Features of Tsunami height according to type of coastal landforms 2011 Tohoku oki tsunami case

Features of Tsunami height according to type of coastal landforms 2011 Tohoku oki tsunami case (70 Nobuhisa Matta (Disaster Mitigation Research Center Nagoya Univ.) July 3 rd, 2013, at Taipei

Outline + revisit the 2011 Tohoku earthquake and introduce our map + Look at coastal landform classes + compare between Meiji, Showa, and Chile tsunamis + look at simulated runup height patterns of Tsunamis + analysis of 2011 Tohoku tsunami, and importance of bathymetric features Final my conclusion + runup heights of tsunami have a relation to tsunami wave lengths + bathymetric features can help estimate future tsunami wave length

Revisit of the 2011 Tohoku earthquake 2011.3.11

Tsunami inundation and run-up height distribution The 2011 Tohoku Earthquake Tsunami Joint Survey Group

A map of overflow area of the tsunami Before earthquake at Natori (Sendai plain) Purple area - destroyed area Red area - Area covered by tsunami

After earthquake at Natori (Sendai plain) Purple area - Area destroyed area Red area - Area covered by tsunami http://danso.env.nagoya-u.ac.jp/20110311/ecom.html

The map of Natori (Sendai plain) by the Association of Japanese Geographers Purple area - Area destroyed area Red area - Area covered by tsunami http://danso.env.nagoya-u.ac.jp/20110311/ecom.html

Before earthquake at Rikuzentakada (Sanriku ria coast) Purple area - Area destroyed area Red area - Area covered by tsunami

After earthquake at Rikuzentakada (Sanriku ria coast) Purple area - Area destroyed area Red area - Area covered by tsunami

The map of Rikuzentakada (Sanriku ria coast) by Association of Japanese Geographers Papule area is destroyed area Red area is covered by tsunami

Our date Set (for example) Run-up heights in one instance (Hajigami in Kesennuma) High run-up--------low run-up Red point -------- blue point

The features of two tsunami heights data Tsunami Damage Mapping Team, Association of Japanese Geographers findings Interpreted tsunami damage area of the aftermath. - aerial photos stereoscopically Tsunami heights data is Matched by the Digital Elevation Model (DEM) The 2011 Tohoku Earthquake Tsunami Joint Survey Group findings A lot of people measured them in field observations Advantage of this data : similar good quality data throughout hit area, especially on flat surface Defect: not direct observation steeply sloped geography under estimated http://danso.env.nagoya-u.ac.jp/20110311/map/index_e.html Advantage of this data: direct observation steeply sloped geography Defect: observer bias observed time bias, flat surface http://www.coastal.jp/tsunami2011/

Tsunami wave and run-up height distribution The 2011 Tohoku Earthquake Tsunami Joint Survey Group In same latitude, tsunami heights have a variable No. of compailed date In my talk Meiji Sanriku tsunami 140 points showa Sanriku tsunami 188 points Chile tsunami 374 2011 Tohoku tsunami 620 points t

Compared tsunami height distribution between each earthquakes 2011 tsunami is highest since 1896 North latitude South It is difficult to compare detail we target the categories of tsunami height

The classification of the bay type Type form classification The height of showa tsunami On the open ocean (Wide mouth) (Type-1) V-formation Bay 1(Type-1.1) 2030m U-formation Bay 2(Type-1.2) 15 Some coves area 3(Type-1.3) 12 In the gulf (Narrow mouth) (Type-2) V-formation Bay 4(Type-2.1) 15 U-formation Bay 5(Type-2.2) 78m Some coves area 6(Type-2.3) 45m Long gulf (Hei) 23 straight coastline (Tei) 45 Proposal(to(Home(Minister(from(Earthquake(disaster(preven8on(council(()

The classification of the bay type For example Toni Bay (Type-2) Type 1 Yoshihama Bay (Type-1) Okirai Bay (Type-2) Type 1

Distribution of Tsunami height each coastal landscape on Meiji (1896) earthquake m Type-1: Warm color Type-2 cold color Highest type : Type-1.1 North South

Distribution of Tsunami height each coastal landscape on showa (1933) earthquake Type-1: Warm color Type-2 cold color Highest type : Type-1.1 North South

Comparing Meiji with showa tsunami Type-1: Warm color Type-2 cold color Type-1: Warm color Type-2 cold color showa tsunami heights / Meiji tsunami heights showa tsunami height linearly-related North South Meiji tsunami heights / showa tsunami heights Meiji tsunami height Kuji Miyako Trou Kamaishi Kirikiri Rikuzentakada Ofunato Kesennuma Minamisanriku Onagawa Okatsu

Distribution of Tsunami height each coastal landscape on Chile (1960) earthquake m Type-2 > Type-1 Type-1: Warm color Type-2 cold color Trou Kuji North Miyako Kirikiri Kamaishi Ofunato Rikuzentakada Kesennuma Minamisanriku Okatsu Onagawa South

Comparing Meiji with Chile tsunami Chile tsunami Meiji < Chile Kuji Miyako Trou Kamaishi Kirikiri Ofunato Chile tsunami heights / Meiji tsunami heights Rikuzentakada Kesennuma Minamisanriku Onagawa Okatsu North South Meiji tsunami Type-1: Meiji tsunami >>> Chile tsunami Type-2: Meiji Tsunami < Chile tsunami Meiji tsunami heights / Chile tsunami heights

Why is it different pattern between Meiji and Chile? Simulated the relationship between tsunami wave lengths and coastal landforms Narrow tsunami Calculated area Wide tsunami Calculated area purple rectangle are is set initial value as Tsunami

Simulated result The result of the relationship between Tsunami wave length and coastal landform Narrow wave Wide wave Type 2 Type 1 Type 1 Type 2 Type 1 Type-1> Type-2 Type-2> Type-1

That means Topography is tide gauge!! channel Traditional tidal stations have a low sensitivity for common waves and have increased the sensitivity for a tidal wave (long wave). Coastal landforms are varied tide gauge chain.

Compared Joint Survey Group and Association of Japanese Geographers date Tsunami height m 40 Type-1: Warm color Type-2 cold color Joint Survey Group 20 0 North Tsunami height m South 40 Association of Japanese Geographers 20 0 Kuji Miyako Trou Kirikiri Kamaishi Ofunato Kesennuma Minamisanriku Onagawa Okatsu Sakamoto Shiogama Souma

Distribution of Tsunami height each coastal landscape on 2011 Tohoku earthquake Area 1 Area 2 Type-1: Warm color Type-2 cold color Area 3 Souma Sakamoto Shiogama Onagawa Okatsu Minamisanriku Kesennuma Rikuzentakada Ofunato Kamaishi Kirikiri Miyako Trou Kuji Between Miyako and Kamaishi : Type-1 > Type-2 Between Ofunato and Onagawa : Type-1 = Type-2 South of Sakamoto : Type-1 > Type-2

Information of location Kamaishi ( Ofunato( Onagawa( Sendai( Sakamoto ( Tokyo

Comparing Meiji with 2011 Tohoku tsunami Meiji tsunami / 2011 tsunami 2011i tsunami / Meiji tsunami Type-1: Warm color Type-2 cold color Type-1: Warm color Type-2 cold color North South North South Meiji tsunami height at some the Type-1.1 is higher than 2011 tsunami height

Comparing Meiji with 2011tsunami disaggregated by coastal landform 2011 tsunami heights / Meiji tsunami heights Type - 1.1 Type-1.1: north of Kamaishi 2011 >> Meiji South of Ofunato 2011 >= Meiji Onagawa Okatsu Minamisanriku Kesennuma Rikuzentakada Ofunato Kamaishi Kirikiri Miyako Trou Kuji

Pulse wave on wide wave narrow wave (pulse) North Wide wave Kamaishi Pulse wave is not clear South How is this wave generated?

Shallow zone has huge slip created a pulse wave (huge slip model)

Dip changes steeply in the shallow zone created a pulse wave (dip change model) Estimated Tsunami source by active fault on bathymetric feature! Active fault of 450 km in length! tectonic flexible bulgerelative elevation 1000order By Nakata et al. (2012)!! Observed Deformation patten Estimated fault geometry

Simulated two fault models huge slip model Model 1 Fault 2 : huge slip area Fault 1 Dip changes model Model 2 Fault 2-4 : dip is steep Fault 1 Fault 2 Fault 2 Fault 3 Faultdip15slip15m shallow Faultdip15Slip 20 Fault 4 Faultdip15slip15m shallow in 5 km Fault,4 dip45slip 15 Fault 3 dip15slip 15

On simulation results, both Models can explain the tsunami height phenomenon (Type1 >> Type 2 north of Kamaishi) Huge slip Model can not calculate the tsunami height phenomenon (Type1 = Type 2 south of Ofunato) Huge slip Model Type1> Type2 Yamada Kamaishi Ofunato South of Ofunato Rikuzentakada Kesennnuma Minamisanriku Type1> Type2 Dip changed model Yamada Type1> Type2 Kamaishi Ofunato South of Ofunato Rikuzentakada Kesennnuma Minamisanriku Type1 = Type 2

Simulated results of tsunami heights by Nakata san group By Muroi et al., 2012 Nakata%model Yagi%modelobservation

What happen in Fukushima Open sea area has huge tsunami height Souma Drop!! Huge tsunami height At the Inland, tsunami height is not so high the reason is narrow tsunami can not go to the inland Type 1? > Type 2?

Active fault on see bed Tectonic bulge Tectonic bulge 100%km

Result! Coastal landforms are a sensor for tsunami features.! wide wave: Type2 > Type 1! narrow wave : Type1 > Type 2! 2011 earthquake need not have huge slip.! 2011 tsunami features are explainable by tectonic geomorphology on sea bottoms In conclusion my recommendation is to include the geomorphological methods when I am discussed today in studying tsunami height.

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