεκινά από τη σελίδα:

Download "Japanese University Joint Dense Seismic Observation on and around Fuji Volcano (September,**, April,**/)"

Βαρβάρα Κακριδής
6 χρόνια πριν
Προβολές:

1 Bull. Earthq. Res. Inst. Univ. Tokyo Vol. 2,,**1 pp. +3/,*1,**, 3,**/ * ,,,, / / / , -. / Japanese University Joint Dense Seismic Observation on and around Fuji Volcano (September,**, April,**/) Hidefumi Watanabe *, Haruhisa Nakamichi, Takao Ohminato, Tsuneomi Kagiyama, Jun Oikawa, Yosuke Aoki, Hiroshi Tsuji, Etsurou Koyama, Noboru Osada, Michinori Hagiwara, Toyotarou Takeda, Masakatsu Kobayashi, Hiromitsu Oshima, Hi ,,,, - roshi Aoyama, Tokumitsu Maekawa, Atsuo Suzuki, Satoshi Tanaka, Takeshi Nishimura, Kouichi Nita, Jun Yamazaki, Takashi Okuda, Mamoru Yamada, Takahiro Okura, Yasuaki Sudo, Shin Yoshikawa, Masato Iguchi, Hiroshi Shimizu, / / / 0 1 Kenji Uehira, Ken Matsushima, Hiroshi Yakiwara Earthquake Research Institute, University of Tokyo, +, Graduate School of Science, Hokkaido -. University, Graduate School of Science, Tohoku University, Graduate School of Science, Nagoya / 0 University, Graduate School of Science, Kyoto University, Disaster Prevention Research Institute, Kyoto University, Graduate School of Science, Kyushu University, Faculty of 1 2 Science, Kagoshima University and Shuichiro Hirano Abstract A joint dense seismic observation experiment was conducted during the period of September,**, April,**/ in cooperation of researchers of national universities under the national project for prediction of volcanic eruption. Major objectives include seismic exploration of the subsurface structure of Fuji volcano and surrounding area as well as array observation of deep low frequency earthquakes, the activity of which increased in,***,**+ beneath the volcano. We installed,2 seismographs temporarily on and around Fuji volcano and the data was transmitted to the Volcano Research Center (VRC), Earthquake Research Institute by satellite, radio and cable telemetry systems. We further collected seismic data of permanent stations around Fuji volcano operated by related research institutions. All the data was collected and picked at VRC. In this initial report we describe the brief outline of the joint experiment, and summarize the preliminary results of analyses on the seismic velocity structure of Fuji volcano and wave characteristics of a low frequency earthquake, which occurred on ++ September,**-. Key words: Mt. Fuji, array observation, velocity structure, low frequency earthquake, eruption prediction * watanabe@eri.u-tokyo.ac.jp ++- **-,

2 +,**+ +32* - +* +, - Kanjo et al., +32. ; +32. ; +320 ; +33-,***,***,**+,**+ a, b; Ukawa,,** ,* km Nakamichi et al.,,**-,**,,,**, - / Ta- ble +,**, 1 2 3,**+,**, Hi-net Hi-net,*** -* km +** km Hi-net +*,* km +,,***,**+ -,

3 Table +. General outline and agreement on the joint dense seismic observation experiment on and around Fuji volcano.,,+,**+,**, +* 0,**, 3 +*. +*,* km /,**- 0 km, Table,,**,,** ,**.,**, - 197

The various symbols in the figure denote seismic stations operated by several institutions as indicated in legend.

4 Table,. A list of temporal seismic stations on and around Fuji volcano. Fig. +. Location map of the dense seismic observation network around Fuji volcano. The various symbols in the figure denote seismic stations operated by several institutions as indicated in legend. Solid symbols indicate the temporal seismic stations operated during the present dense observation experiment. Gray stars are shot points of the seismic exploration experiment in,** Fig. + / +* km,2,**

5 ,,,**. CMG--T - Güralp +** 0 Trillium Nano- Nanometrics Lynx Cyguns metrics.* 1 L. - D Mark Prod- Trident,. D ucts Sercel + +/ AD - +-, db Lynx +., db Trident DC++ +0V -* W CMG-- T +** V Trillium L.- - D AC-DC +, V Fig., a /0* W L. -D Trillium 0.* Ah./ cm CMG--T 0* cm. 2* W 2* Ah LS-1*** XT RM-** LS-1*** XT AD Fig.,. Photos of di# erent types of temporal seismic stations using VSAT telemetry with solar battery (a), radio telemetry with solar battery (b) and wire telemetry with AC power (c). 199

6 Fig. -,- + P S AC P S,**, +*,**/ - +,**0. Fig., a b c P S +, DAT CD- ROM CD-ROM -,**-. +* Fig. -. Schematic diagram showing data telemetry and processing system for the present seismic observation. 200

; pocenter distribution of earthquakes during the period of +332 +333 used for the checkerboard tests +320 (a), and the results for grid

7 Fig... Hypocenter distribution of earthquakes that occurred around Fuji volcano during the period, April to October,**-. Fig.. Fig. /. The results of checkerboard tests for the seismic velocity tomography around Fuji volcano. Hy- Huchon and Kitazato, +32. ; pocenter distribution of earthquakes during the period of used for the checkerboard tests +320 (a), and the results for grid spacing of / km (b) and. km (c). Fig. / b c / km,. km +,,* km. km..+.,, +00,**, +*,**. + Fig. / a, Fig. / a + P +*, PS +/ -1 - P S RMS *.,,2 201

8 Fig. /. (continued) 202

9 Bayesian approach kms -,**,; Onizawa et al,,**, / km, +* km, +/ km,,* km / km,/ km -/ km +* km Fig. 0 * / km - Double- Tanaka et al.,,**, Yama- di# erence tomography method Zhang and Thurber, waki et al.,,**. +*,* km P /. 20 kms,**- Fig. 0 +* +/ Nakamichi et al.,,**1 km / km / km P 1 Fig. 0. The preliminary results of seismic velocity tomography around Fuji volcano. 203

Vertical component velocity seismograms of the low frequency earthquake, which occurred beneath Fuji volcano at,* : -. JST on ++ September,**-.

10 /,***,**+,**, +*,**. -,**- 3 ++,* Fig. 1 / Hz Fig. ++ HSO OIS MMS FUJ MTS +.., km HSO Fig. 2 *.. Fig. 1. Vertical component velocity seismograms of the low frequency earthquake, which occurred beneath Fuji volcano at,* : -. JST on ++ September,**-. The left side shows unfiltered seismograms and the right side those obtained after / Hz low-pass filtering. Each trace is normalized by its maximum amplitude. Location of seismic stations is shown in the Figure ++. Fig. 2. Vertical component velocity seismogram and its running spectra observed at the station HSO for the low frequency earthquake, which occurred at,* : -. JST on ++ September,**-. 204

B *.. Hz Fig. ++ + *.. Hz,* -* P *.. Hz Fig. 3.

Predominant directions of particle motion observed around Mt. Fuji for the *.

Band passed seismograms of the vertical component seismogram observed at HSO (Fig. 2). 0 Note that the *.

11 B *.. Hz Fig *.. Hz,* -* P *.. Hz Fig. 3. Spectral amplitude of the vertical component seismogram observed at HSO (Fig. 2). Fig. ++. Predominant directions of particle motion observed around Mt. Fuji for the *.. Hz component of the low frequency earthquake at,* : -. JST on ++ September,**-. Fig. +*. Band passed seismograms of the vertical component seismogram observed at HSO (Fig. 2). 0 Note that the *.. Hz component started a few seconds +33* later (arrow B) after the initial arrival of P phase (arrow A). Iidaka et al., +33* ; +33- Hz *2. Hz Fig. 3 *.. Hz *2. Hz *.. Hz, *2. Hz *3. Hz Fig. +* *2. Hz.* *.. Hz +/,* *.. Hz P A 205

12 Tectonophysics, +13, -,+ -, Lees and 2 /3+ /31 Ukawa, +33, Kanjo, K., I. Karakama and R.S. Matsuura, +32., Seismic MT, Aizawa et activities of Mt. Fuji region detected by continuous observation al.,,**.,* km of micro-earthquakes, J. Phys. Earth, -,, ,* km Lees, J.M. and M. Ukawa, +33,, The South Fossa Magna, Japan, revealed by high-resolution P- and S-wave travel time tomography, Tectonophysics,,*2, ,** Nakamichi, H., S. Tanaka and H. Hamaguchi,,**,, Fine S wave velocity structure beneath Iwate volcano, northeastern Japan, as derived from receiver functions and travel times, J. Volcanol. Geotherm. Res., ++0,,-/,//. Nakamichi, H., H. Hamaguchi, S, Tanaka, S. Ueki, T. Nishimura and A. Hasegawa,,**-, Source mechanisms of deep and intermediate-depth low-frequency earthquakes beneath Iwate volcano, northeastern Japan, Geophys. J. Int., +/., 2++ 2,2. Nakamichi, H., H. Watanabe and T. Ohminato,,**1, Threedimensional velocity structures of Mount Fuji and the,**, South Fossa Magna, central Japan, J. Geophys. Res., ++,,,**+,**- B *--+*, doi: +*. +*,3 /,**/ JB **.+0+.,**..2,-,0. +.,**, -.1.3/ /*0. Onizawa, S., H. Mikada, H. Watanabe and S. Sakashita,,**,, A method for simultaneous velocity and density inversion and its application to exploration of subsurface structure beneath Izu-Oshima volcano, Japan, Earth Planets Space, /., 2* Hi-net +32, +* , 0+ /210+-.,***,, /+0 /,-. Tanaka, S., H. Hamaguchi, T. Nishimura, T. Yamawaki, S. Ueki, H. Nakamichi, T. Tsutsui, H. Miyamachi, N. Matsuwo, J. Oikawa, T. Ohminato, K. Miyaoka, S. Onizawa, T. Mori and K. Aizawa,,**,, Three-dimensional P-wave velocity structure of Iwate volcano, Japan from active seismic survey, Geophys. Res. Lett.,,3 ( +* ), doi: +*. +*,3/,**, GL * Aizawa, K., R. Yoshimura and N. Oshiman,,**., Splitting of +33- the Philippine Sea Plate and a magma chamber beneath Mt. Fuji, Geophys. Res. Lett, -+, L *30*-, doi: +*. +*,3 /,**. SP.0 +* GL * Huchon, P. and H. Kitazato,, Collision of the Izu block with central Japan during the quaternary and geological evolution of the Ashigara area, Tectonophysics, ++*, -1 +, /30..,*+,+*. Kobayasi, T. Haneda and S. Hashimoto, +33*, The upper,***,, /-/ /-3,**+ a, * ern Kanto region estimated from S-P-converted wave,,**+ b 206

13 P-wave velocity structure of Bandai volcano in north- Ukawa, M.,,**-, Activity of Fuji volcano, Reports on vol- eastern Japan inferred from active seismic survey, J. canic activities and volcanological studies in Japan for Volcanol. Geotherm. Res., +-2,,01,2,. the period from +333 to,**,, +2,,. Zhang, H. and C. H. Thurber,,**-, Double-di# erence tomography,**. - : the method and its application to the Hayward fault, California, Bull. Seism. Soc. Amer., 3-, +21/ Yamawaki, T., S. Tanaka, S. Ueki, H. Hamaguchi, H. Nakamichi, T. Nishimura and et al.,,**., Three-dimensional Received April 3,,**1 Accepted August -,,**1 207

Σχετικά έγγραφα

Focal Mechanism Solutions of Micro- and Small Earthquakes Occurred in the Western Kanagawa Area Situated in the Izu Collision Zone

Bull Earthq Res Inst Univ Tokyo Vol 2,**3 pp,33-*/ * +, + + + + +, + + Focal Mechanism Solutions of Micro- and Small Earthquakes Occurred in the Western Kanagawa Area Situated in the Izu Collision Zone