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Geomorphology and geology around the Fukushima Daiichi NPS Principal Scientist at Geological Survey of Japan, AIST Atsunao MARUI 1

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Geomorphology and geology around the

Fukushima Daiichi NPS

Principal Scientist at Geological Survey of Japan, AIST

Atsunao MARUI

1

Contents

1.Geomorphology alound Fukushima Daiichi Nuclear Power Station

2.Outline of the Geological Survey 3.Geology alound Fukushima Daiichi

Nuclear Power Station 4.Water level and Quality of the Aquifers

2

Geomorphology(Japanese Islands)

3

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

4

■Neogene volcanic rocks of the Izu-Bonin Arc

■Neogene accretionary complex

■Tertiary low-P type metamorphic rocks

■Creraceous to early Cenozoic sedimentary rocks in Chidori Arc

■Cretaceous to Paleogene accretionary complex

■Cretaceous high-P type metamorphic rocks

■Cretaceous low-P type metamorphic rocks

■Jurassic to Cretaceous accretionary complex and sedimentary rocks

■Jurassic accretionary complex

■Geology including several categories below

■Triassic to Jurassic high P-type metamorphic rocks

■Permian to Triassic sedimentary rocks and mafic to ultramafic rocks

■Permian accretionary complex

■Permian to Triassic accretionary complex

■Carboniferous high-P type metamorphic rocks and mafic to ultramafic rocks

■ Early Carboniferous accretionary complex

■Ordovician to Triassic sedimentary and metamorphic rocks

■Proterozoic to Paleozoic metamorphic and granite rocks

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.

by Geological Survey of Japan, AIST

https://www.gsj.jp/geology/geomap/geology-japan/ <Main Petrology>

Geology (Whole Japan)

Geological Map of the Area

5

Fukushima Daiichi Nuclear Power Station

Pacific Ocean

Futaba-Fault

Granites Sediments

The Futaba fault crushing belt, that is

approximatery 80-km long, is located on

the 8 km west of the NPS. Abukuma

mountains are composed by plutonic

rocks like granite, in the west of the

crushing belt.

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.

Geomorphology of the Plant Area

Fukushima Daiichi-NPS

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.

Divide

River

River

River

River

Divide

Ohkura

Dam

The Area located higher than

Fukushima Daiichi-NPS

6

Boring Points

7

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

C-1

Boring point (Before 11th March 2011)

Boring point (After 11th March 2011)

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)

Ta

ka

oka

str

atu

m

Geology of the Plant Area

8

◇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

Geological Cross Section of the Fukushima Daiichi Nuclear Power Station

Mudstone stratum (Stratum II)

Middle-grained sandstone

Stratum (Stratum I)

Alternate strata (Stratum III)

Mudstone stratum (Stratum IV)

Original topography

Geology Legend Landfill

Terrace deposit of Quaternary period

Middle-grained sandstone in T3 member of Tomioka stratum(Stratum I)

Mudstone stratum in T3 member of Tomioka stratum(Stratum I, II and IV)

Alternate strata in T3 member of Tomioka stratum(Stratum III)

Fine-grained sandstone stratum in T3 member of Tomioka stratum(Stratum IV)

Coarse-grained sandstone stratum in T3 member of Tomioka stratum(Stratum IV)

T2 member of Tomioka stratum

Tuff Key Bed

Cross Sectional View (E-W Section)

Horizontal: Vertical=1:10

Mudstone stratum contained

in middle-grained sandstone

Alternate strata

(Stratum I)

Middle-grained sandstone

(Stratum I)

Level of water within hole

and groundwater Section

Section

Cross section ③-③’

(Current analysis model)

9

Cross Sectional View(N-S Section)

H:W=1:10 Section

Geology Legend Landfill

Terrace deposit of Quaternary period

Middle-grained sandstone in T3 member of Tomioka stratum(Stratum I)

Mudstone stratum in T3 member of Tomioka stratum(Stratum I, II and IV)

Alternate strata in T3 member of Tomioka stratum(Stratum III)

Fine-grained sandstone stratum in T3 member of Tomioka stratum(Stratum IV)

Coarse-grained sandstone stratum in T3 member of Tomioka stratum(Stratum IV)

T2 member of Tomioka stratum

Tuff Key Bed

Mudstone stratum contained

in middle-grained sandstone

Level of water within hole

and groundwater

Middle-grained sandstone

(Stratum I)

(Current analysis model)

Alternate strata

(Stratum I)

Section

Section

Horizontal: Vertical=1:10 Cross section ⑭-⑭’

10

16.7

28.0

29.7

7.6

7.8

9.3

5.8

34.6

34.2

34.1

28.1

32.8

33.3

33.8

34.0

34.1

34.5

34.1

35.0

35.1

35.2

35.4 35.5

34.3

31.7

34.2

34.0

33.0

31.432.7

32.4 34.3

35.2

35.0 34.4

4.85.8 5.7 5.8 4.3 3.9 3.7 5.3 4.8

3.9

7.7

7.68.7

6.86.7

7.5

3.0 2.4 2.8

11.5 11.4 11.411.6

12.4

13.0 18.616.0

21.7

22.8

24.9

10.0

9.9

9.9

7.87.3

10.0

30m

25m

20m

15m

10m

5m

35.0

35.1

35m

24.0

Water Table in the Mid-sand Layer

※Continuous data before 2012 were

plotted on the 4-m plane, and new

observed data from 2013 is used in the

other area

・Level is described by O.P.m

・O.P.m indicates the mean sea

level of Onahama bay, before the

earthquake.

Boreholes to middle-grained sandstone stratum

Boreholes to alternate strata

Boreholes to middle-grained sandstone stratum and alternate strata

Boreholes to fine-grained sandstone stratum

Water-quality monitoring holes

Planning holes

Grouting area

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

Date of collection 2013

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

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

Unit 1 Turbine bldg.

Unit 2 Turbine bldg.

Unit 3 Turbine bldg.

Unit 4 Turbine bldg.

R/B R/B R/B R/B

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

R/B : reactor bldg.

12

Cross section view of the water quality check point

◇Screen locations of the Well A to C on the 35-m Plane

A-1

A-2

A-3

A-4

B-1

B-2

B-3

B-4

C-1

C-2

C-3

C-4

250m 360m 250m 400m

Mid-sand(StratumⅠ)

Mud Layer(StratumⅣ)

Fine-sand(StratumⅣ)

Coarse-sand(StratumⅣ) Hole A

Hole B

Hole C

May 2013

Mud Layer(StratumⅡ)

Altanative Strata(StratumⅢ)

Terrace Sediments

13

Water Quality of Aquifers (Well A-C)

C-4

10 5 0 5 10

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

(meq/L)

C-3

10 5 0 5 10

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

(meq/L)

C-2

10 5 0 5 10

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

(meq/L)

C-1

10 5 0 5 10(meq/L)

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

B-1

10 5 0 5 10(meq/L)

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

B-2

10 5 0 5 10

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

(meq/L)

B-3

10 5 0 5 10

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

(meq/L)

B-4

10 5 0 5 10

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

(meq/L)

A-4

10 5 0 5 10

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

(meq/L)

A-3

10 5 0 5 10

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

(meq/L)

A-2

15 5 5 15

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

(meq/L)

A-1

10 5 0 5 10(meq/L)

Na+

Mg2+

Ca2

Cl-

(SO4)2-,NO3-

HCO3-

pH:6.5

EC:21mSV/m

Alternate Strata

(StratumⅢ)

Fine and Coarse Sand Layer

(StratumⅣ)

H24.2.8 Samp 2.14 Ana

H25.12.23 Samp 1/7 Ana

pH:6.7

EC:24mSV/m

pH:6.3

EC:40mSV/m

pH:6.4

EC:40mSV/m

pH:6.2

EC:88mSV/m

pH:6.5

EC:75mSV/m

pH:8.4

EC:14mSV/m pH:8.7

EC:14mSV/m

pH:6.7

EC:21mSV/m pH:6.7

EC:22mSV/m

pH:8.2

EC:15mSV/m pH:7.5

EC:14mSV/m

pH:6.8

EC:18mSV/m

pH:6.9

EC:24mSV/m

pH:6.7

EC:21mSV/m

pH:6.7

EC:22mSV/m

pH:7.6

EC:17mSV/m

pH:9

EC:17mSV/m

pH:6.2

EC:21mSV/m

pH:6.3

EC:18mSV/m

pH:6.1

EC:50mSV/m pH:6.4

EC:39mSV/m

pH:6.2

EC:70mSV/m

pH:6.2

EC:75mSV/m

Point of quick

responses to

rainfall Middle grained

sandstone stratum

(StratumⅠ)

14

Conclusion

Fukushima Daiichi-NPS

Divide

River

River

River

River

Divide

Ohkur

a Dam

15

●Almost all (at least upper than

alternative layer) Groundwater is

generated by rainfall.

・annual rainfall 1400mm

・annual evapotranspilation 600mm

・direct discharge 20%

・generated groundwater per yr

・groundwater discharge cross

the coastal line

●1200 t groundwater was

discharged to the ocean by sub-

drain system around buildings to

keep the groundwater level lower

than floor level (below sea level)

before the accident

◎Groundwater is the most

important issue on the Fukushima

Daiichi Nuclear Power Station

Original groundwater level

Alternative layer

Original ground surface