Two-ship Seismic Reflection Profiling Across the Source Area of the,**1 Noto Hanto Earthquake, Central Japan

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1 Bull. Earthq. Res. Inst. Univ. Tokyo Vol. 2,,**1 pp.,1/,33,**1 * +, - +,, + -, Two-ship Seismic Reflection Profiling Across the Source Area of the,**1 Noto Hanto Earthquake, Central Japan Hiroshi Sato *, Susumu Abe, Hideo Saito, Naoko Kato, Tanio Ito +, - +,, + -, Earthquake Research Institute, the University of Tokyo JGI. Inc. Graduate School of Science, Chiba University and Taku Kawanaka Abstract In,**1, the northwestern part of the Noto peninsula, central Japan, was struck by damaging earthquakes of M JMA 03.. To correlate seismogenic source faults with geologic structure we conducted seismic reflection profiling of the focal areas. We used two vessels: a gun-ship with a +,/** cu. inch air-gun and a cable-ship with a +.,-km-long, streamer cable and a.2* cu. inch air-gun. Common mid-point seismic reflection data was acquired by total +/* km-long seismic lines. The obtained seismic sections portray faults, that displaced the shallowest part of the reflectors. A deeper extension of the active fault was traced down to. km in depth on the seismic section. The deeper extension of the imaged fault accords well with the linear distribution of the hypocenters of aftershocks, providing direct evidence of fault reactivation at depth. Seismic sections suggest the three tectonic phases; the early Miocene rifting, late Miocene, and Late Pliocene to Quaternary shortening deformation. The,**1 Noto Hanto earthquake was generated by reverse and strike-slip faulting of Miocene normal fault under a compressional stress regime with a WNW-ESE trending P-axis. The ruptured fault segment is strongly controlled by transfer faults, which was formed during the rifting. Key words:,**1 Noto Hanto earthquake, two-ship seismic reflection profiling, earthquake source fault, central Japan + e.g. Sato et al., +332; Allmendinger and Shaw,,***; Kato et al.,,**.,,**0,**1 -,/ M 0. 3,**+,**/;,**1,**2; Sakai et al.,,**2; Yamada et al.,,**2 * **-, JMA,**1 ; Kato et al.,

2 ,**1 3 Fig. +,* km,,.** m, 2+* cu. inch Fig. + BIRPS British Institution s Reflection Profiling Syndicate +31- Singh, et al., +332 Tsuru et al.,,**/,**1 +32/ +320,,**/,**1 12 +/*,** m,**1,** Fig. +. Location of the seismic lines of the west of Noto Peninsula seismic survey. 276

3 ,**1 A Kano et al.,,**, /*. km,**1 3. 3,* 1,**1,* Ma -, +33, +** m,**1 Kano et al.,,**,;,**/ +0./ +0 Ma +0 +/ Ma +,*** +,,** m +33, +/ +-./ Ma,**1 +,,** m, +,,** m,,.** m Fig., A,**1 Fig. - + :,,.** m -, 0** m +313 ; +32+ ; Yamamoto, +33- A,* km NE-SW -, 0** m,., 2** m, 0,*** m., 2** m, 0,*** m, 1,,** m A +* km,**/;,**1 WNW-ESE, CE : Con-,**1 tracting and Expanding Spread : A +* +, km - 3 +, km -+.* km -* km Fig. + -*,** m A,** m 1 /.* km Fig. + +,0 km +./, km Table + 277

4 Table +. Data acquisition parameters (A) and survey line information (B) for the,**1 West of Noto Peninsula seismic survey. / m, CE +* m,** /** --,. bit Delta-Sigma AD Flip-Flop, / cm, +/* m : +,/** cu.in., Cluster: -** cu.in. - guns/,** cu.in. - guns,,*** psi, 0*. m :.2* cu.in., Cluster: +/* cu.in., guns/ 3* cu.in., guns,,*** psi, 0*. m 278

5 ,**1 Fig.,. Data acquisition by flip-flop two-ship shooting used in the,**1 west of Noto Peninsula seismic survey. Fig. -. A two-ship data acquisition layout along the seismic line A. Fig.. A +,,** m,,,.** m, 1,,** m Fig. / Line-A * A CMP B.*. km

6 Fig... Example of shot gathers obtained by a two-ship method at constant distance spread. Fig. /. Examples of shot gathers obtained by a two-ship method at contraction and expanding spread. 280

7 ,**1.+ 0,. km /*. km +,./ m,/ /* m ,./ m A Trace Jittering Fig. 0 A Table, SuperX Fig. 1 A B., Fig. 0. Flow chart of data-processing of the,**1 west of Noto Peninsula seismic survey. 281

8 Table,. Processing parameters for the seismic data of the west of Noto Peninsula. e. g. Pe- Yilmiz, +321 Foster and gleg Mosher, +33, Fig. 2 External.-,,.** m ++.* km A Pegleg A +,.* km External +,. +/. km 282

9 ,**1 Fig. 1. The schematic description of trace interpolation in common-location domain and a comparison of CMP stacked profiles before and after spatial trace interpolation. NMO Fig. +* Fig. +* 1.* km LTI : Linear Traveltime Interpolarion method, Asakawa and Kawanaka, +33- SIRT Simultaneous Iterative Reconstruction Method; Zhu, +33, Fig. 3 A / /+.. A A CE Contracting and Ex-. 0km panding ++ km,,.** m / km,/ km, -km Figs km +, km Figs. +2,* seismic faces 283

10 Fig. 2. A comparison of CMP stacked profiles before and after the suppression of surface-related multiples based on the parabolic radon transform and model-trace extraction. N+* E +32, ; Yamaji, +33* ; Sato and Amano, +33+ Fig.,+ : : Fig.,+ Fig.,+ A,**/ D :,**/ D,**/ C,**/ N2 Blow, +303 B 284

11 ,**1 Fig. 3. Velocity structure along the line A. (A) Initial velocity model for tuning-ray tomography. (B) Final velocity model estimated by tuning-ray tomography. (C) Interval velocity model estimated by refraction velocity analysis. A Vc; Fig.,,,**/ A B C Fig. 3 B CMP,*** /, A NNW-SSE A FN, 1,,** m FN, FR+ Fig.,, P Fig. 3,- CMP-*/*,**/,**1 CMP,*** FN+ CMP+*** Fig.,-; 285

12 Fig. +*. Processing flow for deeper reflection profile along the seismic line A. Fig. ++. Migrated time section and depth converted seismic section of the line A. Based on the data acquired by two-ship standard reflection survey. 286

13 ,**1 Fig. +,. Migrated time section and depth converted seismic section of the line B.,**1 A CMP+3** FR, Fig.,.,**1 /- Fb+ B Fig. +, : FR+ A Fig. +, C Fig. +-: 287

14 Fig. +-. Migrated time section and depth converted seismic section of the line C. Fc+ Fc, Fig.,. Fc, CMP,**1 +//* FR+ D Fig. +. :,**1 AB A-C C CMP,*** FR- FR. FR. B FR, FR- B Y,**/ 288

15 ,**1 Fig. +.. Migrated time section and depth converted seismic section of the line D. Fd+ Fd,; Fig.,. E Fig. +/ : D, Fig. +1: FR-- FR- F, -+ F, R-+. Fe- Fe.. FR, + Fig.,/ Fig.,/ FR. B /. Fe B Fig / + Fig. +0 : CMP,/** 1- A, 1-B-. CMP,*** 1-. Fig. +2: F+ R-+ F+ R, B 1- / Fig. +3 : CMP+***,/** 289

16 Fig. +/. Migrated time section and depth converted seismic section of the line E. Fig. +0. Migrated time section and depth converted seismic section of the line +. CMP 1- A, Fig. +3:,+**,0/* 290

17 ,**1 Fig. +1. Migrated time section and depth converted seismic section of the line,. Fig. +2. Migrated time section and depth converted seismic section of the line

18 Fig. +3. Migrated time section and depth converted seismic section of the line 1- / and A-,. Fig.,*. Migrated time section and depth converted seismic section of the line 1--B

19 ,**1 Fig.,+. An example of geologic interpretation of the seismic section of the west of Noto Peninsula (Line E). 1-B- Fig.,* : +310; CMP +/** +313 ; +32+ ; Yamamoto et al., +33-; Fig.,0 Itoh and Nagasaki, +330 FB+ N-* W,**1 Kobayashi and Nakamura, +312 ; +33+ FR+ CMP,3** 0 / +* km +, km NE-ENE-WSW ABC C Fig.,1 293

20 Fig.,,. Seismic sections of the line A, acquired by two-ship deep reflection survey, and its geologic interpretation. A: Migrated time section, B; Depth converted section, C: Geologic interpretation. 294

21 ,**1 Fig.,-. Comparison between aftershock distribution and deep seismic section of the Line A. Hypocenters of aftershocks within, km from the seismic line were projected on to the section. Data of hypocenters are shown in red circle after Sakai et al. (,**2) and blue circle after Yamada et al. (,**2). A ABC, km Fig.,- A, km.* +* km 0* Sakai et al.,,**2,**1 1,**1 ENE-WSW 0* /*,**1 +3 : 295

22 Fig.,.. Geologic interpretation of the seismic sections Line B to D. 296

23 ,**1 Fig.,/. Geologic interpretation of the seismic sections Line E, Line + and,. Fig.,0. Geologic interpretation of the seismic sections by JNOC ( +31-) seismic data. 297

24 Fig.,1. Blowup of the seismic section of Line C, showing the late Miocene shortening deformation. 3/.,**1,**1 : 2,,-1,/..,**1,** /0, /00.,**1,**1 2, -*+ -+,. +32, / + +,+ p. Itoh, Y. and Y. Nagasaki, +330, Crustal shortening of southwest Japan in the late Miocene, The Island Arc, /, --1 -/-. +3,**1 Kano, K., T. Yoshikawa, Y. Yanagisawa, K. Ogasawara and : T. Danhara,,**,, An unconformity in the early Miocene syn-rifting succession, northern Noto Peninsula, Japan : Evidence for short-term uplifting precedent to the rapid opening of the Japan Sea, The Island Arc, ++, +1* ,,/,,0.,**/ Allmendinger, R.W. and J.H. Shaw,,***, Estimation of fault ++. / *. propagation distance from fold shape : Implications for Kato, A., S. Sakai, T. Iidaka, T. Iwasaki, E. Kurashimo, T. earthquake hazard assessment, Geology,,2, +*33 ++*,. Igarashi, N. Hirata, T. Kanazawa, and Group for the Asakawa, E. and T. Kawanaka, +33-, Seismic ray tracing aftershock observations of the,**1 Noto Hanto Earthusing linear traveltime interpolation, Geophys. Prosp., quake,,**2, Three-dimensional velocity structure in.+, the source region of the Noto Hanto Earthquake in,**1 Blow, W.H., +303, Late middle Eocene to recent planktonic imaged by a dense seismic observation, Earth Planets foraminiferal biostratigraphy, In Proc. + st Internat. Space, 0*, +*/ ++*. Conf. Planktonic Microfossils, Geneva, Proc., v. +, edited Kato, N., H. Sato, T. Imaizumi, Y. Ikeda, S. Okada, K. Kagoby P. Bronnimann, and H.H. Renz, pp. +33.,,, Leiden, hara, T. Kawanaka and K. Kasahara,,**., Seismic refle- Netherlands. ction profiling across the source fault of the,**- North- Foster, D. J. and C.C. Mosher, +33,, Suppression of multiple ern Miyagi earthquake (Mj 0.. ), NE Japan: basin inverreflections using the Radon transform, Geophysics, /1, sion of Miocene back-arc rift, Earth Planets Space, /0, -20-3/. +,// +, , Kato, N., H. Sato and N. Umino,,**0, Fault reactivation and -1 2/ active tectonics on the fore-arc side of the back-arc rift 298

25 ,**1 system, NE Japan, Journal of Structural Geology,,2, the crystalline crust from a two-ship normal-incidence,*++,*,,. and wide-angle experiments, Tectonophysics,,20, 13,**/ ,20, Kobayashi, Y. and K. Nakamura, +312, Restoration of tectonic +313 stress field of Tertiary Southwest Japan by means of dikes, Abs. Intn. Geodynamics Cinf., ,**1 no ,/ 1-0. CD,**1,**1 Sakai, S., A. Kato, T. Iidaka, T. Iwasaki, E. Kurashimo, T. 2,,//,0.. Igarashi, N. Hirata, T. Kanazawa and the group for the Tsuru, T., Miura, S., Park, J.O., Ito, A., Fujie, G., Kaneda, Y., joint aftershock observation of the,**1 Noto Hanto No, T., Katayama, T. and Kasahara, J.,,**/, Variation of Earthquake,,**2, Highly resolved distribution of after- physical properties beneath a fault observed by a twoshocks of the,**1 Noto Hanto Earthquake by a dense ship seismic survey o# southwest Japan, Jour. Geoseismic observation, Earth Planets Space, 0*, phys. Res., ++*, B */.*/, doi: +*. +*,3 /,**. JB **-*-0. Sato, H. and K. Amano, +33+, Relationship between tecton- Yamada, T., K. Mochizuki, M. Shinohara, T. Kanazawa, S. ics, volcanism, sedimentation and basin development, Kuwano, K. Nakahigashi, R. Hino, K. Uehira, T. Yagi, N. Late Cenozoic, central part of Northern Honshu, Japan, Takeda and S. Hashimoto,,**2, Aftershock observation Sediment. Geology, 1., -,--.-. of the Noto Hanto earthquake in,**1using ocean bot- Sato, H., N. Hirata, T. Ito, N. Tsumura and T. Ikawa, +332, tom seismometers, Earth Planets Space (in press). Seismic reflection profiling across the seismogenic fault Yamaji, A., +33*, Rapid intra-arc rifting in Miocene northof the +33/ Kobe earthquake, southwestern Japan. Tec- east Japan, Tectonics, 3, -0/ -12. tonophysics,,20, +3-*. Yamamoto, H., +33-, Submarine geology and post-opening tectonic movements in the southern region of the Sea,**+ of Japan. Marine Geology, ++,, +-- +/*. ++* , ,**1 Yilmaz, O., +321, Seismic data processing, Society of Exploration,**1 Geophysicists, /,/ p. 2, Zhu, X., +33,, Tomostatics: Turing-ray tomography and static corrections, The Leading Edge, ++, +/,-. +/ p, 2 Received February 1,,**2 Singh, C.S., P. J. Hague and M. McCaughey, +332, Study of Accepted March +1,,**2 299