Proceedings of the International Symposium on Engineering Lessons Learned from the 2011 Great East Japan Earthquake, March 1-4, 2012, Tokyo, Japan TSUNAMI INVERSION ANALYSIS OF THE GREAT EAST JAPAN EARTHQUAKE Makoto TAKAO 1, Tomoyuki TANI 1, Toshimichi KANETO 1, Ken YANAGISAWA 1, Tadashi ANNAKA 2 1 Tokyo Electric Power Company, Tokyo, Japan 2 Tokyo Electric Power Services Company, Tokyo, Japan, ABSTRACT: We carried out a tsunami inversion analysis and built a tsunami source model for the Great East Japan Earthquake. We focused attention on the a) tide record, b) flooding height and run-up height, c) crustal movement and d) inundated area. The proposed source model with a magnitude (Mw) of 9.1 consists of mutually independent 80 blocks. The maximum fault slip amount which is located near the trench axis is 56.7m. We confirmed that the observed tsunami data, especially the four parameters described above, were reproduced quite accurately via the model in a well balanced manner. Key Words: The Great East Japan earthquake, tsunami inversion analysis, tide record, tsunami height, crustal movement, inundated area, tsunami source model INTRODUCTION The tsunami caused by the Great East Japan Earthquake on March 11, 2011, struck the Pacific coast of Hokkaido, Tohoku and Kanto regions. This great earthquake and giant tsunami invited heavy losses in the northeastern region of Honshu Island. This event occurred on the boundary between the Pacific and the Eurasian plates. It was thought that the rupture area extended widely from the region off the coast from Iwate to Ibaraki prefectures. The focal mechanism was estimated as a reverse fault with a compression axis in a WNW-ESE direction. The Headquarters for Earthquake Research Promotion (2002) and Japan Society of Civil Engineers (2002) had evaluated the earthquake and tsunami for mutually individual regions such as the offing of the Miyagi prefecture, the offing of the south Sanriku along the trench and the offing of Fukushima prefecture. According to the evaluation, an occurrence of the simultaneous movement of all these regions was beyond the assumption. This huge tsunami was recorded at numerous points in many parameters, such as the tide record, flooding height, run-up height, crustal movement, inundated area etc. For the purpose of investigating the mechanism of the earthquake and tsunami, we conducted an analysis on the basis of those records. As for tsunami source model, some inversion models have been proposed for the purpose of reproducing the tide record, such as Fujii et al. (2011), Tanioka (2011). However, there was no model that could be used to reproduce the tide record, flooding height, run-up height, crustal movement and inundated area in a well-balanced manner. We carried out a tsunami inversion analysis with the aim of building a well-balanced tsunami source model and reproducing an observed tsunami via numerical 622
simulations. SURVEY RESULTS The target parameters of our inversion were the a) tide record, b) flooding height and run-up height, c) crustal movement and d) inundated area over a broad area (Hokkaido Chiba Pref.). At first we collected recorded data concerning those four parameters. We used the data measured by the Japan Meteorological Agency (2011), Ports and Harbors Bureau, Ministry of Land Infrastructure, Transport and Tourism (2011), National Oceanic and Atmospheric Administration (2011) and Earthquake Research Institute, University of Tokyo (2011) etc. as to the observed tide record. The digital data with time intervals of 10 seconds was created for each point using the published tide record. The analog data was digitalized from paper. As for the observed flooding height and run-up height, we used the results by The 2011 Tohoku Earthquake Tsunami Joint Survey Group (2011) from Hokkaido to Chiba Pref. and by our trace survey in Fukushima Pref. The prerelease version by the Joint Survey Group was used for this study. Among all 3,256 data points by the Joint Survey Group, the following data was excluded and we used a total of 2,820 points. Data without location information or flooding height and run-up height Data whose degree of confidence is D or W (small tsunami) Data with the same latitude, longitude and wave height as those of other data Data whose degree of confidence of the elevation is low (data with the description of using Google map ) Data with description due to local geography or splashes Data with descriptions such as a larger tsunami hit etc. Data whose trace mark is widely displaced from the coastline to the seaside or landside Data with negative values and data of 10cm or less Data having the discrepancy with the content in the comments column regarding the flooding height and run-up height Data whose distance from the coastline exceeds 1km and the height is less than 1m As for the crustal movement, we used the results measured by the Geospatial Information Authority of Japan (2011a) for land areas and the Japan Coast Guard (2011) for marine areas. As for the inundated area, the aerial photos and satellite images taken after the earthquake were used to decipher inundated areas. We divided the area into 73 regions. And we used the results by The Geospatial Information Authority of Japan (2011b) from Aomori to Chiba Pref. and by us in Fukushima Pref. TSUNAMI INVERSION In order to study the tsunami caused by the Great East Japan Earthquake, we carried out a tsunami inversion analysis with the aim of building a well-balanced tsunami source model using observed records. We focused attention on the tide record, flooding height, run-up height, crustal movement and inundated area. Method of Tsunami Inversion Analysis We used the tsunami inversion method proposed by Annaka et al. (1999). In our inversion, we extended Annaka et al. (1999) for including the data of crustal deformation and the inundated area. Essentially the nonlinear inversion is needed for the inversion based on a nonlinear tsunami analysis. However, it is difficult to put the nonlinear inversion into practice because of the vast computational 623
time. Instead of the nonlinear inversion, the linear inversion using the Green function based on the linear tsunami analysis was used by converting the data in the nonlinear space (real space) to the data in the linear space. The conversion was conducted based on the relationship of the calculated values between the nonlinear tsunami analysis and the linear tsunami analysis. In the linear inversion, the following function J, the error sums of squares, is minimized. C L n 2 1 n o c J C1 10 ( A Conv.) i log10 ( AL ) i 2 2 ki o c C Z ( t ) Z ( t ) log i 1 n3 3 o c ( B ) i, j ( B i, j 2 i 1 j 1 2 n C3 ) 2 4 o c 4 log10 ( I Conv.) i log10 ( I L ) i i 1 j 1 i 1 NL j C (1) O where n i : number of data, C i : weighting factor, A Conv. : converted tsunami height from observed value, A : maximum value of calculated tsunami wave, Z O ) : amplitude of tide record at time t j, Z C L ( t j NL ( t j ) : amplitude of calculated tsunami wave at time t j, B O : observed value of crustal deformation in j-th direction, B C : calculated value of crustal deformation in j-th direction, from observed inundation area, I L C I O Conv. : converted value : calculated value for representing inundation area. Calculated tsunami waves are obtained by the summation of Green functions from the fault slip distribution. The weighting factors are normally determined so that the error sums of squares for the four kinds of data become nearly equal. The nonlinear tsunami analyses were conducted using the fault slip distribution obtained by the linear inversion and the fitness between the observed and calculated data was evaluated. When the fitness was insufficient, the converted values used in the linear inversion were revised based on the added nonlinear tsunami analyses. Iterations of linear inversion and nonlinear tsunami analysis were continued until the converted values become unchanged and the fitness was sufficient. The conditions for the linear tsunami analysis are as follows. Basis equation : Linear long wave equation Computational scheme : Staggered grid in leap-frog method Initial displacement : Method by Mansinha and Smylie (1971) Calculated grid division : Shown in Fig.1. The basic grid interval was set to 1350m, and the grid interval was decreased to 450m, 150m, and 50m as land approaches. For a nonlinear tsunami analysis, the nonlinear long wave equation was used and a run-up calculation was conducted taking the land topography into account. Tsunami Source Model The tsunami source model consists of the aggregate of small fault blocks. This is because the shape of the plate boundary surface could be described correctly. A slip angle of a small fault block was defined for each small fault block based on the direction of the relative plate motion, i.e. N65 W. We defined the 1,255 small fault elements and arranged them into 80 blocks. The slip amount was set constant in each block in this paper. And we determined the slip amount at each block using the tsunami inversion analysis. Here, we assumed that the rupture start time and duration time is constant for all blocks in this inversion model. As a result of the inversion analysis we got the fault slip distribution shown in Fig.2 as the tsunami source model. The moment magnitude (Mw) of this model is 9.1. The fault slip amount is particularly large near the trench axis (maximum slip amount of 56.7m), which shows the same tendency as the model by Fujii et al. (2011) based on the tide record. We presumed that this is because a large inter-plate earthquake near the Japan trench (tsunami earthquake type) occurred at the same time as the inter-plate earthquake off the coast of Miyagi Prefecture and Fukushima Prefecture, and that resulted in the occurrence of large slips along the ocean trench. i L j i 624
135km Fig.1 Calculation grid division (1350m in aqua, 450m in green, 150m in yellow, and 50m in red) [m] Fig.2 The fault slip distribution; 80 blocks 625
NUMERICAL SIMULATION USING THE OBTAINED TSUNAMI SOURCE MODEL Finally, we carried out numerical simulations, a nonlinear forward analysis, using the proposed tsunami source model shown in Fig.2. A comparison of the observed and the analyzed tsunami is as follows. A comparison of the flooding height and run-up height is shown in Fig.3. In comparison with the 2,820 data points, this model reproduces the tsunami height in K=1.04 and κ=1.40 ; reproduction index by Aida (1978). These values satisfy the criteria established by the Japan Society of Civil Engineers (2002), that is 0.95<K<1.05 and κ<1.45. There are some regions where there is a difference, but in general, the flooding height and run-up height are reproduced quite accurately via our inversion model. A comparison with the tide record is shown in Fig.4. The overall reproducibility is good, and in particular, the reproducibility of the waveforms of Kushiro and Iwate(M) are good. The comparisons of the crustal movement observed in the land areas are shown in Fig.5 and that in the marine areas are shown in Fig.6. The reproducibility of the GPS measurement in the land areas is good. In the horizontal direction in the marine areas, the reproducibility is good in general, and the direction is reproduced quite well. In the vertical direction, offshore Miyagi 1, which has the maximum displacement, is reproduced well, however there is one point where direction is reversed. A comparison of the inundated area is shown in Fig.7. The inundated area from Aomori Prefecture to Chiba Prefecture is reproduced well. 45 40 Observed Calculated 40 35 Tsunami Hight(m) 30 20 10 30 25 20 15 10 5 0 96 68 43 15 14 18 21 24 27 30 33 36 39 42 46 49 52 55 58 61 64 67 71 74 77 80 83 86 89 92 95 99 11 13 17 20 26 29 32 35 38 41 45 48 51 54 57 60 63 66 70 73 76 79 82 85 88 91 94 98 12345678910 16 19 22 25 28 31 34 37 40 44 47 50 53 56 59 62 65 69 72 75 78 81 84 87 90 93 97 100 103 106 109 112 115 118 122 125 128 131 134 137 140 143 147 150 153 156 157 159 162 165 168 171 175 178 181 184 187 190 193 196 200 203 206 209 212 215 218 221 224 228 231 234 237 240 243 246 249 253 256 259 262 265 268 271 274 277 281 284 287 290 293 296 299 302 306 309 312 313 315 318 321 324 327 330 334 337 340 343 346 349 352 355 359 362 365 368 371 374 377 380 383 387 390 393 396 399 402 405 408 412 415 418 421 424 427 430 433 437 440 443 446 449 452 455 458 461 465 468 469 471 474 477 480 483 486 490 493 496 499 502 505 508 511 514 518 521 524 527 530 533 536 539 543 546 549 552 555 558 561 564 567 571 574 577 580 583 586 589 592 596 599 602 605 608 611 614 617 620 624 625 627 630 633 636 639 642 645 649 652 655 658 661 664 667 670 674 677 680 683 686 689 692 695 698 702 705 708 711 714 717 720 723 727 730 733 736 739 742 745 748 751 755 758 761 764 767 770 773 776 780 781 783 786 789 792 795 798 801 804 808 811 814 817 820 823 826 829 833 836 839 842 845 848 851 854 857 861 864 867 870 873 876 879 882 886 889 892 895 898 901 904 907 911 914 917 920 923 926 929 932 935 936 939 942 945 948 951 954 957 960 964 967 970 973 976 979 982 985 988 992 995 998 1001 1004 1007 1010 1013 1017 1020 1023 1026 1029 1032 1035 1038 1041 1045 1048 1051 1054 1057 1060 1063 1066 1070 1073 1076 1079 1082 1085 1088 1091 1092 1094 1098 1101 1104 1107 1110 1113 1116 1119 1123 1126 1129 1132 1135 1138 1141 1144 1147 1151 1154 1157 1160 1163 1166 1169 1172 1176 1179 1182 1185 1188 1191 1194 1197 1201 1204 1207 1210 1213 1216 1219 1222 1225 1229 1232 1235 1238 1241 1244 1247 1248 1250 1254 1257 1260 1263 1266 1269 1272 1275 1278 1282 1285 1288 1291 1294 1297 1300 1303 1307 1310 1313 1316 1319 1322 1325 1328 1331 1335 1338 1341 1344 1347 1350 1353 1356 1360 1363 1366 1369 1372 1375 1378 1381 1384 1388 1391 1394 1397 1400 1403 1404 1406 1409 1413 1416 1419 1422 1425 1428 1431 1434 1438 1441 1444 1447 1450 1453 1456 1459 1462 1466 1469 1472 1475 1478 1481 1484 1487 1491 1494 1497 1500 1503 1506 1509 1512 1515 1519 1522 1525 1528 1531 1534 1537 1540 1544 1547 1550 1553 1556 1559 1560 1562 1565 1568 1572 1575 1578 1581 1584 1587 1590 1593 1597 1600 1603 1606 1609 1612 1615 1618 1621 1625 1628 1631 1634 1637 1640 1643 1646 1650 1653 1656 1659 1662 1665 1668 1671 1675 1678 1681 1684 1687 1690 1693 1696 1699 1703 1706 1709 1712 1715 1716 1718 1721 1724 1728 1731 1734 1737 1740 1743 1746 1749 1752 1756 1759 1762 1765 1768 1771 1774 1777 1781 1784 1787 1790 1793 1796 1799 1802 1805 1809 1812 1815 1818 1821 1824 1827 1830 1834 1837 1840 1843 1846 1849 1852 1855 1858 1862 1865 1868 1871 1872 1874 1877 1880 1883 1887 1890 1893 1896 1899 1902 1905 1908 1911 1915 1918 1921 1924 1927 1930 1933 1936 1940 1943 1946 1949 1952 1955 1958 1961 1965 1968 1971 1974 1977 1980 1983 1986 1989 1993 1996 1999 2002 2005 2008 2011 2014 2018 2021 2024 2027 2028 2030 2033 2036 2039 2042 2046 2049 2052 2055 2058 2061 2064 2067 2071 2074 2077 2080 2083 2086 2089 2092 2095 2099 2102 2105 2108 2111 2114 2117 2120 2124 2127 2130 2133 2136 2139 2142 2145 2148 2152 2155 2158 2161 2164 2167 2170 2173 2177 2180 2183 2184 2186 2189 2192 2195 2198 2202 2205 2208 2211 2214 2217 2220 2223 2226 2230 2233 2236 2239 2242 2245 2248 2251 2255 2258 2261 2264 2267 2270 2273 2276 2279 2283 2286 2289 2292 2295 2298 2301 2304 2308 2311 2314 2317 2320 2323 2326 2329 2332 2336 2339 2340 2342 2345 2348 2351 2354 2357 2361 2364 2367 2370 2373 2376 2379 2382 2385 2389 2392 2395 2398 2401 2404 2407 2410 2414 2417 2420 2423 2426 2429 2432 2435 2439 2442 2445 2448 2451 2454 2457 2460 2463 2467 2470 2473 2476 2479 2482 2485 2488 2492 2495 2496 2498 2501 2504 2507 2510 2513 2516 2520 2523 2526 2529 2532 2535 2538 2541 2545 2548 2551 2554 2557 2560 2563 2566 2569 2573 2576 2579 2582 2585 2588 2591 2594 2598 2601 2604 2607 2610 2613 2616 2619 2622 2626 2629 2632 2635 2638 2641 2644 2647 2651 2652 2654 2657 2660 2663 2666 2669 2672 2675 2679 2682 2685 2688 2691 2694 2697 2700 2704 2707 2710 2713 2716 2719 2722 2725 2729 2732 2735 2738 2741 2744 2747 2750 2753 2757 2760 2763 2766 2769 2772 2775 2778 2782 2785 2788 2791 2794 2797 2800 2803 2806 2807 2810 2813 2816 2819 1002 1005 1008 1011 1014 1018 1021 1024 1027 1030 1033 1036 1039 1042 1046 1049 1052 1055 1058 1061 1064 1067 1071 1074 1077 1080 1083 1086 1089 1093 1095 1099 1102 1105 1108 1111 1114 1117 1120 1124 1127 1130 1133 1136 1139 1142 1145 1148 1152 1155 1158 1161 1164 1167 1170 1173 1177 1180 1183 1186 1189 1192 1195 1198 1202 1205 1208 1211 1214 1217 1220 1223 1226 1230 1233 1236 1239 1242 1245 1249 1251 1255 1258 1261 1264 1267 1270 1273 1276 1279 1283 1286 1289 1292 1295 1298 1301 1304 1308 1311 1314 1317 1320 1323 1326 1329 1332 1336 1339 1342 1345 1348 1351 1354 1357 1361 1364 1367 1370 1373 1376 1379 1382 1385 1389 1392 1395 1398 1401 1405 1407 1410 1414 1417 1420 1423 1426 1429 1432 1435 1439 1442 1445 1448 1451 1454 1457 1460 1463 1467 1470 1473 1476 1479 1482 1485 1488 1492 1495 1498 1501 1504 1507 1510 1513 1516 1520 1523 1526 1529 1532 1535 1538 1541 1545 1548 1551 1554 1557 1561 1563 1566 1569 1573 1576 1579 1582 1585 1588 1591 1594 1598 1601 1604 1607 1610 1613 1616 1619 1622 1626 1629 1632 1635 1638 1641 1644 1647 1651 1654 1657 1660 1663 1666 1669 1672 1676 1679 1682 1685 1688 1691 1694 1697 1700 1704 1707 1710 1713 1717 1719 1722 1725 1729 1732 1735 1738 1741 1744 1747 1750 1753 1757 1760 1763 1766 1769 1772 1775 1778 1782 1785 1788 1791 1794 1797 1800 1803 1806 1810 1813 1816 1819 1822 1825 1828 1831 1835 1838 1841 1844 1847 1850 1853 1856 1859 1863 1866 1869 1873 1875 1878 1881 1884 1888 1891 1894 1897 1900 1903 1906 1909 1912 1916 1919 1922 1925 1928 1931 1934 1937 1941 1944 1947 1950 1953 1956 1959 1962 1966 1969 1972 1975 1978 1981 1984 1987 1990 1994 1997 2000 2003 2006 2009 2012 2015 2019 2022 2025 2029 2031 2034 2037 2040 2043 2047 2050 2053 2056 2059 2062 2065 2068 2072 2075 2078 2081 2084 2087 2090 2093 2096 2100 2103 2106 2109 2112 2115 2118 2121 2125 2128 2131 2134 2137 2140 2143 2146 2149 2153 2156 2159 2162 2165 2168 2171 2174 2178 2181 2185 2187 2190 2193 2196 2199 2203 2206 2209 2212 2215 2218 2221 2224 2227 2231 2234 2237 2240 2243 2246 2249 2252 2256 2259 2262 2265 2268 2271 2274 2277 2280 2284 2287 2290 2293 2296 2299 2302 2305 2309 2312 2315 2318 2321 2324 2327 2330 2333 2337 2341 2343 2346 2349 2352 2355 2358 2362 2365 2368 2371 2374 2377 2380 2383 2386 2390 2393 2396 2399 2402 2405 2408 2411 2415 2418 2421 2424 2427 2430 2433 2436 2440 2443 2446 2449 2452 2455 2458 2461 2464 2468 2471 2474 2477 2480 2483 2486 2489 2493 2497 2499 2502 2505 2508 2511 2514 2517 2521 2524 2527 2530 2533 2536 2539 2542 2546 2549 2552 2555 2558 2561 2564 2567 2570 2574 2577 2580 2583 2586 2589 2592 2595 2599 2602 2605 2608 2611 2614 2617 2620 2623 2627 2630 2633 2636 2639 2642 2645 2648 2653 2655 2658 2661 2664 2667 2670 2673 2676 2680 2683 2686 2689 2692 2695 2698 2701 2705 2708 2711 2714 2717 2720 2723 2726 2730 2733 2736 2739 2742 2745 2748 2751 2754 2758 2761 2764 2767 2770 2773 2776 2779 2783 2786 2789 2792 2795 2798 2801 2804 2808 2811 2814 2817 2820 101 104 107 110 113 116 119 123 126 129 132 135 138 141 144 148 151 154 158 160 163 166 169 172 176 179 182 185 188 191 194 197 201 204 207 210 213 216 219 222 225 229 232 235 238 241 244 247 250 254 257 260 263 266 269 272 275 278 282 285 288 291 294 297 300 303 307 310 314 316 319 322 325 328 331 335 338 341 344 347 350 353 356 360 363 366 369 372 375 378 381 384 388 391 394 397 400 403 406 409 413 416 419 422 425 428 431 434 438 441 444 447 450 453 456 459 462 466 470 472 475 478 481 484 487 491 494 497 500 503 506 509 512 515 519 522 525 528 531 534 537 540 544 547 550 553 556 559 562 565 568 572 575 578 581 584 587 590 593 597 600 603 606 609 612 615 618 621 626 628 631 634 637 640 643 646 650 653 656 659 662 665 668 671 675 678 681 684 687 690 693 696 699 703 706 709 712 715 718 721 724 728 731 734 737 740 743 746 749 752 756 759 762 765 768 771 774 777 782 784 787 790 793 796 799 802 805 809 812 815 818 821 824 827 830 834 837 840 843 846 849 852 855 858 862 865 868 871 874 877 880 883 887 890 893 896 899 902 905 908 912 915 918 921 924 927 930 933 937 940 943 946 949 952 955 958 961 965 968 971 974 977 980 983 986 989 993 996 999 1003 1006 1009 1012 1015 1019 1022 1025 1028 1031 1034 1037 1040 1043 1047 1050 1053 1056 1059 1062 1065 1068 1072 1075 1078 1081 1084 1087 1090 1096 1100 1103 1106 1109 1112 1115 1118 1121 1125 1128 1131 1134 1137 1140 1143 1146 1149 1153 1156 1159 1162 1165 1168 1171 1174 1178 1181 1184 1187 1190 1193 1196 1199 1203 1206 1209 1212 1215 1218 1221 1224 1227 1231 1234 1237 1240 1243 1246 1252 1256 1259 1262 1265 1268 1271 1274 1277 1280 1284 1287 1290 1293 1296 1299 1302 1305 1309 1312 1315 1318 1321 1324 1327 1330 1333 1337 1340 1343 1346 1349 1352 1355 1358 1362 1365 1368 1371 1374 1377 1380 1383 1386 1390 1393 1396 1399 1402 1408 1411 1415 1418 1421 1424 1427 1430 1433 1436 1440 1443 1446 1449 1452 1455 1458 1461 1464 1468 1471 1474 1477 1480 1483 1486 1489 1493 1496 1499 1502 1505 1508 1511 1514 1517 1521 1524 1527 1530 1533 1536 1539 1542 1546 1549 1552 1555 1558 1564 1567 1570 1574 1577 1580 1583 1586 1589 1592 1595 1599 1602 1605 1608 1611 1614 1617 1620 1623 1627 1630 1633 1636 1639 1642 1645 1648 1652 1655 1658 1661 1664 1667 1670 1673 1677 1680 1683 1686 1689 1692 1695 1698 1701 1705 1708 1711 1714 1720 1723 1726 1730 1733 1736 1739 1742 1745 1748 1751 1754 1758 1761 1764 1767 1770 1773 1776 1779 1783 1786 1789 1792 1795 1798 1801 1804 1807 1811 1814 1817 1820 1823 1826 1829 1832 1836 1839 1842 1845 1848 1851 1854 1857 1860 1864 1867 1870 1876 1879 1882 1885 1889 1892 1895 1898 1901 1904 1907 1910 1913 1917 1920 1923 1926 1929 1932 1935 1938 1942 1945 1948 1951 1954 1957 1960 1963 1967 1970 1973 1976 1979 1982 1985 1988 1991 1995 1998 2001 2004 2007 2010 2013 2016 2020 2023 2026 2032 2035 2038 2041 2044 2048 2051 2054 2057 2060 2063 2066 2069 2073 2076 2079 2082 2085 2088 2091 2094 2097 2101 2104 2107 2110 2113 2116 2119 2122 2126 2129 2132 2135 2138 2141 2144 2147 2150 2154 2157 2160 2163 2166 2169 2172 2175 2179 2182 2188 2191 2194 2197 2200 2204 2207 2210 2213 2216 2219 2222 2225 2228 2232 2235 2238 2241 2244 2247 2250 2253 2257 2260 2263 2266 2269 2272 2275 2278 2281 2285 2288 2291 2294 2297 2300 2303 2306 2310 2313 2316 2319 2322 2325 2328 2331 2334 2338 2344 2347 2350 2353 2356 2359 2363 2366 2369 2372 2375 2378 2381 2384 2387 2391 2394 2397 2400 2403 2406 2409 2412 2416 2419 2422 2425 2428 2431 2434 2437 2441 2444 2447 2450 2453 2456 2459 2462 2465 2469 2472 2475 2478 2481 2484 2487 2490 2494 2500 2503 2506 2509 2512 2515 2518 2522 2525 2528 2531 2534 2537 2540 2543 2547 2550 2553 2556 2559 2562 2565 2568 2571 2575 2578 2581 2584 2587 2590 2593 2596 2600 2603 2606 2609 2612 2615 2618 2621 2624 2628 2631 2634 2637 2640 2643 2646 2649 2656 2659 2662 2665 2668 2671 2674 2677 2681 2684 2687 2690 2693 2696 2699 2702 2706 2709 2712 2715 2718 2721 2724 2727 2731 2734 2737 2740 2743 2746 2749 2752 2755 2759 2762 2765 2768 2771 2774 2777 2780 2784 2787 2790 2793 2796 2799 2802 2805 2809 2812 2815 2818 2781 2756 2728 2703 2678 2650 2625 2597 2572 2544 2519 2491 2466 2438 2413 2388 2360 2335 2307 2282 2254 2229 2201 2176 2151 2123 2098 2070 2045 2017 1992 1964 1939 1914 1886 1861 1833 1808 1780 1755 1727 1702 1674 1649 1624 1596 1571 1543 1518 1490 1465 1437 1412 1387 1359 1334 1306 1281 1253 1228 1200 1175 1150 1122 1097 1069 1044 1016 102 105 108 111 114 117 120 124 127 130 133 136 139 142 145 149 152 155 161 164 167 170 173 177 180 183 186 189 192 195 198 202 205 208 211 214 217 220 223 226 230 233 236 239 242 245 248 251 255 258 261 264 267 270 273 276 279 283 286 289 292 295 298 301 304 308 311 317 320 323 326 329 332 336 339 342 345 348 351 354 357 361 364 367 370 373 376 379 382 385 389 392 395 398 401 404 407 410 414 417 420 423 426 429 432 435 439 442 445 448 451 454 457 460 463 467 473 476 479 482 485 488 492 495 498 501 504 507 510 513 516 520 523 526 529 532 535 538 541 545 548 551 554 557 560 563 566 569 573 576 579 582 585 588 591 594 598 601 604 607 610 613 616 619 622 629 632 635 638 641 644 647 651 654 657 660 663 666 669 672 676 679 682 685 688 691 694 697 700 704 707 710 713 716 719 722 725 729 732 735 738 741 744 747 750 753 757 760 763 766 769 772 775 778 785 788 791 794 797 800 803 806 810 813 816 819 822 825 828 831 835 838 841 844 847 850 853 856 859 863 866 869 872 875 878 881 884 888 891 894 897 900 903 906 909 913 916 919 922 925 928 931 934 938 941 944 947 950 953 956 959 962 966 969 972 975 978 981 984 987 990 994 997 1000 991 963 910 885 860 832 807 779 754 726 701 673 648 623 595 570 542 517 489 464 436 411 386 358 333 305 280 252 227 199 174 146 121 Hokkaido Iwate Miyagi Ibaraki Aomori Fukushima Chiba 0 Reproduction index by Aida(1978) The criteria established by JSCE(2002) 0.95<K<1.05 and κ<1.45 Number of the locations Observed tsunami height at location i Calculated tsunami height at location i Fig.3 Comparison of the flooding height and run-up height 626
(a) Location of the tide records (b) Comparison data - Part1 - (c) Comparison data Part2 (d) Comparison data Part3 - Fig.4 Comparison of the tide record 627
ー 1m ー 2m ー 3m ー 4m ー 5m ー 6m 6m over 以上は6m 非表示 Oshika Approx. 5.3m ー 6m ー 5m 4m ー 3m ー 2m ー 1m (a) Crustal movement in horizontal ( Left : Calculated, Right : Observed ) over 1.5m Oshika Subsidence at Approx. 1.2m (b) Crustal movement in vertical; Subsidence ( Left : Calculated, Right : Observed ) Fig.5 Comparison of the crustal movement in the land area 628
(a) Crustal movement in horizontal (Red: Calculated, Blue: Observed ) (b) Crustal movement in vertical (Red : Calculated, Blue : Observed ) Fig.6 Comparison of the crustal movement in the marine area 629
Aomori Iwate Miyagi Fukushima Ibaraki Chiba Fig.7 Comparison of the inundated area CONCLUSIONS For the purpose of investigating the mechanisms of the earthquake and tsunami of the Great East Japan Earthquake on March 11, 2011, we carried out a tsunami inversion analysis. We focused attention on the a) tide record, b) flooding height and run-up height, c) crustal movement and d) inundated area over a wide area (form Hokkaido to Chiba). The proposed source model with a magnitude (Mw) of 9.1 consists of mutually independent 80 blocks, and each block has a different fault slip amount. The maximum fault slip amount which is located near the trench axis is 56.7m. As a result, we confirmed that the observed tsunami data, especially the four parameters described above, are reproduced quite accurately via the model in a well balanced manner. We assumed that the rupture start time and the duration time are constant for all regions in this inversion model. However these two parameters could be effective in improving the tsunami source model. We think that the investigation of the effect of these parameters is a future task. In addition to the aforementioned parameters, the splay fault and landslide induced by the earthquake could also be effective in improving the model. REFERENCES Aida, I. (1978). Reliability of a tsunami source model derived from fault parameters. Journal of Physics of Earth, Vol. 26, 57-73. Annaka, T., Ohta, K., Motegi, H., Yoshida, I., Takao, M. and Soraoka, H. (1999). Tsunami inversion based on the shallow water theory. Proceedings of Coastal Engineering, JSCE, Vol. 46, 341-345 (in Japanese). Fujii, Y., Satake, K., Sakai, S., Shinohara, M. and Kanazawa, T. (2011). Tsunami source of the 2011 off the Pacific coast of Tohoku, Japan earthquake. Earth Planets Space, Vol. 63, No. 7, 815-820. Geospatial Information Authority of Japan (2011a). The2011 off the Pacific coast of Tohoku Earthquake : Crustal deformation and fault model. 630
http://www.gsi.go.jp/cais/topic110421-index-e.html. Geospatial Information Authority of Japan (2011b) The map of 1/100,000 inundation area, http://www.gsi.go.jp/kikaku/kikaku60003.html (in Japanese). The Headquarters for Earthquake Research Promotion (2002). Long Term Evaluation of Earthquake Activity from offing of Sanriku to offing of Bousou. http://www.jishin.go.jp/main/chousa/02jul_sanriku/index.htm (in Japanese) Japan Coast Guard (2011) Information on the 2011 off the Pacific Coast of Tohoku Earthquake. http://www1.kaiho.mlit.go.jp/gijutsukokusai/jishin/11tohoku/index.html Japan Meteorological Agency (2011) Real-time tidal observation data. http://www1.kaiho.mlit.go.jp/kankyo/tide/real_time_tide/sel/index_e.htm Japan Society of Civil Engineers (2002). Tsunami assessment method for nuclear power plants in Japan. The Tsunami Evaluation Subcommittee, Nuclear Civil Engineering Committee, JSCE (Japan Society of Civil Engineers), translated into English 2006. Manshinha, L. and Smylie, D. E. (1971). The displacement field of inclined faults. Bulletin of the Seismological Society of America, Vol. 61, No. 5, 1433 1440. Ports and Harbours Bureau, Ministry of Land Infrastructure, Transport and Tourism (2011), NOWPHAS, Nationwide Ocean Wave information network for Ports and HArbourS, http://www.mlit.go.jp/kowan/nowphas/index_eng.html National Oceanic and Atmospheric Administration (2011). National Data Buoy Center, http://nctr.pmel.noaa.gov/dart/ Tanioka, Y. (2011). On March 11, 2011 off the Pacific coast of Tohoku (M9.0). http://www.sci.hokudai.ac.jp/isv/ev-news-flash/#a-04 (in Japanese). Earthquake Research Institute, University of Tokyo (2011). 2011 Tohoku Earthquake, http://outreach.eri.u-tokyo.ac.jp/eqvolc/201103_tohoku/eng/#sealevel The 2011 Tohoku Earthquake Tsunami Joint Survey Group (2011). The 2011 off the Pacific coast of Tohoku Earthquake Tsunami Information. http://www.coastal.jp/ttjt/, release 20110621. 631