Geomorphology and Geology Around the Fukushima Daiichi NPS

Japanese Islands are located in the North-West margin of the Pacific Ocean, and it’s a part of a huge mountain chain. It constitutes island arc-trench system with some deep trenches. The islands can be divided to North-East and South-West by the terrain characteristics. North-East Japan; the axis of mountains and basins are expands to north-south direction, and volcanic front is located in the center of Tohoku District. South-West Japan; Median Tectonic Lime characterize the terrain of south (highly mountain area) and north area (smooth area) of MTL, by Geographical Survey Institute, MLIT http://www.gsi.go.jp/atlas/atlas-etsuran.html

3 Geology （Whole Japan） Japanese Islands are located on the margin of the Eurasian Plate, and influenced by the sinking of Pacific Plate in the long term. That’s why; 1. Accretionary prism is the feature of the geology of Japanese Islands. 2. Basement of the islands are the older in the continental side, and the newer in the Pacific side. 3. Variable volcanic deposits are deposited in the whole islands. The exact depth and distribution of the basement in the North-East Japan is not clear, because of the thickness of the accretionary prism and the volcanic deposits.

https://www.gsj.jp/geology/geomap/geology-japan/ ■Neogene volcanic rocks of the Izu-Bonin Arc ■Geology including several categories below ■Neogene accretionary complex ■Triassic to Jurassic high P-type metamorphic rocks ■Tertiary low-P type metamorphic rocks ■Permian to Triassic sedimentary rocks and mafic to ultramafic rocks ■Creraceous to early Cenozoic sedimentary rocks in Chidori Arc ■Permian accretionary complex ■Cretaceous to Paleogene accretionary complex ■Permian to Triassic accretionary complex ■Cretaceous high-P type metamorphic rocks ■Carboniferous high-P type metamorphic rocks and mafic to ultramafic rocks ■Cretaceous low-P type metamorphic rocks ■ Early Carboniferous accretionary complex ■Jurassic to Cretaceous accretionary complex and sedimentary rocks ■Ordovician to Triassic sedimentary and metamorphic rocks ■ Jurassic accretionary complex ■Proterozoic to Paleozoic metamorphic and granite rocks 4 Geological Map of the Area

Futaba-Fault

Fukushima Daiichi Nuclear Power Station

The Futaba fault crushing belt, that is approximatery 80-km long, is located on Granites Sediments the 8 km west of the NPS. Abukuma mountains are composed by plutonic rocks like granite, in the west of the crushing belt. Pacific Ocean A Neogene, Tomioka function is widely lays on the hills of the eastern side, anti- and syn-cline structures are observed in some area, however, faults and folda are not indicated. The Neogene Functions are declined 1- to 2- degree to the east ocean side, totally. 5 Geomorphology of the Plant Area

The plant is located in the 35-m high table land surrounded by rivers, and the plant buildings are standing on the 10-m high developed plane.

River The Area located higher than Fukushima Daiichi-NPS Divide River

Divide

Fukushima Daiichi-NPS

Ohkura Dam River

River

6 Boring Points ◇3-dimensional geological model is constructed by using over than 200 boring data, before and after the earthquake.

Boring point (Before 11th March 2011) Boring point (After 11th March 2011)

Ｃ－１

Legend

Alluvium/landfill Low terrace deposit (L face group) Middle terrace deposit (M face group) Middle-grained sandstone stratum (Stratum I) Mudstone stratum(stratum II) / alternate Submarine landside Strata (stratum III)

deposit

Sandy mudstone to greywacke

(Strata IV to VI) Takaoka stratumTakaoka 7 Geology of the Plant Area

◇Neogene layers, so-called Tomioka Strata, are existed under the terrace deposit in the NPS plant area. ◇Tomioka Strata is composited by Middle-grained sandstone stratum, Mudstone stratum, Alternate strata and some from the top. ◇All layers under the Middle-grained sandstone stratum are deposited parallel and decline to the ocean

Middle-grained sandstone Stratum (Stratum I) Original topography

Mudstone stratum (Stratum II)

Alternate strata (Stratum III)

Mudstone stratum (Stratum IV)

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Geological Cross Section of the Fukushima Daiichi Nuclear Power Station

8 Cross Sectional View (E-W Section)

Cross section ③－③’ Horizontal: Vertical=1:10 Geology Legend Landfill Section Terrace deposit of Quaternary period Mudstone stratum contained Level of water within hole Middle-grained sandstone in T3 member of Tomioka stratum(Stratum I) in middle-grained sandstone and groundwater

Section Mudstone stratum in T3 member of Tomioka stratum(Stratum I, II and IV) Middle-grained sandstone Alternate strata in T3 member of Tomioka stratum(Stratum III) (Stratum I) Fine-grained sandstone stratum in T3 member of Tomioka stratum（Stratum IV） (Current analysis model) （） Coarse-grained sandstone stratum in T3 member of Tomioka stratum Stratum IV Alternate strata T2 member of Tomioka stratum (Stratum I) Tuff Key Bed 9 Cross Sectional View（N-S Section）

Cross sectionSection ⑭－⑭’ Horizontal:H:W= Vertical=1:10 1:10

Geology Legend Landfill Section Terrace deposit of Quaternary period Mudstone stratum contained Level of water within hole Middle-grained sandstone in T3 member of Tomioka stratum(Stratum I) in middle-grained sandstone and groundwater

3.0 2.4 2.8 ※Continuous data before 2012 were ・Level is described by O.P.m plotted on the 4-m plane, and new observed data from 2013 is used in the ・O.P.m indicates the mean sea other area 3.9 4.8 level of Onahama bay, before the 5.8 5.7 5.8 4.3 3.9 3.7 5.3 4.8 earthquake. 5m 7.5

5.8 7.7 6.7 6.8

7.6 8.7 7.8 7.6 7.3

10m 10.0 9.9 7.8 11.5 11.4 11.4 10.0 9.9 11.6 12.4 9.3 13.0 18.6 16.0 15m 21.7 22.8 24.0 16.7 24.9

29.7 28.0 20m

33.0

25m 34.0

31.4 31.7 32.7 30m 35.2

32.4 34.2 34.3 35.0 34.4

32.8 34.1 34.6

28.1 33.3 34.2 33.8

34.0 34.3 34.1 Boreholes to middle-grained sandstone stratum 34.5 Boreholes to alternate strata 34.1 35.1 Boreholes to middle-grained sandstone stratum and alternate strata 35m 35.0 Boreholes to fine-grained sandstone stratum 35.0 Water-quality monitoring holes 35.1 Planning holes 35.2 Grouting area 35.4 35.5 Sea-side impermeable walls 11 Dose Rate of the Groundwater around Build. #1 to #4

Monitoring wells

Sea-side Land-side

Unit 1 Unit 2 Unit 4 Unit 1 Unit 2 Unit 3 Unit 4

1T-1 1T-2 1T-3 1T-4 1T-5 1T-6 2T-1 2T-2 4T-1 1R-1 2R-1 3R-1 4R-1

2013 Date of collection Sep. 5 Sep. 19 Sep. 5 Sep. 11 Sep. 13 Oct. 1 Dec. 2 Sep. 11 Sep. 11 Sep. 9 Sep. 5 Sep. 3 Sep. 25 Sep. 18

Time of collection 13:00 12:15 11:00 11:50 10:00 10:45 10:30 13:00 11:35 10:30 12:50 10:00 11:00 9:20

Cs-134 ND(0.37) ND(0.38) ND(0.54) ND(0.46) 0.64 ND(0.47) ND(0.82) ND(0.36) ND(0.47) ND(0.38) 0.64 ND(0.55) ND(0.43) ND(0.46) Cs-137 ND(0.47) ND(0.45) ND(0.52) 0.88 0.90 ND(0.62) ND(0.84) 0.66 ND(0.60) ND(0.44) 1.3 0.97 ND(0.58) ND(0.59) Gross β ND(21) ND(18) ND(21) 9,500 7,000 3,200 13,000 ND(24) 830 ND(17) ND(21) 36 ND(17) ND(18) Tritium (H-3) 200 200 80,000 2,700 4,200 7,500 3,300 20,000 770 1,800 150 311 1,100 ND(7)

Sr-90 0.90 1.3 1.1 7,500 - 2,900 8,700 0.36 740 ND(0.28) 0.46 2.4 ND(0.26) ND(0.28)

＊ND represents a value below the detection limit; values in ( ) represent the detection limit R/B : reactor bldg.

Date of collection: Sep. 3 ~ Dec. 2. 2013

1T-4 1T-6 1T-5

1T-1 1T-3 2T-1 2T-2 1T-2 4T-1 Unit 1 Unit 2 Unit 3 Unit 4 Turbine bldg. Turbine bldg. Turbine bldg. Turbine bldg.

R/B 1R-1 R/B R/B R/B 4R-1 3R-1 2R-1 12 Cross section view of the water quality check point ◇Screen locations of the Well A to C on the 35-m Plane

400m 250m 360m 250m

Terrace Sediments

C-4 B-4 Mid-sand（StratumⅠ） A-4

A-3 B-3 C-3

Mud Layer（StratumⅡ）

B-2 C-2 A-2 Altanative Strata（StratumⅢ）

A-1 B-1 Fine-sand（StratumⅣ） C-1 Hole A Hole C Coarse-sand（StratumⅣ） Hole B Mud Layer（StratumⅣ）

May 2013 13 Water Quality of Aquifers (Well A-C)

pH：6.5 ：：：：： A-4 pH 6.7 pH 6.2 pH 6.3 pH 6.2 C-4 pH 6.2 EC：21mSV/m EC：24mSV/m EC：21mSV/m B-4 EC：18mSV/m EC：70mSV/m EC：75mSV/m Na+ Cl- Na+ Cl- Na+ Cl- H24.2.8 Samp 2.14 Ana Point of quick

H25.12.23 Samp 1/7 Ana Ca2 HCO3- Ca2 HCO3- responses to Ca2 HCO3- rainfall Middle grained (SO4)2-,NO3- Mg2+ Mg2+ (SO4)2-,NO3- Mg2+ (SO4)2-,NO3- sandstone stratum (meq/L) (meq/L) （StratumⅠ10） 5 0 5 10 10 5 0 5 (meq/L)10 10 5 0 5 10

： pH：6.3 A-3 pH 6.4 pH：6.1 pH：6.4 pH：6.8 C-3 pH：6.9 ： B-3 EC：40mSV/m EC 40mSV/m EC：50mSV/m EC：39mSV/m EC：18mSV/m EC：24mSV/m Na+ Cl- Na+ Cl- Na+ Cl-

Ca2 HCO3- Ca2 HCO3- Ca2 HCO3-

Mg2+ (SO4)2-,NO3- Mg2+ (SO4)2-,NO3- Mg2+ (SO4)2-,NO3- (meq/L) 10 5 0 5 10 10 5 0 5 (meq/L) 10 10 5 0 5 (meq/L)10

： pH：6.2 A-2 pH 6.5 pH：6.7 B-2 pH：6.7 pH：6.7 C-2 pH：6.7 EC：88mSV/m EC：75mSV/m EC：21mSV/m EC：22mSV/m EC：21mSV/m EC：22mSV/m Na+ Cl- Na+ Cl- Na+ Cl- Alternate Strata （StratumⅢ） Ca2 HCO3- Ca2 HCO3- Ca2 HCO3- Mg2+ (SO4)2-,NO3- Mg2+ (SO4)2-,NO3- Mg2+ (SO4)2-,NO3-

15 5 5 (meq/L)15 10 5 0 5 (meq/L)10 10 5 0 5 (meq/L)10

pH：8.4 A-1 pH：8.7 pH：8.2 B-1 pH：7.5 pH：7.6 C-1 pH：9 EC：14mSV/m EC：14mSV/m EC：15mSV/m EC：14mSV/m EC：17mSV/m EC：17mSV/m Na+ Cl- Na+ Cl- Na+ Cl- HCO3- Ca2 HCO3- Ca2 HCO3- Ca2 Mg2+ (SO4)2-,NO3- Mg2+ (SO4)2-,NO3- Mg2+ (SO4)2-,NO3- Fine and Coarse Sand Layer (meq/L) 10 5 0 5 10 (meq/L) 10 5 0 5 (meq/L)10 （StratumⅣ） 10 5 0 5 10 14 Conclusion

●Almost all (at least upper than River alternative layer) Groundwater is Divide River generated by rainfall. Divide Fukushima ・annual rainfall 1400mm Daiichi- ・annual evapotranspilation 600mm NPS ・direct discharge 20% Ohkur ・generated groundwater per yr a Dam River ・groundwater discharge cross River the coastal line

●1200 t groundwater was Original groundwater level discharged to the ocean by sub- Original ground surface drain system around buildings to keep the groundwater level lower Alternative layer than floor level (below sea level) before the accident

◎Groundwater is the most important issue on the Fukushima Daiichi Nuclear Power Station