Flow dynamics/morphological impacts of the 2011 off the Pacific - - PowerPoint PPT Presentation

Flow dynamics/morphological impacts of the 2011 off the Pacific coast of Tohoku Earthquake Tsunami, Japan

• T. Oguchi, Y.S. Hayakawa,
• H. Saito, Univ. Tokyo
• V. R. Baker, Univ. Arizona

The 3.11 Tsunami

Victor Baker Specialist of landforms created by megafloods Tsunamis this time

Sendai Plain, July 2011

Aneyoshi, Sanriku

Are a s o f T L S surve ys in T

• ho ku

6

Ane yo shi Og a tsu T

• kura

Yo shiha ma

N

Oina mi

130°E 140°E 40°N 30°N

T L S Surve ys using GL S-1500(R)

• T
• pc o n Co ., T
• kyo
• Me a sure spe e d

– 30,000 po ints/ se c

• Ac c ura c ie s

– Dista nc e : 4 mm @ 150 m – Ang le : 6”

• Ma ximum dista nc e

– 500 m (90% re fle c ta nc e )

±35°

360°

Eroded ridge in Tokura

T

• kura 01

No rth-fa c ing slo pe So uth-fa c ing slo pe Be dro c k e ro sio n Be dro c k e ro sio n (Artific ia l c ut)

(m) (m) (m)

Re pe a te d tsuna mis a lo ng the Sa nriku c o a st

10

http:/ / o utre a c h.e ri.u-to kyo .a c .jp/ e q vo lc / 201103_to ho ku/ e ng

(b y T suji, E a rthq ua ke Re se a rc h Institute )

Blue = 1896 Me iji-Sa nriku e a rthq ua ke L ig ht g re e n= 1933 Sa nriku e a rthq ua ke Da rk g re e n= 1960 Gre a t Chile a n E a rthq ua ke Blue -g ra y= 2010 Chile e a rthq ua ke Re d= 2011 T

• ho ku E

a rthq ua ke

Va lle y in Ane yo shi

3D vie w o f po int c lo ud (RGB c o lo re d) with re mo ve d po ints

Numb e r o f po ints me a sure d: 7,342,548 Numb e r o f po ints a fte r c le a ning : 6,507,913

Me a n po int de nsity: 39.97 pts/ m 2

 e q uiva le nt to 0.16 m (±0.09 m in s.d.) fo r e a c h po int  20 c m c e ll size DE

M

Ana lyse s o n a T I N-de rive d 20-c m DE M

Na rro w Wide

T suna mi inunda tio n/ run-up he ig hts a nd ste p-like fe a ture s

6 7 6 7

Run-up I nunda tio n I nunda tio n Run-up

E W NE SW (m) (m) (m) (m)

“I nve rse ” a symme try a t a me a nde r b e nd

– I nne r slo pe : ste e p, o ute r slo pe : g e ntle

Lines 6.5 – 9

Ste e p Ge ntle

I nunda tio n N S

L

• ng itudina l pro file s o f va lle ys in

Ane yo shi fro m AL S DE M

Distance (m) Elevation (m)

Ane yo shi va lle y No rthe rn va lle y K nic kpo int

An e mpiric a l mo de l to pre dic t knic k- po int re tre a t ra te b y rive r e ro sio n (Ha ya ka wa e t a l.)

• E

: re c e ssio n ra te o f a knic kpo int

• A: Dra ina g e a re a [L

2]

• P: Me a n a nnua l pre c ipita tio n [L

T

• 1]
• W: Width o f knic kpo int [L

]

• H: He ig ht o f knic kpo int [L

]

• ρ: Wa te r de nsity [ML
• 3]
• S

c : Unc o nfine d c o mpre ssive stre ng th [ML

• 1T
• 2]

Pre dic te d e ro sio n ra te o f the knic kpo int

• Pa ra me te rs me a sure d

– A = 1.0 km 2 – P = 1300 mm/ y – W = 4 m – H = 10 m – S

c = 111.2 MPa ( Sc hmidt R N = 53.8%)

• E

stima te d re c e ssio n ra te o f the knic kpo int: 0.0095 m/ y (= c . 1 c m/ y)

– Ve ry slo w, ne e ds 10,000 ye a rs to re c e de 100 m – E

nha nc e d e ro sio n b y tsuna mi wa ve s is fe a sib le

5-m Airborne Lidar DEM Flow Simulation (FLO-2D) (Univ. Arizona)

Survey in the Ki’i Peninsula

Tsunami- transported boulders TLS data Kushimoto Town Airborne Lidar

Concluding remarks

 TLS surveys – detection of very detailed topography that may reflect accumulated tsunami erosion  Rough but relatively fast prediction of tsunami magnitude from topography (cf. finding ancient tsunami deposits)