米国における活断層及び液状化痕跡の掘削調査工事

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1 No. 2, p , 2002 Geoslices of sand blows and their potential source beds at the New Madrid seismic zone, central United States Eugene Schweig 5 Brian Atwater 6 Laurel Mayrose 7 Martitia Tuttle 8 9 Keita Takada 1, Kenji Satake 2, Koichi Shimokawa 3, Koji Okumura 4, Eugene Schweig 5, Brian Atwater 6, Laurel Mayrose 7, Martitia Tuttle 8 and Tsuyoshi Haraguchi 9 1 NEDO For Fault Research Center, GSJ/AIST, present affiliation: Fukken Co. Ltd., takada@fukken.co.jp 2, 3 Active Fault Research kenji.satake@aist.go.jp, Center, GSJ/AIST, k.shimokawa@aist.go.jp 4 Hiroshima ok@hiroshima-u.ac.jp Univ., koji 5, 6 U.S. schweig@ceri.memphis.edu, Geological Survey, atwater@u.washington.edu) 7 The University s, lmayrose@memphis.edu) of Memphi 8 M. Tuttle & AssociatesM. Tuttle & Associates, mptuttle@erols.com 9 Fukken Co. Ltd., haraguchi@fukken.co.jp Abstract: A US-Japan team made geoslicer surveys of liquefaction features in the New Madrid seismic zone of the central United States in the fall of 2001, with hopes of improving methods for estimating ground motions from historic and prehistoric earthquakes. Large earthquakes occurred on December 16 (twice), 1811, and on January 23 and February 7, 1812 at the New Madrid seismic zone. Ground shaking from these earthquakes, which were felt as far away as on the Atlantic coast and Gulf of Mexico, produced thousands of sand blows on floodplains of the Mississippi River and nearby streams in an area at least 80 km by 200 km. Prehistoric sand blows, recognized in part by stratigraphic relations with Native American horizons and features, show that earthquake sequences produced similar liquefaction fields in this area about A.D and The geoslicing was done at two sites near Blytheville, Arkansas (sites JP and HF). A trench at the JP site, excavated by USGS and the University of Memphis, showed a sand blow of fine to medium sand with many mud clasts. On the ditch wall at the HF site, a sand blow intrudes a paleosol containing artifacts about 1 m below the surface, and almost reaches the ground surface. Using long and wide slicers, we extracted soil sections including liquefaction features. The stratigraphy in the slices at each site shows that the sand blows came from depths of 7 m or more. A sand blow on the ditch wall (HF site) continues to a dike observed in the slice 4 m beneath. Detrital wood in the highest potential source sand beneath the JP site gave radiocarbon ages corresponding to A.D and A.D These ages show that the sand was shaken not only in but perhaps also during the earthquake sequence of A.D Keywords: New Madrid seismic zone, liquefaction, sand blow, paleoseismology, geoslicer New Madrid seismic zone USGS 5 UM Reelfoot rift

2 Eugene weigbrian Atwater Laurel May rosemar Sch titia Tuttle Obermeier, 1989 JP 30m 150m M 7.5 USGS UM m 2m 1.5m (1) Marked Tree, Ark. Caruthersville, Mo. 100km Fig. 4 -(2) Ridgely, Tenn.New mud Madrid, clast Mo. - dike cm (3) Charleston, Mo HF 2m 1m Obermeier, m 2m 1m Fig. 1A Tuttle et.al., 1998, JP 2000; Tuttle and Schweig, 1995; Obermeier, 1996, Obermeier and Pond, 1999 Fig. 1B USGS Atkinson et al., 2000; Schweig and Ellis, 1994; Johnston and Nava, cm 9.14m 15cm Sheetpile 6 1.2m 2.0m 1.5m Blytheville 4.0m Fig. 2A, B 50t ICE model 416 Yarbro Pemiscot Bayou Fig. 2C Joe s Pond JP JP 8cm 1% JP-5 500Haynes 57cm Field 7%JP-4 HF HF Fig. 1B 13cm 2%HF-S m

3 23%HF-N-2 Table HF-N-2 1 8% JP-4 50cm USGS-UM JP-5 7.4m 7.9m 14 C Fig. 3A, B A.D , A.D Mayrose et al., JP-14JP-3 2 JP-7 8 1m HF 6 2 JP-5, unit unit 1, 3, 5 2, 4, 6 6 Fig. 6 unit 1 unit 3 JP ditch 2 unit 5 Fig. 3C 3 HF-S-13 1 HF-S-W-1 unit 2 unit 4 100m Fig. 6A 35cm 2 HF-N-1, 2 Fig. 6Aunit 6 Fig. 6B HF-S- 4m Fig. HF-S-2 7 unit 2 2m unit 13 unit 2 unit 4 JP 7m unit 1unit 2 Fig. 5 unit 6 unit 1 HF-S-3 unit 4 unit 5 7m unit 2

4 Eugene weigbrian Atwater Laurel May rosemar Sch titia Tuttle 2m Johnston A.C. and S.J. Nava (1985) Recurrence rates and probability estimates for the New Madrid seismic zone. J. Geophys. Res. 90, Mayrose, L., E. Schweig, M.P. Tuttle, M. Haynes, T. Haraguchi, K. Satake, K. Takada, K. Shimokawa, and K. Okumura (2002) Recent paleoliquefaction studies in the New Madrid seismic zone, central U.S (Abstract), Seism. Res. Lett., 73, C 1997 Geo-slicer., 106, Obermeier, S. (1989) The New Madrid earthquake: an USGS-UM engineering-geologic interpretation of relict liquefaction features. U.S. Geological Survey Professional Paper, 1336-R, 114pp. Obermeier, S. (1996) Using liquefaction-induced features for paleoseismic analysis. In J.P. McCalpin (ed.), Paleoseismology, Academic Press, G. Patterson Obermeier, S.F. and E. Pond (1999) Issues in using C. Payne M. Haynes USGS liquefaction features for paleoseismic analysis. S. Diehl D. Hoffman Seism. Res. Lett., 70, Schweig E.S. and M.A. Ellis (1994) Reconciling short recurrence intervals with minor deformation in the New Madrid (Missouri) seismic zone. Science, 264, Tuttle M.P., R.H. Lafferty III, and E.S. Schweig III (1998) Dating of the liquefaction features in the New Madrid seismic zone and implications for earthquake hazard. U.S. Nuclear Regulatory Commission, NUREG GR-0017, 77 pp. Tuttle M.P., J.D. Sims, K. Dyer-Williams, R. H. Lafferty Atkinson G., B. Bakun, P. Bodin, D. Boore, C. Cramer, A. III, and E. S. Schweig III (2000) Dating of the Frankel, P. Gasperini, J. Gomberg, T. Hanks, B. liquefaction features in the New Madrid seismic Herrmann, S. Hough, A. Johnston, S. Kenner, C. zone. U.S. Nuclear Regulatory Commission, Langston, M. Linker, P. Mayne, M. Peterson, C. NUREG GR-0018, 42 pp. Powell, W. Prescott, E. Schweig, P. Segall, S. Stein, Tuttle M.P. and E.S. Schweig (1995) Archeological and B. Stuart, M. Tuttle, and R. Van Arsdale (2000) pedological evidence for large prehistoric Reassessing the New Madrid seismic zone. Eos earthquakes in the New Madrid seismic zone, central Trans. AGU, 81, United States. Geology, 23,

米国ニューマドリッド地震帯における地震液状化層の調査第 1 図. ニューマドリッド地震帯における最近の地震活動 (A) と調査地点周辺の空中写真 (B). 震央分布 (1974-2000) は Center for Earthquake Research and Information (CERI) による. 空中写真は,U.S. Geological Survey: 10 Apr.

5 米国ニューマドリッド地震帯における地震液状化層の調査第 1 図. ニューマドリッド地震帯における最近の地震活動 (A) と調査地点周辺の空中写真 (B). 震央分布 ( ) は Center for Earthquake Research and Information (CERI) による. 空中写真は,U.S. Geological Survey: 10 Apr および 16 Feb を使用. Fig. 1. Index map of survey site. A: seismicity of New Madrid seismic zone, B: aerial photographs around the study site. The epicenter data ( ) are from Center for Earthquake Research and Information (CERI) and the aerial photographs were taken by U.S. Geological Survey on 10 April 1996 and 16 February 1994.

6 高田圭太佐竹健治下川浩一奥村晃史 Eugene Schweig Brian Atwater Laurel Mayrose Martitia Tuttle 原口強の打込みの打込みガイドクリップを矢板の継ぎ手に沿わせる ) 装置の解体をはずす地層抜き取りの完成 ( 表面整形の後観察 ) 装置の引き抜き ( 固定ピンでとを固定し振動をかけずに同時に引き抜く ) 第図. 調査方法の概要. ジオスライサー調査のながれ, ジオスライサーの断面形状, 試料短縮量の計測方法. 第表. 矢板型ジオスライサー試料の短縮 ( サイトおよびサイト ). サイトサイト

7 米国ニューマドリッド地震帯における地震液状化層の調査第 3 図. ジオスライサー掘削位置詳細図.A: JP サイトにおける掘削位置平面図,B: JP サイトにおける掘削位置断面図,C: HF サイトにおける掘削位置平面図. Fig. 3. Location maps of the geoslicer surveys. A: plan view of the JP site, B: cross-section view of the JP site, C: plan view of the HF site.

8 高田圭太佐竹健治下川浩一奥村晃史 Eugene Schweig Brian Atwater Laurel Mayrose Martitia Tuttle 原口強第 4 図.JP サイトトレンチで観察された噴砂構造. Fig. 4. Sand blow feature on the trench wall at the JP site.

9 第 5 図.JP サイトの試料スケッチ. Fig. 5. Logs of geoslices at the JP site. 米国ニューマドリッド地震帯における地震液状化層の調査

10 高田圭太佐竹健治下川浩一奥村晃史 Eugene Schweig Brian Atwater Laurel Mayrose Martitia Tuttle 原口強第 6 図.HF サイトの試料スケッチ. 写真 A, B の位置はスケッチ中に示す. Fig. 6. Logs and photos (A and B) of geoslices at the HF site.

11 米国ニューマドリッド地震帯における地震液状化層の調査第図. ダイクを含むジオスライサー断面 ().

米国における活断層及び液状化痕跡の掘削調査工事

米国における活断層及び液状化痕跡の掘削調査工事 No.2, p.235-243, 2002 Survey of tsunami deposits at an archaeological site along the eastern Nankai trough 1 2 3 4 5 6 7 Keita Takada 1, Kenji Satake 2, Akira Sangawa 3, Koichi Shimokawa 4, Hiroyuki Kumagai