Coastal Engineering Journal, Vol. 58, No. 4 (2016) (18 pages) c The Author(s) DOI: /S

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1 Coastal Engineering Journal, Vol. 58, No. 4 (2016) (18 pages) c The Author(s) DOI: /S Tsunami Simulation by 3D Model Around a Power Station Due to the 2011 Tohoku Earthquake Rikuma Shijo,, Yoshiaki Tsukuda, Toshihiro Sato, Kojiro Higuchi, Satoshi Kudo,JunichiIshizaki, Shinichi Shimizu and Hajime Mase Nagasaki Research and Development Center Technology and Innovation Headquarters, Mitsubishi Heavy Industries, Ltd, , Fukahori-Machi, Nagasaki , Japan Takasago Machinery Works, Mitsubishi Heavy Industries, Ltd, 1-1 Shinhama, 2-Chome, Arai-cho, Takasago City, Hyogo , Japan Takasago Research and Development Center Technology and Innovation Headquarters, Mitsubishi Heavy Industries, Ltd, 1-1 Shinhama, 2-Chome, Arai-cho, Takasago City, Hyogo , Japan Tohoku Electric Power Co., Inc., Honcho, Aoba-ku, Sendai, Miyagi , Japan Haramachi Thermal Power Station, Tohoku Electric Power Co., Inc., 54 Ofunasako, Kanazawa-aza, Haramachi-ku, Minamisoma City, Fukushima , Japan Tohoku Electric Power Co., Inc., Honcho, Aoba-ku, Sendai, Miyagi , Japan Haramachi Thermal Power Station, Tohoku Electric Power Co., Inc., 54 Ofunasako, Kanazawa-aza, Haramachi-ku, Minamisoma City, Fukushima , Japan Coastal Disasters Research Section, Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, Kyoto , Japan rikuma shijo@mhi.co.jp This is an Open Access article published by World Scientific Publishing Company. It is distributed under the terms of the Creative Commons Attribution 4.0 (CC-BY) License. Further distribution of this work is permitted, provided the original work is properly cited

2 R. Shijo et al. Received 8 August 2015 Accepted 2 September 2016 Published 25 October 2016 In the 2011 Tohoku Earthquake, many structures were destroyed by the tsunami whose magnitudes were much larger than the design level. Tsunami defense structures in coastal areas will need reinforcement in the future, and for that reason it is important to evaluate tsunami behavior and resulting tsunami force. This study analyzes tsunami transformation around a Haramachi thermal power station which suffered serious damage by the tsunami due to the 2011 Tohoku Earthquake and which has complex topography and building layout. A three-dimensional (3D) tsunami simulation is carried out for a surrounding region of the Haramachi thermal power station using boundary conditions of the water surface elevation and flow velocity obtained from a two-dimensional (2D) tsunami simulation by a nonlinear shallow water model. Using these boundary conditions, the computer fluid dynamic model FLUENT is employed to simulate the tsunami behavior around the Haramachi thermal power station. The validity of the predictions is examined by comparison with actual traces of tsunami inundation depths (I.D.). Keywords: Three-dimensional tsunami simulation; VOF model; tsunami behavior; tsunami inundation. 1. Introduction In the 2011 Tohoku Earthquake, many structures were destroyed by tsunamis whose magnitudes were much larger than the design level. Overview of damage to coastal structures is summarized in Mori et al. [2013] and Mase et al. [2013]. Since the occurrence probability of the Tokai, Tonankai and Nankai Earthquake is expected to be as high as 60 70% within 30 years [Headquarters for Earthquake Research Promotion, 2012], we should prepare appropriately for tsunamis. In preparation for tsunami inundation, it is important to evaluate tsunami behavior and resulting tsunami forces in coastal areas. The nonlinear shallow water model is generally used to simulate tsunami behavior where existing structures are modeled as either bottom surface roughness or stepped topography [Imamura et al., 1988]. However, since tsunami propagation on land is highly influenced by topography and structures, detailed simulation of tsunami is required to reproduce reflection, diffraction and velocities around structures. Ikesue et al. [2012] and Shijo et al. [2013] simulated tsunami transformations and tsunami forces acting on buildings using ANSYS FLUENT [ANSYS, 2014], which is a general-purpose fluid analysis code with easier computation grid setting and the volume of fluid (VOF) method [Hirt and Nichols, 1981]. FLUENT is applicable to the case of tsunami inundation over complex terrain. This study analyzes the tsunami transformation by FLUENT around the Haramachi thermal power station where topography and building layout are complex. The validity of the predictions is examined by comparison with actual traces of tsunami inundation depths (I.D.). Since it is inefficient to conduct a threedimensional (3D) calculation from the offshore region to the Haramachi thermal

3 Tsunami Simulation by 3D Model power station, a 3D simulation is applied only to a surrounding region of the station. A two-dimensional (2D) nonlinear shallow water model is used to provide the boundary conditions of water surface elevation and flow velocity for the smaller region where the 3D simulation is carried out. 2. Overview of Damages in the Haramachi Power Station At 14:46 JST on 11 March 2011, a massive earthquake occurred off the pacific coast of Tohoku, Japan, causing enormous tsunamis which devastated the Japanese northeast coast. Figure 1 shows the Tohoku district, the location of the epicenter, and the GPS buoys. The Haramachi thermal power station, operated by Tohoku Electric Power and located at ( N, E) as shown in Fig. 1, was one of the areas worst hit by the tsunami. Figure 2 is an aerial photograph of Haramachi thermal power station before the earthquake. This figure also indicates the I.D. at buildings where clear traces were left; the I.D. were defined as the water depth above the local ground level whose height was T. P. +5 m (T. P. is the datum of altitude in Japan). The I.D. were measured by the fifth, sixth, and seventh authors with a laser range finder on 13 June It is seen from Fig. 2 that a 15.3 m I.D. was measured at a coal ash storage tank installed near a south seawall and labeled No. 1. The I.D. (a) Iwate Pref. Central ( N, E) (b) Iwate Pref. South ( N, E) Epicenter ( N, E) Haramachi thermal power station (37.666ºN, ºE) (c) Fukushima Pref. ( N, E) : GPS Buoy Fig. 1. Location of Haramachi thermal power station, GPS buoys and epicenter

4 R. Shijo et al. No.6 (Sampling build.) I.D.= 8.99 m North No.4 (Electrostatic precipitator) I.D.= m No.5 (Observation build.) I.D.= 9.51 m (c) (e) No.4 No.2 (Ash disposal build.) I.D.= m South (f) (a) No.3 (Service build.) I.D.= m (b) No.1 (Coal ash storage tank) I.D.= m No.1 No.2 No.3 (d) Unloading cranes Fig. 2. Aerial photograph before the earthquake and measured I.D. at buildings. North South Running up from the south shore (a) Service building. (b) Wave dissipating block. Fig. 3. Damage in the Haramachi thermal power station (Locations of figures are shown in Fig. 2). measurements decrease to the north of the site to 8.99 m at a sampling building labeled No. 6. Figures 3(a) 3(f) show damage to buildings, machines, and storage tanks in this power station [Tohoku Electric Power Co., Inc., 2013]. The locations of figures (a) (f) are shown in Fig. 2 using the same labels. The eyewitness accounts of the staff who evacuated on the fifth floor of the service building and the recorded video reported that main structures shown in Fig. 3 were damaged by the tsunami-induced

5 Tsunami Simulation by 3D Model No.4 No.3 (c) Large fan. (d) Unloading cranes. (e) Inside of turbine building. Sliding Fig. 3. (Continued) (f) Storage tank. inundation not by the seismic. Figure 3(a) shows a service building where tsunami flooding reached the third floor and destroyed walls and windows. When the tsunami inundated the Haramachi thermal power station, staff evacuated on the fifth floor of the service building and recorded the tsunami flooding all over the station for two minutes using a video recorder. These staff reported that the ground surface in the station was slowly flooded by the first tsunami wave, and the second tsunami wave inundated at 15:38 with a sudden water level rise first from the south breakwater then from the front of unloading cranes to the east; thus, the Haramachi thermal power station was hit by tsunami inundation from two directions [Koizumi et al., 2012]. Additional evidence that the tsunami moved from the south breakwater is the land run-up of a wave dissipating block located on the south shore (shown in Fig. 3(b)) and the northward displacement of a large fan (shown in Fig. 3(c)). The large fan was damaged and carried away by the tsunami-induced inundation from the south after floating due to its buoyancy. Furthermore, the reduction of I.D. toward the north also indicates that the tsunami flooded over the Haramachi thermal power station from the south to the north with reducing momentum. Two unloading cranes collapsed to the west direction (as shown in Fig. 3(d)) indicating that a tsunami approached the station from the east. Four cranes were

6 R. Shijo et al. set at the location indicated in Fig. 2(d), labeled No. 1 4 from south to north. After the seismic hazard, cranes No. 1 and No. 2 remained with less damage, and cranes No. 3 and No. 4 were destroyed and fell into the sea (shown in Fig. 3(d)). Damage to cranes No. 1 and No. 2 was relatively small because a coal transport ship was anchored in front of them acting as a barrier to the tsunami. Equipment and pipes inside of the turbine building were destroyed and dispersed (shown as Fig. 3(e)). Tanks suffered various kinds of damage such as sliding (shown in Fig. 3(f)), buckling, and dispersed. The type of damage to the tanks depended on the size and content amount. A coal ash storage tank located near the south seawall had small damage due to the resistant strength of its reinforced concrete structure, despite being located in the most upstream side of the tsunami with the maximum I.D. of the entire station. 3. Simulation of Tsunami Behavior It is important to evaluate the tsunami behavior and tsunami force of future tsunamis for hazard mitigation. It will be necessary to use 3D numerical tsunami simulations that can deal with the effects of existing coastal structures and buildings as well as detailed bathymetry and topography. Choi et al. [2008] used a 3D numerical simulation to study fluid behavior in the Imwon Port in Korea caused by tsunami due to the 1983 Sea of Japan Earthquake using a 3D numerical simulation. However, their study did not consider the existence of coastal structures on land since they focused only on the flow behavior in the port. The present study analyzes tsunami behavior around the Haramachi thermal power station using a 3D simulation under complex topography and building layout. The applicability of the simulation is verified by comparison of the predictions with observations Tsunami propagation from ocean to coast Calculation method First a large-scale numerical simulation was conducted for the entire Tohoku area to obtain boundary conditions for a detailed tsunami simulation around the Haramachi thermal power station. In this study, different modifications of well-known tsunami propagation model TUNAMI-N2 [Goto et al., 1997] were used to simulate tsunami propagation. The governing equations for this model are the so called nonlinear shallow water equations: η t + M x + N =0, (1) y M t + x ( M 2 D ) + y ( MN D ) + gd η x + gn2 D 7 / 3 M M 2 + N 2 =0, (2)

7 Tsunami Simulation by 3D Model N t + ( ) MN + x D y ( N 2 D ) + gd η y + gn2 N M 2 + N 2 =0, (3) D 7 / 3 where t is the time, x and y are the horizontal coordinates, η is the vertical displacement of water surface above the still water level, M and N are the fluxes in the x and y directions respectively, h is the still water depth, D is the total water depth (= h+η), g is the gravitational acceleration, and n is the Manning s roughness. Manning s roughness is usually chosen as a constant for a given sea bottom condition [Imamura et al., 2006]. The authors perform a simulation using the constant value n = assuming the natural channels are in good condition. Equations (1) (3) are solved on staggered grids using the leap-frog method. The calculation domain spans from 35 Nto41 N in latitude (about 670 km) and from 140 E to 145 E in longitude (about 460 km). Land elevation data was obtained from the Geospatial Information Authority of Japan GSI [2015] and water depth data was obtained from J-EGG500 of the Japan Oceanographic Data Center JODAC [2015]. As the fault model the authors selected the Fujii and Satake [2011] Ver. 4.2 model. The earth crust displacement was determined by Mansinha and Smylie [1971], and this displacement was used as the initial distribution of the water surface elevation. The mesh size used is 1,350 m and the time step is 1 s. The duration of the simulation was 2 h Simulation results Figure 4 shows the spatial distributions of water surface elevation after 10, 30, 50 and 60 min from the occurrence of the earthquake. The tsunami starts to propagate concentrically immediately after the earthquake; it arrives at coastal area of Iwate Prefecture after 30 min then hits the power station after 50 min from the occurrence of earthquake. Figure 5 compares the simulated water surface elevations with the observed data of the Nationwide Ocean Wave Information Network for Ports and Harbors (NOWPHAS) [Port and Airport Research Institute, 2011]. Simulated and observed water surface elevations agree fairly well for the arrival times and maximum tsunami wave heights Three-dimensional tsunami simulation around the Haramachi thermal power station Calculation method A 3D tsunami simulation based on FLUENT was carried out to study tsunami behavior and I.D. in the Haramachi thermal power station. FLUENT is a generalpurpose fluid analysis code with easier computation grid setting of orthogonal mesh and unstructured mesh and it has functions to solve compressible flow, incompressible flow, laminar flow, and turbulent flow based on the finite volume method. The

8 R. Shijo et al. After 10 minutes After 30 minutes About 670km Haramachi thermal power station Haramachi thermal power station About 460km After 50 minutes Haramachi thermal power station After 60 minutes Haramachi thermal power station Water elevation [m] Fig. 4. Numerical results from 2D tsunami simulation. water surface elevation is determined by the VOF method [Hirt and Nichols, 1981]. The governing equations used in this model are the 3D Navier Stokes equations: ρ + (ρu) =0, (4) t (ρu) + (ρuu) = p + µ ( u)+ρg, (5) t ρ = φρ 1 +(1 φ)ρ 2, (6)

9 Tsunami Simulation by 3D Model (c) Fukushima Pref. : GPS Point (a) Iwate Pref. Central (b) Iwate Pref. South Haramachi thermal power station Water elevation (m) Water elevation (m) Water elevation (m) (a) Offshore of Iwate Pref. Central 12 GPS observation 10 Simulation :40 14:50 15:00 15:10 15:20 15:30 15:40 Time (JST) (b) Offshore of Iwate Pref. South 14:40 14:50 15:00 15:10 15:20 15:30 15:40 Time (JST) (c) Offshore of Fukushima Pref. GPS observation Simulation GPS observation Simulation 14:40 14:50 15:00 15:10 15:20 15:30 15:40 Time (JST) Fig. 5. Time history of offshore tsunami wave profile. where u is the velocity vector; p is the pressure; µ is the fluid viscosity; g is the gravitational acceleration vector; ρ 1 is the fluid density; ρ 2 is the air density; φ is the volume ratio of fluid (VOF function) given by 1 for fluid, 0 for air and 0.5 at the free surface; and ρ is the apparent density considering the mix of fluid and air. The finite volume method was used for the discretization of the governing Eqs. (4) and (5), and the pressure-implicit with splitting of operators PISO method [Issa, 1986] was adopted for the coupled analysis of flow velocity and pressure. The VOF method accurately tracks the sharp interface and does not compute the dynamics in the void or air regions. In each mesh, the sum of volume fraction of fluid and air is unity. The apparent density, expressed by Eq. (6), of all meshes in the calculation region is either purely representative of one of the phases, or representative of a mixture of the phases, depending upon the volume fraction value which varies in time greatly during tsunami flooding. The target area of the present simulation is a rectangular domain containing the power station with dimensions 3.5 km (east west) by 3.0 km (north south) shown by the solid red lines in Fig. 6. Figure 7 shows the water surface elevation as simulated by TUNAMI-N2 at the reference point indicated by the black triangle in Fig. 6. After the first tsunami wave

10 R. Shijo et al. N 3.0km 2.0km Reference point of water surface eleva on and velocity 3.5km Fig. 6. Simulation area and a reference point of water surface elevation and velocity (GSI Authority of Japan). Water surface elevation (m) 2km offshore of the power station Second wave First wave :40 14:50 15:00 15:10 15:20 15:30 15:40 15:50 16:00 16:10 Time (JST) Fig. 7. Water surface elevation at the reference point shown in Fig. 6. rising slowly from 15:20 to 15:36, the water surface rose remarkably from 15:36 to 15:42. As mentioned in Sec. 2, a video recording indicates the tsunami inundated the power station twice and the second tsunami runup arrived at 15:38. The 3D simulation was carried out for the behavior of the second tsunami wave from 15:35 to 15:50. Figure 8 shows the boundary condition time series of water surface elevation, flow velocity, and direction at the reference point. These boundary conditions were applied to all meshes facing the ocean, and a free transmission condition was given to all boundary meshes. Specifically, the water surface elevation and flow velocity at 15:35 were provided as initial values to all ocean meshes then after the beginning of 3D simulation, both water surface elevation and flow velocity from 15:35 to 15:50 were given every 0.05 s to all meshes facing the ocean. Water surface level and flow velocity of each mesh of each time step was computed by carrying out a convergence calculation at each time step

11 Tsunami Simulation by 3D Model 12 water surface elevation tsunami direction water velocity 180 Water surface elevation (m) Water velocity (m/s) :35 15:40 15:45 15:50 Time (JST) Tsunami direction (deg) Fig. 8. Boundary conditions at the reference point in Fig. 6 for the 3D tsunami simulation. Figure 9 displays the configuration of the calculation domain with reproduced buildings and tanks in the station, as well as breakwaters and the coal transport ship anchored in front of two southern-most unloading cranes on the south side at the time of tsunami disaster. Land elevation data was based on GSI data, and sea depth was obtained from J-EGG500 of JODAC and from a contour line table around the 3km Topography Structures South seawall North seawall Bathymetry N 3.5km Tanks Boiler/Turbine building Unloading cranes Coal ship Fig. 9. 3D view of calculation region

12 R. Shijo et al. Fig D fine mesh for simulation. 0.5m/mesh Haramachi thermal power station. Structure shapes were modeled from drawings of the station. Figure 10 shows the fine mesh with 0.5 m uniform lattice grids in the area around the buildings. The grid intervals were increased with distance from the buildings up to 5 m to relieve the computational load. The turbulent model used in the simulation is the Large-Eddy Simulation (LES) [Smagorinsky, 1963] and the sub-grid model of LES is the Smagorinsky [1963] model. In this study, these models were used without doing any form of sensitivity analysis. Because a review of the previous study [Shijo et al., 2012] indicates that adapting LES as the turbulent model and using the mesh dividing around the building into 20 in its height direction were found to be most accurate. The total number of mesh is 12 million and simulation was done by parallel computation. In this case approximately 90 h of wall clock time are needed for 15 min simulation using 24 CPUs Simulation results Figure 11 shows snapshots of water surface elevations. A volume ratio of fluid, φ, in each mesh was calculated; φ =1.0, 0.0 and 0.5 were thought to be fluid phase, air

13 Tsunami Simulation by 3D Model South North (a) Tsunami propagation (15:38). South South (b) Running up from the south seawall (15:40). North North (c) Acting on tanks and running up from the front of unloading cranes (15:42). Fig. 11. Simulated tsunami behavior around the Haramachi thermal power station

14 R. Shijo et al. South North (d) Running up to the entire site (15:44). Fig. 11. (Continued) phase, and free surface, respectively. The water surface shown in Fig. 11 was drawn by connecting the coordinates of φ =0.5. First, the tsunami invades the area, as shown in Fig. 11(a), and runs up the power station from the south seawall, as shown in Fig. 11(b). Then, the tsunami struck the storage tanks from the south, and reached the unloading cranes from No. 4 No. 2 No. 3 No. 6 No. 5 North No. 1 Maximum inundation depth (m) Aerial photograph before the earthquake On-site trace Simulation No. 6 No. 5 No. 4 No. 3 No. 2 No. 1 Fig. 12. Comparison between observed and simulated I.D

15 Tsunami Simulation by 3D Model flow velocity(m/s) North Service build. South Fig. 13. Flow velocity distribution in the Haramachi thermal power station

16 R. Shijo et al. the east as shown in Fig. 11(c). Figure 11(d) indicates flooding over the Haramachi thermal power station from the two directions. As mentioned in Sec. 2, the eyewitness accounts of the staff who evacuated on the fifth floor of the service building and the recorded video both agree with the simulated results of Fig. 11 showing that the power station was hit by the tsunami from two directions Tsunami inundation depths Figure 12 compares the observed I.D. from on-site traces with the simulated results. The observed I.D. tend to decrease toward the north, and this tendency was also reproduced in the predictions. Although, the I.D. of each building tends to be overestimated in the simulation, the errors between the observations and simulations are within 15%. The reason for this overestimating of the I.D. is that simulation model deals wall as a filled surface despite a window-pane and a wall of the building actually fall out by the collision of tsunami-induced inundation. Figure 13 indicates flow velocity vectors at the water surface in the Haramachi thermal power station at the time of maximum I.D. around the service building. The tsunami propagated from the south to the north through the station. The flow velocities in the red area in the figure are faster than those in other areas by about 11 m/s due to the effect of contraction by surrounding structures. The detailed analysis of local flow is also one of the features of the 3D numerical simulation. 4. Conclusions This study analyzed the tsunami transformation around the complex topography and building layout of the Haramachi thermal power station, which suffered serious damage by tsunami due to the 2011 Tohoku Earthquake. A 3D simulation was carried out for a surrounding region of the Haramachi thermal power station using boundary conditions of the water surface elevation and flow velocity obtained from a 2D tsunami simulation by a nonlinear shallow water model. The validity of the predictions was examined by comparison with actual traces of tsunami I.D. The main results are as follows: (1) The tsunami simulation revealed that an initial tsunami wave caused a slow water surface level rise and was followed by a second tsunami wave which caused a remarkable rise in water surface elevation from 15:36 to 15:42 and flooded over the Haramachi thermal power station. (2) Eyewitness accounts of staff who evacuated on the fifth floor of the service building as well as recorded video agreed with the simulated results showing that the power station was hit by the tsunami from two directions. (3) The observed I.D. at buildings in the Haramachi thermal power station were reproduced by the present 3D tsunami simulation within 15% errors

17 Tsunami Simulation by 3D Model The feature of the 3D simulation is able to evaluate tsunami wave force acting on a structure directly except the collision force of drifting objects. Further simulation studies are underway to take into account the comparison between the tsunami wave force acting on the structures and damage of them. The results of these studies will be reported soon. References ANSYS [2014] ANSYS Fluent, Choi, B. H., Pelinovsky, E., Kim, D. C., Kim, K. O. & Kim, K. H. [2008] Three-dimensional simulation of the 1983 central East (Japan) Sea earthquake tsunami at the Imwon Port (Korea), J. Ocean Eng. 35, Fujii, Y. & Satake, K. [2011] Tsunami wave source of the 2011 off the Pacific coast of Tohoku Earthquake (provisional result, Ver. 4.2 and Ver. 4.6), fujii/offtohokupacific2011/tsunami ja ver4.2and4.6.html. Geospatial Information Authority of Japan [2015] GIS toha, whatisgis.html (in Japanese). Goto, C., Ogawa, Y., Shuto, N. & Imamura, F. [1997] Numerical method of tsunami simulation with the leap-frog scheme (IUGG/IOC Time Project), IOC Manual, UNESCO, Report No. 35. Headquarters for Earthquake Research Promotion [2012] Overview of long-term evaluation of subduction earthquakes, (in Japanese). Hirt, C. W. & Nichols, B. D. [1981] Volume of fluid (VOF) method for the dynamics of free boundaries, J. Comput. Phys. 39, Ikesue, S., Shijo, R. & Sato, T. [2012] 3D-simulation of tsunami wave force on multiple structures, Ann. Rep. Jpn. Soc. Civ. Eng. 2, 216 (in Japanese). Imamura, F., Shuto, N. & Goto, C. [1988] Numerical simulations of the transoceanic propagation of tsunamis, in Proc. 6th Congress APD-IAHR, (Int. Assoc. for Hydro. Envir. Eng. and Res., Kyoto, Japan), Imamura, F., Yalciner, A. C. & Ozyurt, G. [2006] Tsunami modelling manual, org/ptws/21/documents/tsumodelman-v3-imamurayalcinerozyurtpr06.pdf. Issa, R. I. [1986] Solution of the implicitly discretised fluid flow equations by operator-splitting, J. Comput. Phys. 62, Japan Oceanographic Data Center [2015] 500 m mesh sea depth data, go.jp/vpage/depth500 file j.html (in Japanese). Koizumi, Y., Asano, H. & Okawa, T. [2012] Damages of energy infrastructure in the research committee for the urgent surveys of the East Japan Great-Earthquake, J. Ato. Energy Soc. Jpn. 54(12), (in Japanese). Mansinha, L. & Smylie, D. E. [1971] The displacement fields of inclined faults, Bull. Seismol. Soc. Am. 61, Mase, H., Kimura, Y., Yamakawa, Y., Yasuda, T., Mori, N. & Cox, D. [2013] Were coastal defensive structures completely broken by an unexpectedly large tsunami? A field survey, Earthq. Spectra 29(S1), S145 S160, doi: / Mori, N., Cox, D., Yasuda, T. & Mase, H. [2013] Overview of the 2011 Tohoku earthquake tsunami damage and its relation to coastal protection along the Sanriku Coast, Earthq. Spectra 29(S1), S127 S143, doi: / Port and Airport Research Institute [2011] Urgent survey for 2011 Great East Japan Earthquake and tsunami disaster in ports and coasts, Technical Note of the Port and Airport Research Institute, Report Nos. 1231, 238 p. (in Japanese). Shijo, R., Sato, T. & Ikesue, S. [2012] 3D-Simulation of tsunami wave force on multiple structures, J. Jpn. Soc. Civ. Eng. B2 (Coastal Eng.) 68(2), I (in Japanese)

18 R. Shijo et al. Shijo, R., Tsukuda, Y., Sato, T., Higuchi, K., Kudo, S., Ishizaki, J. & Shimizu, S. (2013), 3D simulation of tsunami caused by Tohoku-Pacific Ocean Earthquake in the power plant, in Proc. 90th Japan Society of Mechanical Engineers Fluidics Section Lecture (JSME, Tokyo, Japan), (in Japanese). Smagorinsky, J. [1963] General circulation experiments with the primitive equations I. The basic experiment, Mon. Weather Rev. 91, Tohoku Electric Power Co., Inc. [2013] Damages in the power station, p 04.pdf