Chapter 4 Seismic Risk Assessment
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The Project for Assessment of Earthquake Disaster Risk for the Kathmandu Valley in Nepal Final Report (Main Report) Chapter 4 Seismic Risk Assessment Seismic risk assessment was carried out as the update of the risk assessment of 2002 JICA project of “The Study on Earthquake Disaster Mitigation in the Kathmandu Valley” for the purpose of providing basic information for the formulation of disaster risk reduction and management plans for pilot municipalities. The assessment was performed based on the latest available data and taking into account the new research results on risk assessment as well as the characteristics of ground motion, building damage and human casualties caused by the Gorkha Earthquake, which occurred on 25 April 2015, right before the commencement of the project. The main features of risk assessment of this project are summarized as below. No building inventory, which is important for risk assessment, exists in KV. In order to establish building inventory, building survey for all buildings was made by the project for former Lalitpur Sub-metropolitan City and Bhaktapur municipality. In addition, building information for all buildings in Budhanilkantha and former Karyabinayak municipalities was collected. The building inventory for the other municipalities were created by estimation based on satellite image and sample structure type survey. The damage function of buildings was developed based on the building damage data of the Gorkha Earthquake as well as the seismic resistant capacity analysis of typical structures of Nepal. Nonlinear flexural deformation of RC piers subject to seismic excitation was estimated by a statistical method and was used to classify the damage degree of bridges. Human casualties were estimated based on the death rate and injured rate of the Gorkha Earthquake for different damage levels and different structure types. Three earthquake occurrence scenes: night, weekday noon and weekend afternoon, were considered for human casualty estimation. Building damage and human casualties were also estimated for 2030 for the purpose of determination of disaster risk reduction target, assuming different cases of structure type distribution. The contents of seismic risk assessment cover structural damage of buildings, roads, bridges, 4-1 The Project for Assessment of Earthquake Disaster Risk for the Kathmandu Valley in Nepal Final Report (Main Report) water supply pipelines, sewage pipelines, power poles and mobile base transceiver station (BTS) towers as well as human casualties and the direct economic loss and impact on the tourism industry. The summary of risk assessment results is shown in Table 4.1 Seismic risk assessment results from one scenario ground motion are shown in the main report as an example. A map book, which includes all of the risk assessment results together with the basic information for seismic hazard and risk assessment as well as seismic hazard results, was compiled for easy reference. The contents of the map book are given in Table 4.2. REMARKS The scenario earthquakes are not the prediction of future earthquakes. Risk assessment was carried out based on scientific research and investigation results but with inevitable assumptions. Its results might have uncertainties and are not the guarantee of the future damage of a scenario earthquake. The purpose of risk assessment is to provide basic information for the development of disaster risk reduction and management plan of pilot municipalities in KV. 4-2 The Project for Assessment of Earthquake Disaster Risk for the Kathmandu Valley in Nepal Final Report (Main Report) Table 4.1 Summary of risk assessment results Physical Damage Economic Loss (mil. NPR)*1 Human Casualty (Population: 2016: 2,786,929; 2030: 3,805,926) Category Scenario Earthquake Ground Motion Scenario Earthquake Ground Motion Scenario Earthquake Ground Motion WN CNS-1 CNS-2 CNS-3 WN CNS-1 CNS-2 CNS-3 WN CNS-1 CNS-2 CNS-3 Night (Weekday and weekend) 3,034 9,133 22,179 35,726 24,961 65,314 136,060 199,643 Death 0.11% 0.33% 0.80% 1.28% Heavy damage 11,880 35,766 86,861 139,914 (EMS DL4&5) Injured 0.43% 1.28% 3.12% 5.02% 5.6% 14.7% 30.6% 44.9% 279,031 642,743 1,196,080 1,613,314 Evacuee 10.01% 23.06% 42.92% 57.89% Weekday (noon, 12:00) 2,784 8,282 19,959 31,956 21,967 42,940 62,691 67,418 Death 0.10% 0.30% 0.72% 1.15% Building (2016) Moderate damage 132,999 371,003 761,531 1,098,353 10,905 32,435 78,168 125,152 (Total building 444,554) (EMS DL3) Injured 0.39% 1.16% 2.80% 4.49% 4.9% 9.7% 14.1% 15.2% 285,850 652,798 1,206,530 1,619,792 Evacuee 10.26% 23.42% 43.29% 58.12% Weekend (afternoon, 18:00) 2,123 6,393 15,526 25,008 43,564 67,770 77,713 70,462 Death 0.08% 0.23% 0.56% 0.90% Slight damage 8,316 25,036 60,803 97,940 (EMS DL2) Injured 0.30% 0.90% 2.18% 3.51% 9.8% 15.2% 17.5% 15.9% 279,942 645,483 1,202,734 1,624,032 Evacuee 10.04% 23.16% 43.16% 58.27% 33,763 88,681 185,796 273,269 4,121 12,508 30,583 49,381 Case-0 Death 5.6% 14.6% 30.6% 45.1% 0.11% 0.33% 0.80% 1.30% 28,377 79,075 171,977 258,044 3,434 11,017 27,930 46,017 Case-1 Death 4.7% 13.0% 28.4% 42.5% 16.7% 11.9% 8.7% 6.8% 13,627 56,452 146,361 234,477 1,721 8,135 24,356 42,526 Case-2 Death Building (2030) 2.2% 9.3% 24.1% 38.7% 58.2% 35.0% 20.4% 13.9% (Heavy damage, Total building 606,506)*2 12,162 49,970 131,095 213,481 1,438 6,733 20,526 36,715 Case-3 Death 2.0% 8.2% 21.6% 35.2% 65.1% 46.2% 32.9% 25.6% 16,147 52,413 129,904 210,181 2,052 7,887 23,086 41,146 Case-4 Death 2.7% 8.6% 21.4% 34.7% 50.2% 36.9% 24.5% 16.7% 11,138 41,230 111,854 189,357 1,476 6,524 20,842 38,733 Case-5 Death 1.8% 6.8% 18.4% 31.2% 64.2% 47.8% 31.9% 21.6% 237 737 1,654 2,486 Heavy damage 444 1,545 4,002 6,555 4.1% 12.9% 28.9% 43.4% Death School 253 539 810 875 0.05% 0.18% 0.47% 0.77% Moderate damage 20,462 51,231 98,171 134,932 (Total building 5,731) 4.4% 9.4% 14.1% 15.3% 1,739 6,051 15,673 25,671 568 916 1,057 960 Injured Slight damage 9.9% 16.0% 18.4% 16.8% 0.20% 0.71% 1.84% 3.02% 20 64 153 235 Heavy damage 3.4% 11.0% 26.2% 40.2% Health facility 24 55 83 94 Moderate damage 27,534 68,588 165,683 232,782 (Total building 584) 4.1% 9.4% 14.2% 16.1% 51 85 105 97 Slight damage 8.7% 14.6% 18.0% 16.6% 20 59 126 186 Heavy damage 4.2% 12.3% 26.4% 38.9% Government building 20 44 66 73 Moderate damage 2,444 8,669 16,514 22,708 (Total building 478) 4.2% 9.2% 13.8% 15.3% 44 71 85 80 Slight damage 9.2% 14.9% 17.8% 16.7% Length in landslide 0 6.6 98.5 390.6 area (km) Road*3 0.0% 0.1% 1.7% 6.7% 0 471 1,620 2,878 (Total length 5,811 km) Length in liquefaction 0 76.1 274.9 455.3 area (km) 0.0% 1.3% 4.7% 7.8% 0 1 12 32 Heavy damage 0.0% 2.2% 26.7% 71.1% Bridge 2212711 Moderate damage 377 898 1,359 1,914 (45 bridges assessed)*4 4.4% 46.7% 60.0% 24.4% 18 17 6 2 Slight damage 40.0% 37.8% 13.3% 4.4% 982 1,921 3,496 5,161 Water supply (Existing) Damage points 36 71 129 191 (Total length 1,167 km) 0.84 1.65 3.00 4.42 124 255 460 676 Water supply (Planned) Damage points 5 9 17 25 (Total length 699 km) 0.18 0.36 0.66 0.97 Sewage 4.81 8.15 11.94 18.21 Damage Length (km) 76 135 200 290 (Total length 1,192 km) 0.4% 0.7% 1.0% 1.5% 1,327 3,991 9,156 13,992 Power distribution Pole broken 19 56 129 197 (Total pole 190,851) 0.7% 2.1% 4.8% 7.3% Mobile BTS tower 43 143 372 601 Tower damage 82 272 707 1,142 (Total tower 1,043) 4.1% 13.7% 35.7% 57.6% Source: JICA Project Team 4-3 The Project for Assessment of Earthquake Disaster Risk for the Kathmandu Valley in Nepal Final Report (Main Report) Table 4.2 Contents of Map Book No. Caption No. Caption A. Basic Conditions C. Earthquake Risk Assessment A-1 Study Area and Pilot Municipality C-1 Distribution of Heavily Damaged Building & Ratio in 2016 (WN) A-2 Distribution of Population in 2016 at Night C-2 Distribution of Heavily Damaged Building & Ratio in 2016 (CNS-1) A-3 Distribution of Estimated Population in 2030 at C-3 Distribution of Heavily Damaged Building & Ratio in 2016 Night (CNS-2) A-4 Building Distribution in 2016 C-4 Distribution of Heavily Damaged Building & Ratio in 2016 (CNS-3) A-5 Estimated Building Distribution in 2030 (without C-5 Distribution of Moderately Damaged Building & Ratio in 2016 BSPS) (WN) A-6 Estimated Building Distribution in 2030 (with BSPS C-6 Distribution of Moderately Damaged Building & Ratio in 2016 Case-1) (CNS-1) A-7 Estimated Building Distribution in 2030 (with BSPS C-7 Distribution of Moderately Damaged Building & Ratio in 2016 Case-2) (CNS-2) A-8 Estimated Building Distribution in 2030 (with BSPS C-8 Distribution of Moderately Damaged Building & Ratio in 2016 Case-3) (CNS-3) A-9 Estimated Building Distribution in 2030 (with BSPS C-9 Distribution of Heavily Damaged Building for 2030 without Case-4) BSPS A-10 Estimated Building Distribution in 2030 (with BSPS C-10 Distribution of Heavily Damaged Building for 2030 with BSPS Case-5) Case-1 A-11 Distribution of School Building C-11 Distribution of Heavily Damaged Building for 2030 with BSPS Case-2 A-12 Distribution of Health Facility Building C-12 Distribution of Heavily Damaged Building for 2030 with BSPS Case-3 A-13 Distribution of Government Building C-13 Distribution of Heavily Damaged Building for 2030 with BSPS Case-4 A-14 Road Network C-14 Distribution of Heavily Damaged Building for 2030 with BSPS Case-5 A-15 Emergency Transportation Road Network (ETRN) C-15 School Building Damage Proposed by JICA RRNE A-16 Distribution of Bridge C-16 Health Facility Building Damage A-17 Distribution of Water Supply Network (Existing) C-17 Government Building Damage A-18 Distribution of Water Supply Network (Planned) C-18 Possible Damage of Road by Liquefaction A-19 Distribution of Sewage Network C-19 Possible Damage of Road by Slope Failure A-20 Estimated Power Pole Distribution C-20 Possible Link Blockage of Road by Building Damage A-21 Distribution of Mobile BTS Tower C-21 Possible Link Blockage of ETRN by Building Damage C-22 Damage of Bridge B.