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L o n g - t e r m g r o u n d w a t e r l e v e l c h a n g e s o n t h e f o c a l r e g i o n o f t h e 1 9 9 9 C h i - C h i e a r t h q u a k e , T a i w a n N

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SLIDE 1

L

  • n

g

  • t

e r m g r

  • u

n d w a t e r l e v e l c h a n g e s

  • n

t h e f

  • c

a l r e g i

  • n
  • f

t h e 1 9 9 9 C h i

  • C

h i e a r t h q u a k e , T a i w a n

○ N a

  • j

iK

  • i

z u m i ( G e

  • l
  • g

i c a l S u r v e y

  • f

J a p a n , A I S T ] , W e n

  • C

h i L a i , C h j e n g

  • L

u nS h i e h ( D i s a s t e r P r e v e n t i

  • n

R e s e a r c h C e n t e r , N C K U ) K u

  • C

h y n gC h a n g ( W a t e r R e s

  • u

r c e A g e n c y , T a i w a n ) T

  • s

h i h a r u Y a m a d a ( K a t s u j i m aC

  • .

L t d . )

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SLIDE 2

1 9 9 9C H I

  • C

H I E A R T H Q U A K E : M w 7 . 6 T I M E : 1 : 4 7 O N S E P 2 1 , 1 9 9 9 （L O C A L T I M E ） D E P T H : 6 ｋｍ S H A L L O W E A R T H Q U A K E I N T H E P L A T E B O U N D A R Y M A X I M U M S E I S M I C I N T E N S I T Y : 6 O R G R E A T E R I N J M A S C A L E D E A D > 2 , 3

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SLIDE 3

Program for Earthquakes and Program for Earthquakes and Active Active-

  • fault Research (PEAR)

fault Research (PEAR)

  • Seismogenic-zone structures
  • Earthquake geology
  • Seismicity and seismotectonics
  • Crustal deformations
  • Earthquake physics (including physics,

chemistry,rock mechanics, and

hydrology related to earthquakes)

  • Strong-motion seismology and

engineering seismology

2001-2005

DPRC,WRA (GSJ) 2006～

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SLIDE 4

★

N U M B E R > 5 5 R E S O L U T I O N : 1

  • ２ｃｍ

U N I F O R M I N V E S T I G A T I O N O F H Y D R O

  • G

E O L O G I C A L S T R U C T U R E 1 S T A T I O N H A S 2 O R 3 W E L L S . O N E I S S H A L L O W ( 5

  • 3

M ) T H E O T H E R S A R E D E E P ( 1

  • 3

M ) . ・P U M P I N G E F F E C T I S L A R G E . ・N O N

  • U

N I F O R M D I S T R I B U T I O N

F O C A L R E G I O N 6 6 S T A T I O N S 1 6 8 W E L L S D E P T H : 1 5 ｍ～3 6 ｍ

OBSERVATION WELLS OF WRA

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SLIDE 5

ON AND AROUND FOCAL REGION OF THE 1999 CHI-CHI ERTHQUAKE

Wen-Chi Lai et.al(2004)

S E I S M I C I N T E N S I T Y ( J M A S C A L E ) 4 ～6

CALUCULATED FROM SEISMIC ACCELERATION DATA USING KAWASUMI’S FORMULA

ALLUVIAL FAN SLOPE OR MOUNTAIN

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SLIDE 6

AQUIFERS

100 50

  • 50
  • 100
  • 150
  • 200
  • 250
  • 300
  • 350

5 10 15 Km 100 50

  • 50
  • 100
  • 150
  • 200
  • 250
  • 300
  • 350

A' A

Layer 1 Layer 2-1 Layer 2-2 Layer 3 Layer 4

Gravel Sand Silt and Mud (Aquitard)

Upper Fan Middle Fan Lower Fan Altitude(m) Altitude(m)

UNCONFINED！

H： V＝1： 100 Wen-Chi Lai et.al

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SLIDE 7

A Q U I F E R S I T U A T I O N N O . O F W E L L S C O S E I S M I C C H A N G E S P E R C A N T A G E ( % ) L A Y E R 1 U N C O N F I N E D 3 9 7 1 8 L A Y E R 2 ( 1 + 2 ) C O N F I N E D 7 8 4 3 5 5 L A Y E R 3 C O N F I N E D 3 8 2 8 7 4 L A Y E R 4 C O N F I N E D 1 3 9 6 9 A L L 1 6 8 8 7 5 2

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SLIDE 8

10000 20000 30000 40000 50000 60000

  • 12
  • 8
  • 4

4 8

Distance of Earthquake Fault (m) Water Level Change (m)

Legend Layer 1 Layer 2-1 Layer 2-2 Layer 3 Layer 4

  • 12
  • 8
  • 4

4 8

Earthquake Fault East Weat Water Level Changes (m)

8 4 4 8

DISTANCE FROM EARTHQUAKE FAULT ( km) West 60 40 20 0 East EARTHQUAKE FAULT ALLUVIAL FAN S L O P E , M O U N T A I N COSEISMIC WATER LEVEL CHANGE (m)

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SLIDE 9

20000 40000 60000

  • 50

50 100 150 200

Distance between observation wells and the earthquake fault (m) Altitude of water table (m)

Earthquake Fault

East West

SEA LEVEL

DROP BY PERMEABILITY ENHANCEMENT

RISE BY LIQUEFACTION

PUMPING

DISTANCE FROM EARTHQUAKE FAULT ( km) West 60 40 20 0 East

200

ALTITUDE OF WATER TABLE (m)

  • 50

100

S L O P E , M O U N T A I N ALLUVIAL FAN V/H～250

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SLIDE 10

MAIN FACTORS FOR EARTHQUAKE-RELATED GROUNDWATER CHANGES VOLUMETRC STRAIN CHANGE SEISMIC GROUND MOTION LIQUEFACTION PERMEABILITY CHANGE Wang et al. (2001) Lai et al.(2004) Lee et al.(2002) Koizumi et al.(2004)

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SLIDE 11

NO COSEISMIC CHAGE SMALL COSEISMIC CHANGE LARGE COSEISMIC CHANGE NO RECOVERY

0 100 200

A C C E L E R A T I O N ( g a l ）

20 10 COUNT

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SLIDE 12

Layer-1 （ UNCONFINED AQUIFER)

0 100 200

A C C E L E R A T I O N ( g a l ）

5 COUNT

NO COSEISMIC CHAGE SMALL COSEISMIC CHANGE LARGE COSEISMIC CHANGE

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SLIDE 13

Layer2（ CONFINED AQUIFER）

0 100 200 10 COUNT

NO COSEISMIC CHAGE SMALL COSEISMIC CHANGE LARGE COSEISMIC CHANGE

A C C E L E R A T I O N ( g a l ）

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SLIDE 14

2 ｍ 1 Y E A R

1日値の変化

D A I L Y V A L U E ( 1 9 9 3

  • 2

)

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SLIDE 15

2 ｍ

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SLIDE 16

EPICENTER DROP RISE

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SLIDE 17

20000 40000 60000

  • 50

50 100 150 200

Distance between observation wells and the earthquake fault (m) Altitude of water table (m)

Earthquake Fault

East West

SEA LEVEL

DROP BY PERMEABILITY ENHANCEMENT

RISE BY LIQUEFACTION

PUMPING

DISTANCE FROM EARTHQUAKE FAULT ( km) West 60 40 20 0 East

200

ALTITUDE OF WATER TABLE (m)

  • 50

100

S L O P E , M O U N T A I N ALLUVIAL FAN V/H～250

GROUND SURFACE

V.D.< 0.2m B O U N D A R Y C O N D I T I O N W A S N O T C H A N G E D P E R M E A B I L I T Y W A S I N I T I A L L Y L A R G E . L O C A L P R E S S U R E C H A N G E W A S D I M I N I S H E D

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SLIDE 18

C O N C L U S I O N S

・W e i n v e s t i g a t e d w a t e r l e v e l c h a n g e s i n t h e 6 6 s t a t i

  • n

s ( 1 6 8 w e l l s )

  • n

a n d a r

  • u

n d t h e f

  • c

a l r e g i

  • n
  • f

t h e 1 9 9 9 C h i

  • C

h i e a r t h q u a k ed u r i n g t h e p e r i

  • d

f r

  • m

1 9 9 3 t

  • 2

. T h e d e p t h s

  • f

t h e w e l l s r a n g e b e t w e e n 1 5 m a n d 3 6 m . ・M

  • s

t

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t h e w e l l w a t e r l e v e l s w h i c h c h a n g e d c

  • s

e i s m i c a l l y r e c

  • v

e r e d b y D e c e m b e r 2 . A l l

  • f

t h e w e l l w a t e r l e v e l s i n t h e a l l u v i a l f a n r e c

  • v

e r d . ・3 w e l l w a t e r l e v e l s , w h i c h d r

  • p

p e d c

  • s

e i s m i c a l l yb y p e r m e a b i l i t y e n h a n c e m e n t , d i d n

  • t

r e c

  • v

e r . T h e y a r e s i t u a t e d i n t h e s l

  • p

e

  • r

m

  • u

n t a i n z

  • n

e s n e a r t h e e a r t h q u a k e f a u l t . ・T h e p

  • s

s i b l e r e a s

  • n

s a r e a s f

  • l

l

  • w

s ; ( 1 ) P e r m e a b i l i t i e so f t h e a q u i f e r s i n t h e a l l u v i a l f a n a r e

  • r

i g i n a l l yl a r g e , ( 2 ) L e v e l s

  • f

n e i g h b

  • r

i n g s e a , r i v e r s a n d l a k e s

  • r

p

  • n

d s , w h i c h a r e i m p

  • r

t a n t b

  • u

n d a r y c

  • n

d i t i

  • n

s c

  • n

t r

  • l

l i n g g r

  • u

n d w a t e r p r e s s u r e s , d i d n

  • t

l a r g e l y c h a n g e a f t e r t h e 1 9 9 9 C h i

  • C

h i e a r t h q u a k e .

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SLIDE 19

A Q U I F E R S I T U A T I O N N O . O F W E L L S C O S E I S M I C C H A N G E S P E R C A N T A G E ( % ) L A Y E R 1 U N C O N F I N E D 3 9 7 1 8 L A Y E R 2 ( 1 + 2 ) C O N F I N E D 7 8 4 3 5 5 L A Y E R 3 C O N F I N E D 3 8 2 8 7 4 L A Y E R 4 C O N F I N E D 1 3 9 6 9 A L L 1 6 8 8 7 5 2

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SLIDE 20

Spatial distribution (P.G.A. and Vol. strain)

  • PGAH
  • Vol. strain

(ppm)

150000 200000 250000 2500000 2550000 2600000 2650000 2700000

100 200 300 400 500 600 700 800 900 1000 1100

# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
  • Volumetric strain