TSUNAMI DAMAGE ASSESSMENT ON ROAD STRUCTURES IN THE 2011 OFF THE PACIFIC COAST OF TOHOKU EARTHQUAKE

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1 Proceedings of the International Symposium on Engineering Lessons Learned from the 211 Great East Japan Earthquake, March 1-, 212, Tokyo, Japan TSUNAMI DAMAGE ASSESSMENT ON ROAD STRUCTURES IN THE 211 OFF THE PACIFIC COAST OF TOHOKU EARTHQUAKE Gaku SHOJI 1, Tomoharu NAKAMURA 2 and Kazunori TAKAHASHI 3 1 Associate Professor, Faculty of Engineering, Information and Systems, University of Tsukua, Iaraki, Japan, gshoji@kz.tsukua.ac.jp 2 College of Engineering Systems, University of Tsukua, Iaraki, Japan, s811237@u.tsukua.ac.jp 3 Graduate Student, Graduate School of Systems and Information Engineering, University of Tsukua, Iaraki, Japan, s112951@u.tsukua.ac.jp ABSTRACT: We assess the tsunami damage on road structures due to the 211 off the Pacific Coast of Tohoku earthquake tsunami. The damage on national roads and expressways at thirteen prefectures of Tohoku and Kanto regions, and the damage on prefectural roads at five prefectures of Tohoku regions are assessed. For related 12 data, we analyzed the damage modes due to tsunami wave loads, and clarified damage ratio R N defined y the value of numer of ridge damage points N d divided y total numer of exposed ridges N t, focusing on wash-away ridges. Key Words: The 211 off the Pacific Coast of Tohoku earthquake tsunami, road structure, ridge, tsunami damage INTRODUCTION In the 211 off the Pacific Coast of Tohoku earthquake Mw=9.) on March 11, 211JMA 211), extensive damage of road structures located at Tohoku areas such as Iwate, Miyagi and Fukushima prefectures occurred due to the tsunamis. We collect 12 damage data of road structures due to the tsunamis opened at the related we sites for analyses and classify 29 failure modes. For damage assessment of ridges, we otain the inundation heights at damaged ridges due to the tsunamis y series of tsunami flow simulation ased on shallow water theory, which are discretized y using the finite difference method with a staggered leap-flog scheme DCRC 29). Finally, we calculate damage ratio R N dependent on an inundation height, which is defined y the value of numer of ridge damage points N d divided y total numer of exposed ridges N t, focusing on wash-away ridges. 1711

2 Road Management Sectors Tale 1 Analyzed data of damaged road structures Damage Information URL) Road Management Sectors Damage Information URL) Main Office Disasiter Prevention Imformation Press Release) Earthquake Imformation 15th Version) hou111.htm Road Damage Information in the 211 off the Pacific Coast of Tohoku Earthquake 1st and 3rd Versions) Omiya National Road Office Iwate River and National Road Office Earthquake Imformation : Iwate River and National Road Office 2nd and 3rd Versions) Shuto National Road Office Damage of National Road No :5 on March 11) Sanriku National Road Office Sanriku National Road Office Earthquake Imformation 2nd Version) Yokohama National Road Office Damage Imformation in the 211 off the Pacific Coast of Tohoku Earthquake 3rd Version) Sendai River and National Road Office Disasiter Prevention Imformation Press Release) Sendai River and National Road Office Disaster Information 3rd, 13th, and 1th Versions) Aomori Prefecture Disaster Countermeasures Office Aout the Damage in the 211 off the Pacific Coast of Tohoku Earthquake 3th Version) Yamagata River and National Road Office Disasiter Prevention Imformation Yamagata River and National Road Office Earthquake Imformation 3rd, th, 6th, and 7th Versions) hou116.htm Iwate Prefecture Situation of Road Traffic Regulation Management due to the Earthquake in Iwate Prefecture on March 11 As of 9:3 on August 12 ) 97&of=13 Fukushima River and National Road Office Koriyama National Road Office Disasiter Prevention Imformation Fukushima River and National Road Office Earthquake Imformation 8th Version) Akita Prefecture dex.html Disasiter Prevention Imformation Koriyama National Road Office : Emergency System Response in the 211 off the Pacific Coast of Tohoku Earthquake 2nd, 8th, and 2th Versions) hou1117.htm Miyagi Prefecture Imformation Earthquake 2nd, th, 5th, 6th, and 9th Versions) /index.html Traffic Regulation in the 211 off the Pacific Coast of Tohoku Earthquake As of 16: on May 8) Damag of Pulic Facility and Emergency Disaster Recovery Situations in the 211 off the Pacific Coast of Tohoku Earthquake Updated August 1) x.htm Disasiter Prevention Imformation Banjyo National Road Office : Road Disasiter Prevention Imformation Earthquake 5th Version) Banjyo National Road Office hou1132.htm Yamagata Prefecture Press Release) The 211 off the Pacific Coast of Tohoku Earthquake 3rd and 1th Versions) Main Office Road Division at Disaster Imformation of National Road in the 211 off the Pacific Coast of Tohoku Earthquake 15: on March 18, 211) East Nippon Expressway Company Limited Damaged Routes and Sections List) March 18) Hitachi River and National Road Office Utsunomiya National Road Office Hitachi River and National Road Office Press release) : Announcement for the Damage due to the 211 off the Pacific Coast of Tohoku Earthquake 1:3 on March 12, 211) Road Damage Information for the 211 off the Pacific Coast of Tohoku Earthquake 17: on March 11, 18:3 on March 11, 12: on March 12) Metropolitan Expressway Company Limited Press Release) Influence and Emergency Response due to the 211 off the Pacific Coast of Tohoku Earthquake and Correspondence March 1, 211)

3 N 1 E 11 E 12 E 13 E µ 1 E N 1 E 11 E 12 E 13 E µ 1 E N 36 N 37 N 38 N 39 N 1 E 11 E Fig. 1 Locations of damaged road structures and the related inundation height 11 'E 11 'E Shiogama City 11 2'E 11 2'E 11 'E Damaged Bridges Damaged Roads Roads in 11 'E 12 'E µ km 1 E 38 2'N 38 'N 12 'E 11 3'E a) Ishinomaki City, Shiogama City ) Kesennuma City and Minamisantiku Town and Natori City Fig. 2 Locations of damaged road structures in Miyagi prefecture ^ Epicenter km Natori City Roads in 12 E 13 E ^ ANALYZED DATA OF DAMAGED ROAD STRUCTURES Damaged Roads 39 N 38 N 37 N 36 N 35 N Ishinomaki City 11 E ^ Epicenter ^ Roads in km 12 E 13 E Kesennuma City Minamisanriku Town 39 N 38 N 37 N 36 N 35 N Inundation Height [m] 11 'E Damaged Bridges Damaged Roads Roads in µ km 11 3'E 11 'E 38 'N Tale 1 shows the information on damaged road structures which is opened at the related we sites y road management authorities and local government sectors. Analyzed road structures are national roads at six prefectures of Tohoku regions, Tokyo metropolitan areas and six prefectures of Kanto regions y,, East Nippon Expressway Company Limited and Metropolitan Expressway Company Limited, and prefectural roads at five prefectures of Tohoku regions without Fukushima prefecture y local government sectors. Total numer of data is 68. For selecting 68 data, we remove the damage data to e possily affected y the ground motions due to the aftershocks after March 11, 211. Based on the data, first, we identify the locations of damaged road structures. Second, we select 1 data as the data of damaged road structures due to the tsunami waves y comparing the locations of damaged road structures with 1713

4 Nuner of Damaged Road Structures R1 R2 R3 R R5 R6 R7 R8 R9 R1 R11 R12 R13 R1 R15 R16 R17 R18 R19 B1 B2 B3 B B5 B6 B7 B8 B9 B1 Failure Modes Road Damage Bridge Damage R1 R2 R3 R R5 R6 R7 R8 R9 R1 R11 R12 R13 R1 R15 R16 R17 R18 R19 Souring Wash-away Road Failure Susidence Collapse Wash-away of Pavement Sla and Collapse of Road Shoulder Wash-away of Road Surface and Collapse of Road Surface Collapse of Slope of Emankment Deposits Deposits and Road Bump Deposits and Collapse of Road Shoulder Deposits and Wash-away of Pavement Sla Deposits, Collapse of Road Shoulder and Wash-away of Pavement Sla Deposits and Failure of Pavement Sla Deposits and Fallen rock Deposits, Sumergence of Road and Failure of Slope of Emankment Deposits and Disruption of Road Sumergence of Road Sumergence of Road and Road Failure Fig. 3 Failure modes of damaged road structures estimated inundation areas y GSI 211) and y considering tsunami failure modes for damaged road structures. We verify all data y checking the locations y GoogleEarth. In addition, we add two damaged ridge data located at prefectural roads, Route in Iwate prefecture to 1 data, y identifying the locations of damaged road structures. Finally, total numer of analyzed data is 12. Fig. 1 shows the locations of damaged road structures. Fig. 2 shows the locations of damaged road structures in Miyagi prefecture. 12 data are clarified into two types, road damage and ridge damage. For 19 damaged roads, 55 data are oserved in Miyagi prefecture, 6 data in Iwate prefecture, data in Fukushima prefecture, 3 data in Aomori prefecture and 1 data in Iaraki prefecture. For 33 damaged ridges, 18 data are oserved in Miyagi prefecture, 13 data in Iwate prefecture, and 2 data in Fukushima prefecture. We model suject roads and ridges in estimated inundation areas y GSI 211): y using the digital data of national roads and major prefectural roads in 6 prefectures of Tohoku regions, Tokyo Metropolitan areas and 6 prefectures of Kanto regions offered y National Land Numerical Information Download Service 211) and y constructing the digital data of other prefectural roads in 5 prefectures of Tohoku regions except Fukushima prefecture y checking GoogleEarth. Total length of suject roads is 518km and total numer of suject ridges is 23. B1 B2 B3 B B5 B6 B7 B8 B9 B1 Bridge Bump Failure of Autment Bridge Failure Falling-down Wash-away of Sidewalk of Bridge Wash-away of Emankment of Autment and Falling-down of Service Road Bridge Wash-away of Emankment of Autment and Falling-down Wash-away of Emankment of Autment Deposits Wash-away of Pavement Sla and Failure of Handrail FAILURE MODES OF DAMAGED ROAD STRUCTURES Fig. 3 shows classified 29 failure modes for 19 damaged roads and 33 damaged ridges. 19 data of road damage are classified into 19 failure modes, which are oserved in dominantly 5 deposits R9), 15 wash-aways R2) and 1 road failures R3). 33 data of ridge damage are classified into 1 failure modes, which are oserved in dominantly 2 falling-downs B), failures of autment B2) and 2 deposits B9). From the analysis on aove failure modes, we focus on ridge damage in the following section. 171

5 Group No. Name of Damaged Bridges Longtitude Tale 2 Suject damaged ridges Latitude Name of Roads Failure Modes No. of the Oservetion Sites for Inundation Height 1 Waza Bridge Kadono-hamatamagawa Line of Iwate Prefectural Route 27 B1 2 2 Hirouchi Bridge Noda-osanai Line of Iwate Prefectural Route 268 B3 3 Yoneda Bridge National Route 5 B6 1 No Name Iwaizumi-hiraga-furai Line of Iwate Prefectural Route B No Name Iwaizumi-hiraga-furai Line of Iwate Prefectural Route B 6 5 Mukouwatashi Bridge Omoe-hanto Line of Iwate Prefectural Route 1 B 6 Namiita Bridge National Route 5 B2 2 7 Hinokami Bridge Kamaishi-Tono Line of Iwate Prefectural Route 35 B9 8 Toyasaka Bridge National Route 5 B2 1 9 Katagishi Bridge National Route 5 B2 5 Kawaharagawa Bridge National Route 5 B 1 Numata Overridge National Route 5 B 19 Kesen Bridge National Route 5 B Koizumi Long-ridge National Route 5 B 11 Sodeogawa Bridge National Route 5 B5 8 Nijyuuichihama Bridge National Route 5 B7 12 Utatsu Bridge National Route 5 B 8 Mizushiri Bridge National Route 5 B 13 Oritate Bridge National Route 398 B 8 Yokotsu Bridge National Route 398 B 1 Shin-aikawa Bridge National Route 398 B 1 Kamaya-oosu-ogatsu Line of No Name B8 15 Miyagi Prefectural Route 238 Shin-kitakami Bridge National Route 398 B 16 Onagawa Bridge National Route 398 B 17 Sadakawa Bridge Ishinomakikougyouko-yamoto Line of Miyagi Prefectural Route 27 B Nonohama Bridge Onagawa-oshika Line of Miyagi Prefectural Route 1 B 6 19 Matsugashima Bridge Okumatsushima-matsushimakouen Line of Miyagi Prefectural Route 27 B 6 2 Niramori Bridge Shiogama-shichigahama-tagajyo Line of Miyagi Prefectural Route 58 B Hashimoto Bridge Shiogama-shichigahama-tagajyo Line of Miyagi Prefectural Route 58 B Miyashita Bridge Yuriagekou Line of Miyagi Prefectural Route 129 B Takaura Bridge Somawatari Line of Fukushima and Miyagi Prefectural Route 38 B2 2 2 Ootagawa Bridge National Route 6 B Samekawa Bridge National Route 6 B1 1715

6 Tale 3 Numer of grids for all groups Region Group No. X-direction Y-direction Grid Size[m] 1 All Groups All Groups All Groups , Others ,15,17, ,19, /3) Others , /9) ,19, Others DAMAGE ASSESSMENT OF BRIDGES Analytical framework We define damage ratio of ridges R N as measure of ridge damage y the tsunamis. R N is the ratio of the numer of damaged ridges N d divided y total numer of ridges N t, d t N RN 1) N For the following analyses in calculating the numer of damaged ridges N d at a 2.m interval of inundation heights, we use the simulated data for the corresponding inundation heights at damaged ridges from numerical simulation as descried in the following susection. And in calculating the numer of non-damaged ridges N t -N d ) at a same class of inundation heights, we use the oserved data for the corresponding inundation heights at non-damaged ridges with reliaility level A and B y the 211 Tohoku Earthquake Tsunami Joint Survey Group 211), which are measured in the closest site from suject non-damaged ridge. When we select the corresponding oserved data, if the distance from a non-damaged ridge site to the oservation site ecomes more than 25m, we consider that we do not have the reasonale corresponding oserved data for an inundation height at a non-damaged ridge and we remove the data for the analyses. Finally, we use 33 simulated data for the inundation heights at damaged ridges and 91 oserved data for inundation heights at non-damaged ridges. Numerical simulation for calculating inundation heights at damaged ridges Tale 2 shows suject damaged ridges with failure modes of B1 to B1 in Fig. 3 and corresponding classification of simulation groups for Group 1 to Group 25. For each simulation group, the tsunami wave propagation is computed y using TSUNAMI-CODE Tohoku University s Numerical Analysis Model for Investigation of Tsunami), and the corresponding inundation heights at suject damaged ridges are computed. The governing equations are ased on shallow water theory, which are discretized y using the finite difference method with a staggered leap-flog scheme DCRC 29). We set the value of Manning roughness coefficient n as.25 for all groups. For each simulation group, 1716

7 ,6km,5km,km,3km,2km,1km,km 3,9km 3,8km 3,7km Region 1 5km km 3km Region 2 Region 3 8km 7km 6km 9km -5m -2m -35m -5m -65m -8m -95m,35km,3km,295km,29km,285km,28km,275km Region 535km 5km Region 5 Region 6 55km 55km 555km m 2m m 6m 8m 1m 12m km 5km 2km km 5km 2km a) Region1 to Region3 ) Region to Region6 Fig. Computational oundary for Group 11 simulation 1m 9m 8m 3m Fig. 5 Elevation for Group 11 simulation Red denotes the positions of suject ridges, lue denotes the positions of oservation sites for inundation heights.) 7m 6m 5m m 3m 2m 1m.1m m -1m -2m -3m -m -5m Fig. 6 Inundation areas for Group 11 simulation Red and lue dots donate same meanings as those in Fig. 5) 25m 2m 15m 1m 5m.1m m six computational regions Region 1 to Region 6) are used in the nested grid system. Tale 3 shows the numer of grids in x-direction and y-direction for each simulation group in WGS-198-UTM-5-N coordinate system. Region 1 is used together in all groups. Region 2, Region 3, and Region are used together in Group 1 and Group 12. Region 2, Region 3, and Region are also used together in Group 13 and Group 15. Other Regions are used separately for each simulation group. Region 1 is generated y using GEBCO 3 second data with the grid size of 1,35m. Region 2, Region 3, and Region are generated y using GEBCO 3 second data for topography and JHA 1m-increment-line data for with 1717

8 Simulated Inundation Height [m] Group1 Group2 Group3 Group Group5 Group6 Group7 Group8 Group9 Group1 Group11 Group12 Group13 Group1 Group15 Group16 Group17 Group18 Group19 Group2 Group21 Group22 Group23 Group2 Group25 No. of Exposed Bridges Oserved Inundation Height [m] Fig. 7 Comparison of oserved inundation heights with simulated results Inundation Height[m] No. of Damaged Bridges a) Numer of exposed ridges ) Numer of damaged ridges Fig. 8 Frequency of suject ridges y an inundation height B9 B B1 B 6 B9 B B1 B2 B B2 B8 B B B2 B6 B5 B B B B3 B Inundation Height[m] the grid size of 5m, 15m, and 5m, respectively. Region 5 and Region 6 are generated y using GSI DEM 1m-point data for topography and JHA 1m-increment-line data for athymetry with the grid size of /3) m and /9) m. Fig. a) shows the computational oundary of Region 1, Region 2, and Region 3 for Group 11 simulation. Fig. ) shows the computational oundary of Region, Region 5, and Region 6 for Group 11 simulation. The time step for computation is.15 second, and total computational time is 12 minutes for all groups. The tsunami source model proposed y Imamura et al. 211) is used for the simulation. We give the initial water level ased on the tsunami source model y using Okada s method Okada 1985). By the limitation of paper lengths, we show the results for the typical simulation to validate the simulated inundation data with oserved data. Fig. 5 shows the elevation from the topography and athymetry data used for Group 11 simulation. It also shows the positions of suject three ridges and the related twenty four oservation sites for inundation heights with reliaility A and B, y the 211 Tohoku Earthquake Tsunami Joint Survey Group 211). Fig. 6 shows the inundation areas for Group 11 simulation. From the results y Group 11 simulation for Koizumi Long-ridge areas, simulated inundation heights show the values of 8.92m to 2.83m, which have the differences y -1.6m to 1.9m compared with oserved values. It indicates that simulated inundation heights ecome.9 to 2.28 times compared with the oservation data. Fig. 7 shows the relationship etween the simulated inundation data from Group 1 to Group

9 Damage Ratio Inundation Height [m] Fig. 9 Relation etween damage ratio R N and inundation heights for wash-away ridges E 11 E 12 E 13 E µ 1 E N 39 N Fig. 1 Spatial distriutions of damage ratio R N simulations and related oservation data. Group 6 simulation data show 1. times to 1.3 times inundation heights compared with the related oserved data and give relatively higher accuracy than other simulation data. In contrast, Group 3 simulation data show.93 times to 2.85 times inundation heights compared with the related oserved data and show relatively lower accuracy than other simulation data. The magnification factors of total simulated inundation data with oserved data vary from.51 to Based on this validation, we use the simulated inundation heights data at suject damaged ridges as input inundation heights acting on their ridges in consideration of accuracy for simulated results as shown in Fig. 7. Damage ratio of wash-away ridges ^ Epicenter ^ Roads in km Fig. 8a) shows the frequency of the numer of exposed ridges N t y an inundation height, including non-damaged ridges and damaged ridges. These data are classified in a 2m-interval inundation height. N t with inundation heights of.m to 6.m shows the largest value of 22. Fig. 8) shows the frequency of the numer of damaged ridges N d y an inundation height, in which includes all failure 38 N 37 N 36 N 35 N 1719

10 modes of ridge damage of B1 to B1 denoted in Fig. 3. These data are also classified in a same interval. N d with inundation heights of 1.m to 16.m shows the largest value of 7. We calculate ridge damage ratio R N at a 2.m interval of inundation heights ased on Eq. 1) y selecting falling-down failure mode B). Fig. 9 shows the relation etween the damage ratio R N and inundation heights. Fig. 1 shows the spatial distriutions of damage ratio R N. From Fig. 9, R N with inundation heights of.m to.m show zero, R N with inundation heights of.m to 6.m increases slightly to., R N with inundation heights of 6.m to 16.m increases to the values of.18 to.33, R N with inundation heights of 16.m to 18.m increases to the large value of.5, and R N with inundation heights of 18.m to 2.m shows the largest value of.75. From Fig. 1, highest R N is oserved at Motoyoshi Town, Kesennuma City, Miyagi Prefecture for Koizumi Long-ridge areas Group 11) and Tanohata Village, Iwate Prefecture for No-name ridge Group ). CONCLUSIONS We assessed the tsunami damage on road structures due to the 211 off the Pacific Coast of Tohoku earthquake tsunami. We collected 12 damage data of road structures due to the tsunamis opened at the related we sites for analyses and classified 29 failure modes. For damage assessment of ridges, we otained the inundation heights at damaged ridges due to the tsunamis y series of tsunami flow simulation ased on shallow water theory, which are discretized y using the finite difference method with a staggered leap-flog scheme DCRC 29). Finally, we calculated damage ratio R N dependent on an inundation height, which is defined y the value of numer of ridge damage points N d divided y total numer of exposed ridges N t, focusing on wash-away ridges. 1) For 19 damaged roads, failure modes are classified into 19 types, which are oserved in dominantly 5 deposits, 15 wash-aways and 1 road failures. For 33 damaged ridges, failure modes are classified into 1 types, which are oserved in dominantly 2 falling-downs, failures of autment and 2 deposits. 2) Simulated inundation heights at 33 damaged ridges are verified y comparing these related data with oserved data y the 211 Tohoku Earthquake Tsunami Survey Group 211). The magnification factors of total simulated inundation data with oserved data varied from.51 to ) R N with inundation heights of.m to.m show zero, R N with inundation heights of 2.m to.m increases slightly to., R N with inundation heights of 6.m to 16.m increase to the value of.18 to.33, R N with inundation heights of 16.m to 18.m increases to the large value of.5 and R N with inundation heights of 18.m to 2.m shows the largest value of.75. Highest R N is oserved at Motoyoshi Town, Kesennuma City, Miyagi Prefecture for Koizumi Long-ridge areas and Tanohata Village, Iwate prefecture for No-name ridge areas. ACKNOWLEDGEMENTS The authors acknowledge valuale supports for numerical simulation for calculating inundation heights at suject ridges from Disaster Control Research Center, Tohoku University Professor F. Imamura and Professor S. Koshimura). The authors also appreciate valuale cooperation for calculating inundation heights at damaged ridges from Mr. Y. Hiraki and Mr. Y. Ezura at University of Tsukua. REFERENCES Disaster Control Research Center, Tohoku University. Tohoku University s Numerical Analysis Model for Investigation of Tsunami. TUNAMI-CODE. 172

11 Geospatial Information Authority of Japan GSI). Digital Elevation Model. n/etsuran.html. Imamura, F., Koshimura, S., Murashima, Y., Akita, Y. and Aratani, Y. 211). The tsunami simulation for The 211 off the Pacific Coast of Tohoku earthquake tsunami, Tohoku University Model version1.1). Disaster Control Research CenterDCRC), 1-6. Japan Hydraulic Association JHA). Digital Topography of Ocean Floor M7 Series. National Land Numerical Information Download Service. Digital Road Data. sj/. Okada, Y. 1995). Surface deformation due to shear and tensile faults in a half-space. Bull. Seismol. Soc. Am., Vol. 75, The 211 Tohoku Earthquake Tsunami Joint Survey Group. Result of tsunami surveys. coastal.jp/tsunami211/index.php. The General Bathymetry Chart of the Oceans GEBCO)