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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
K
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