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

6 Are a s o f T L S surve ys in T o ho ku 140 ° E 130 ° E 40 ° N Ane yo shi 30 ° N T o kura Yo shiha ma Oina mi Og a tsu N

360 ° T L S Surve ys using GL S-1500(R) ± 35 ° • T o pc o n Co ., T o 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 )

Eroded ridge in Tokura

T o kura 01 (m) (m) Be dro c k e ro sio n Be dro c k e ro sio n (Artific ia l c ut) (m) No rth-fa c ing slo pe So uth-fa c ing slo pe

10 Re pe a te d tsuna mis a lo ng 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 ) the Sa nriku c o a st 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 o 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 6 he ig hts a nd ste p-like 7 fe a ture s (m) 6 7 (m) Run-up Run-up I nunda tio n I nunda tio n W NE SW E (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 Ge ntle Ste e p I nunda tio n N S Lines 6.5 – 9

L o ng itudina l pro file s o f va lle ys in Ane yo shi fro m AL S DE M Ane yo shi va lle y K nic kpo int Elevation (m) No rthe rn va lle y Distance (m)

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 • 2 ] A : Dra ina g e a re a [L -1 ] • P : Me a n a nnua l pre c ipita tio n [L T • 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 ] • • -1 T -2 ] S c : Unc o nfine d c o mpre ssive stre ng th [ML

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 c = 111.2 MPa (  Sc hmidt R – S 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)