講演資料「Tsunami Impacting Eastern Japan and Preparedness for Extraordinary Natural Disaster 」(抜粋)(PDF/3.8MB)

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(1)May 25, 2011. Tsunami Impacting Eastern Japan and P Preparedness d ffor Extraordinary E t di N Natural t l Di Disaster t. Takehiko Fujita Acting President Port and Airport Research Institute, Japan.

(2) Contents. 1 Outline 1. O li off the h earthquake h k 2 Measured strong motion 2. 3. Measured tsunami height 4. Evaluation of effects of previous countermeasures 5. Preparation against extraordinary tsunami.

(3) Source region of the earthquake. ×. http://alterman47.wordpress.com http://www.sonpo.or.jp. Approximate source region of the earthquake. ‘X’ denotes the epicenter.. The pacific plate is subducting beneath the continental plate at the Japan trench. The earthquake occurred between the two plates..

(4) A large number of aftershocks Distribution of aftershocks with M≧5.0 ≧. C Cumulative number off aftershocks f (Japan Meteorological Agency). More than 400 aftershocks with M≧5.0 have occurred as of May 13 13. (Japan Meteorological Agency). The e ssize eo of tthe e ccircle c e indicates d cates ea earthquake t qua e magnitude. Five aftershocks with M≧7.0 have occurred as of May 13..

(5) Great amount of subsidence due to coseismic slip Horizontal displacement GPS. Vertical displacement GPS. 530 cm at Oshika 120 cm at Oshika (Geospatioal Information Authority of Japan). A great amount of horizontal and vertical displacement occurred due to coseismic slip. The Oshika Peninsula subsided about 120cm according to GPS observation by the Geospatial Information Authority of Japan Japan. The sea floor around the epicenter moved 24m according to Japan Coast Guard. The movement was as large as 50m according to JAMSTEC..

(6) A large number of strong motion data was successfully recorded by the “Strong Motion Earthquake Observation in Japanese Ports”.

(7) Design ground motions for Japanese Ports Two kinds of design ground motions are considered in the seismic design of Japanese port structures. The Level-1 design ground motion is defined as a ground motion with the annual probability of exceedance of 1/75. The Level-2 design ground motion is so called “the worst case scenario” ground motion..

(8) Comparison with design ground motions - The case of Onahama Port frequencies relevant to major damage to port structures. It is quite natural that the observed ground motion exceeded the Level-1 design ground motion. The observed ground motion was close to the Level-2 design ground motion at frequencies relevant to major damage to port structures (0.31Hz). But at higher frequencies, the observed ground motion exceeded the Level-2 design ground motion. In the case of Onahama, the Level-2 design ground d motion ti was b based d on a scenario i earthquake th k with ith magnitude it d 6 6.5 5 (b (butt jjustt beneath the port). The appropriateness of the scenario should be investigated once more..

(9) GPS-mounted wave buoy 40m 4.0 1m 6.3 m. Aomori East Iwate North Iwate Central. 6.7 m. Iwate South. ①. ②. ③. ④. ⑤. ⑥. ⑦. Miyagi y g North. 5.6 m Miyagi Central. highest crest 2.6 m. Fukushima. 14. 15. 16. 17 18 19 Time (hour). 20. 21. 22.

(10) Tsunami height measured and estimated Run-up height. Inundation height g Estimated inundation height at the shoreline. 0. 5. 10. 15 20 25 Tsunami height (m).

(11) Damages of breakwater. Landward. Landward. Landward.

(12) Kamaishi Tsunami Breakwater +6m. Meiji Sanriku Earthquake (1896). +6 m. 5m +4 m △. 2.8 m Less than 0.5 m. Tsunami breakwater. Tsunami seawall.

(13) Simulation results for the ToHoku Earthquake in 2011 The 2011 off the Pacific Coast of Tohoku Earthquake (2011). Without Breakwater. With Breakwater. This tsunami simulation is conducted by ‘Storm Surge and Tsunami Simulator in Oceans and Coastal Areas ((STOC)’, ) which is developed p by PARI..

(14) Effect of breakwater. With Breakwater. Wa ater surface e elevation n (m). Without Breakwater Arrival time 6 minutes delay (tsunami height of 4 m) with breakwater without. Tsunami height (m). Tsunami height 13.7 m → 8.0 m. Time after earthquake (min).

(15) Effect of breakwater Without breakwater. Tsunami height 13.7 m. Run-up height 20.2 m. 4-m-height seawall 28 min for overtopping pp g With breakwater Tsunamii height T h i ht 10.8 m. Tsunami height g 8.0 m. Tsunami Breakwater. Run-up height 10 0 m 10.0. 4-m-height seawall 36 min for overtopping.

(16) Tsunami damages. Quay damaged by the combination of earthquake and tsunami (Soma) Scattered containers (Sendai). Tilted floating dock (Kuji). Collapsed crane (Kashima).

(17) Tsunami damages. Drifted tank trucks (Sendai). Destroyed seawall (Taro). Ship drifted in a town (Kesennuma). Smashed oil tank and oil spill (Kesennuma).

(18) Tsunami damages Washed vehicles and debris (Kamishi). Burned wooden houses and vehicles (Ishinomaki). Broken and tilted buildings (Onagawa). Piles es were e e pu pulled ed out out. Collapsed building (Onagawa).

(19) Liquefaction remediation Sendai Airport March 13. March 18. Th liquefaction The li f ti counter t measure off runway h had d ended, d d however, the taxiway was being prepared. Infiltration Solidification X-Jet Grouting. River culvert.

(20) Liquefaction remediation Sendai Airport March 20. March 18. Improved runway. The runwayy keeps p ‘Serviceability’ y jjust after the Earthquake. However, It took one week to cleanup the debris due to Tsunami.. Apron and Boarding bridge March 20. The operation of the passenger plane restarted on April 13. There are serious subsidence, subsidence uneven settlements and clacks on the surface of un-improved taxiway. It lost the ‘Serviceability’ and the ‘Reparability.’. Un-improved taxiway.

(21) Sendai Port: Base Isolated Gantry Crane 4 Gantry y Cranes : 2 base-isolated cranes 2 non-base-isolated cranes. Damage occurred in one non-base-isolated crane Direction of Land and Sea 横行方向. ダンパ Oil Dumper. ISOLATOR アイソレ－タアイソレタ. 平行 Parallel Motion Link リンク. Trigger Pin シアピンモ－メント受けロ－ラ. Moment Transmission Bearing. Base Isolation system. Patent holder : PARI and Mitsui Engineering & Shipbuilding Co, Ltd.. Base-isolated cranes: No structural damage.

(22) Future Improvement in Information Network Present System Mutsu-Ogawara Port Hachinohe Port. Shiogama Port Sendai New Port. strong motion observation site GPS buoy. Miyako Port. coastal wave gauge. land station. tide gauge house. land station. Kamaishi Port. Tohoku B* and Port Offices * Ports and Airports Division, Tohoku Regional Development Bureau. Central Miyagi. Idea for Future System Toward redundant system !! Packet data transmission - Mobile M bil phone h (NTT FOMA, FOMA etc.) t ) - Satellite phone (INMARSAT, Iridium, etc.). Onahama Port. National b k center? backup ?. Hitachi-naka, Ibaraki Port Kashima Port. PARI. ★. PARI. land station. North Miyagi. Soma Port. Kanto District. NTT telephone p line,, on demand. Kuji Port. Tohoku District Ofunato Port. earthquake, tsunami, communication disturbance. strong motion sensor GPS Buoy coastal wave gauge tide gauge damaged or lost sensor. strong motion observation site. NTT telephone line, automatically. GPS buoy. land station. coastal wave gauge. land station. tide gauge house. repeater station. PARI Tohoku B B* and Port Offices.

(23) Recommended countermeasures against tsunami Level 1. Level 2. Design tsunami Design tsunami Largest tsunami in modern times modern times (return period: around 100 years) One of the largest tsunamis in history (return period: around 1000 years). Required performance Required performance • To protect human lives • To protect properties To protect properties • To protect economic activities. • To protect human lives • To reduce economic loss, especially by preventing the occurrence of severe secondary disasters and by enabling prompt disasters and by enabling prompt recovery Disaster prevention facilities such as seawalls should be safe against ‘Level 2 tsunami’. At least, in the event of ‘Level 2 tsunami’, the deformation of these facilities have to be not so large to maintain the performance to reduce tsunami..

(24) Issues on Preparedness Against Extraordinary Tsunami Hazard Map ・ To prepare hazard maps and scenarios against tsunamis of levels 1 & 2. Evacuation E ti ・ To develop and implement the real-time tsunami prediction based on the y GPS-mounted wave buoys. y data observed by ・ To establish secure and reliable warning systems and evacuation routes in consideration of blackout and traffic. ・ To T prepare shelters h lt that th t are secure even against i t level l l 2 ttsunami. i Urban Plan ・ To make higher grounds such as artificial grounds, embankment, and reclamation lands. ・ To make houses rigid. rigid Recommended material is not wood but concrete concrete. ・ To make local people to construct their houses at hill areas. ・ To p provide access from hill areas to commercial areas in coastal zone. ・ To build tall buildings that have residential areas in upper floors and commercial areas in lower floors..

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