DOCSLIB.ORG

Possibility of a Great Earthquake in the Tokai District, Central Japan

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Possibility of a Great Earthquake in the Tokai District, Central Japan J. Phys. Earth, 25, Suppl., S 219-S 230, 1977 POSSIBILITY OF A GREAT EARTHQUAKE IN THE TOKAI DISTRICT, CENTRAL JAPAN Tokuji UTSU Departmentof EarthSciences, Faculty of Science, Nagoya University, Nagoya,Japan (ReceivedMarch 25, 1977) The Tokai districthas been consideredto be one of the probablesites of great interplateearthquakes in the near future.This idea isbased on the time seriesof historicalgreat earthquakes and the fairlyhigh rateof crustalmovement observed in thisregion for more than 80 years. The lastgreat earthquake was the Ansei earthquakeof 1854 (M=8.4). The westernhalf of the sourceregion of thisearth- quake rupturedagain in the 1944 Tonankai earthquake,but the easternhalf, i.e., theTokai district,remain unrupturedfor 122 years.The recurrencetime intervalof greatearthquakes in thisregion estimated from historicalearthquakes, topograph- icaland geologicalevidences, observed strain rates, the rateof plateconvergence, etc.varies from 120 yearsto more than 600 years. There are severalobservations which may suggestthat thisregion has alreadybeen in the long-termprecursory stage.However, itis questionable that these observations represent real precursors to the futureTokai earthquake. It seems possiblethat the next greatearthquake will occur south of the Izu Peninsula and will release the strain in the Tokai dis- trict. In any case, the Tokai district should be watched carefully for every con- ceivable precursors in order to make a successful prediction. 1. Introduction In the pastseveral years, the possibilityof a greatinterplate earthquake in the Tokai districthas been much discussedby Japanese earth scientists.The Tokai districtis a southern coastalregion of centralJapan (ShizuokaPrefecture and its vicinity)near thenorthern tip of the PhilippineSea plate(Fig. 1, rightbottom). In 1969,the Coordinating Committee forEarthquake Prediction,Japan (CCEP, Prof.T. Hagiwara, chairman) designatedthis region as 'theregion of specifiedobservation' for the follwing reasons. (1)Japan's history shows repeatedoccurrences of great earthquakesin thisregion. The lastone was theAnsei earthquakeof 1854 (M=8.4). (2)The analysisof two triangulationsurveys in 1886-87 and 1954-56 indicatesthat thisregion has been compressedconsiderably to the northwest(HARADA and IZAWA, 1969). This result,together with fairlyrapid subsidence of thewest coastof Suruga Bay observedsince 1889 (GEOGRAPHICAL SURVEY INSTITUTE,1970), seems to indicate the accumulationof considerableamount of strainin thisregion, which must be releasedby the futureTokai earthquake(MOGI, 1970). In 1973,the problem of the Tokai earthquakereceived much public attention through newspaperreports of the researchesby ANDO (1975a),RIKITAKE (1974),and S 219 S 220 T. UTSU others.In the background,there was a factthat the Nemuro-oki earthquakeof June 17, 1973 (M=7.4) occurredjust within one of the regionsof specifiedobservation designatedby the CCEP in 1970. The reasonsfor the designationwere very similar to the case of the Tokai district.In 1974,the CCEP upgraded the Tokai districtto 'theregion of intensifiedobservation .' In 1976,documents reportingthe effects of theAnsei earthquake along the coast of Suruga Bay were found by chance (EARTHQUAKE RESEARCH INSTITUTE,1977). The documents indicatethat the rupturezone of the Ansei earthquakeextended to the northernend of Suruga Bay (HATORI, 1976;ISHIBASHI, 1976). The importance of thisfact pointed out by Ishibashishocked the local people. The anomalous uplift in the Izu Peninsulasince 1975 (e.g.,TSUMURA, 1977)has alsobeen watched in re- lationto theTokai earthquake.Near theend of 1976,the GeodeticCouncil of Japan (Prof.T. Nagata, chairman) recommended the intensificationof various kinds of observationsand surveysin the Tokai districtto the government of Japan. The recommendation alsoincludes rapid collection of data by a monitoringcenter on the 24-hr basisand organizationof a specialcommittee forevaluating anomalous phenomena which may be short-termprecursors to the Tokai earthquake. This paper reviews the main informationand studiesin connectionwith the predictionof the Tokai earthquakeavailable as of January, 1977. The materials presentedto theCCEP's subcommitteefor the Tokai district(Prof. T. Asada, chair- man) were very usefulin preparingthis paper. 2. Tectonic Situation There is general agreement that the northern part of the Philippine Sea plate moving to the northwest relative to the Eurasia plate underthrusts at the Nankai trough. The great earthquakes along the Nankai trough are caused by the rebound of the compressed crust of the Japanese Islands (FITCH and SCHOLZ, 1971; KANAMORI, 1972; ANDO, 1975a, b). Near its eastern end, the Nankai trough bends to the north and enters into Suruga Bay. This part of the trough is sometimes called the Suruga trough. To the east, the Sagami trough defines the boundary of the two plates. The plate boundary is obscured between the Suruga and Sagami troughs. Collision of the Izu Peninsula with Honshu Island forms a zone of deformation around Mt. Fuji. The relative motion of the Philippine Sea plate to the Eurasia plate has been discussed by SENO (1976). According to his calculation, the pole of the relative motion is located at 45.3±3.7°N, 150.2±5.5°E near the southern Kurile Islands. The convergence rate at the Tokai district is about 3cm/yeat. ANDO (1975b) con- structed geodetic models for the fault dislocation of the 1944 Tonankai, 1854 Ansei, and 1707 Hoei earthquakes. The estimated dislocation for the 1944 and 1854 earth- quakes is 4m, and for the 1707 earthquake 8m. If the average dislocation is 4m at the Tokai district, the recurrence time will be about 130years. Since the part of the Philippine Sea plate near the Tokai district is not a simple oceanic plate, the pattern of the plate consumption may be complicated. As explained Possibility of a Great Earthquake in the Tokai District, Central Japan S 221 in the next section,source regions of some great earthquakes near the Tokai district seem to extend beyond the Nankai trough. Tectonic lineshave been assumed south of the Izu Peninsula as indicatedby broken linesin Fig.1 (rightbottom) along which thrust faultingmay take place (ISHIBASHI,1976; AOKI, 1977). However, no direct geophysical or geologicalevidence has been found to support such a hypothesis of multiple plateboundaries. 3. HistoricalEarthquakes Source regions(rupture zones) of largehistorical earthquakes along the Nankai and Sagami troughsare shown in Fig. 1. Except forthe 1923, 1944,and 1946 earth- quakes,the sourceregions have been estimatedfrom the descriptionof macroseismic effects,land deformations,and tsunamisin the historicalrecords. For olderevents, Fig.1. Historicalearthquakes along the Nankai and Sagami troughs,and volcaniceruptions probably related to them. Map scale,1:15,000,000. S 222 T. UTSU the delineationof the sourceregions is more speculativedue to fewerhistorical ma- terials.The years of greatearthquakes having magnitude 8 or more are indicated by largenumerals. There are 14 greatearthquakes occurring in nine epochslabeled [1],[2],..., [9]. Medium numerals in dashed ellipsesrepresent the approximate positionof earthquakesof magnitude 7 to 7.5. The dashed ellipsein epoch [9]indi- catesthe probable source region of the Tokai earthquakenow generallyassumed (e.g.,ISHIBASHI, 1976). Itis seen that the westernhalf of the sourceregion of the 1854 earthquakerup- turedagain in the 1944 earthquake,but the easternhalf remains unruptured for 122 years. The faultingof the 1707 earthquakealso extended into Suruga Bay, since Cape Omaezaki upheaved by about 1m at the time of the earthquake.However, it isnot certainthat the faultingreached the northernend of Suruga Bay as in thecase of the 1854 earthquake. It seems unlikelythat the source regionsof the 1605 Keicho and 1498 Meio earthquakescovered the Suruga Bay area. The shakingwas not so strongand no evidence of land deformationwas reportedin the Tokai district.However, the tsunamiswere very strongalong the Tokai coast. The tsunamiswere alsovery high in the Sagami Bay area and the Boso Peninsula. Hachijo Islandwas attackedby largetsunamis after the both earthquakes.Hachijo volcanoerupted 9 months after the 1605 earthquake.The othereruptions of Hachijo known in thehistory occurred in 1487, 1518,and 1522-23. These were fairlyclose to the 1498 earthquake. The 1605 earthquakehas been consideredto be two eventsoccurring simultaneously off Nankaido and offthe Boso Peninsula.However, the strongtsunami along the Tokai coastsuggests a possibilitythat the faultslipped slowly off the Tokai district.The sourceregion of the 1498 earthquakeshown in Fig.1 isthe one proposedby HATORI (1976).By studyingthe remainsof ancientboring shells, FUKUTOMI (1934,1938) inferredthat the southern Izu Peninsulaand Niijimaand ShikineIslands uplifted by a few metersseveral hundred years ago. The uplift maycorrespond to the 1498or 1605 earthquake. Itis likely that the faulting of the 1096Eicho earthquakeextended into Suruga Bay,because the tsunami was strongon thebay coast,though no materialsindicating theuplift of the coasthave been found. No directinformation is available indicating that the rupturezones of the 887 and 684 earthquakesreached to the Tokai district.The 887 earthquakewas a very big one, and itwas accompanied by a largeearthquake near Nagano (about 150km north of Mt. Fuji)on the same day. The largeeruptions of Mt. Fuji occurred in 1707, one and half months afterthe greatearthquake, and in 800-01 and 864-66. These eventsare marked in Fig. 1. Only three
Load more

Recommended publications
  • Tokai Earthquake Preparedness in Shizuoka Prefecture, Japan
    Tokai Earthquake Preparedness in Shizuoka Prefecture, Japan April 2010 Shizuoka Prefecture This document was originally created and published by Shizuoka Prefecture in Japan. English translation was provided by Yohko Igarashi, Visiting Scientist, ITIC, with the kind acceptance of Shizuoka Prefecture. For Educational and Non-Profit Use Only ! -,2#,21 1. Tokai Earthquake ዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉ 1 (1) Tokai Earthquake ጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟ 1 (2) Basis of the Occurrence of Tokai Earthquake ጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟ 2 Fujikawa-kako Fault ZoneዋTonankaiNankai Earthquake ጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟ 3 2. Estimated Damageዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉ 4 3. Operation of Earthquake Preparedness ዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉ 7 4. Monitoring System for Tokai Earthquake ዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉ 10 (1) Governmental System of Earthquake Research ጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟ 10 (2) Observation Network for Earthquake Prediction in Shizuoka Prefecture ጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟ 11 5. Responses to the Issuance of “Information about Tokai Earthquake” ዉዉዉዉዉዉዉዉዉዉዉዉዉ 12 6. Working on Effective Disaster Managementዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉዉ 14 (1) Disaster Management System in Shizuoka Prefecture ጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟ 14 (2) Community Support Staffs in Local Disaster Prevention Bureau ጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟ 14 (3) Establishing Permanent Disaster Management Headquarters Facilitiesጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟ 15 (4) Advanced Information Network System ጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟጟ
    [Show full text]
  • Izu Peninsula Geopark Promotion Council
    Contents A. Identification of the Area ........................................................................................................................................................... 1 A.1 Name of the Proposed Geopark ........................................................................................................................................... 1 A.2 Location of the Proposed Geopark ....................................................................................................................................... 1 A.3 Surface Area, Physical and Human Geographical Characteristics ....................................................................................... 1 A.3.1 Physical Geographical Characteristics .......................................................................................................................... 1 A.3.2 Human Geographical Charactersitics ........................................................................................................................... 3 A.4 Organization in charge and Management Structure ............................................................................................................. 5 A.4.1 Izu Peninsula Geopark Promotion Council ................................................................................................................... 5 A.4.2 Structure of the Management Organization .................................................................................................................. 6 A.4.3 Supporting Units/ Members
    [Show full text]
  • Explore Shizuoka Explore the Spectacular Natural Environment, Authentic Japanese Culture, Unique History and Renowned Cuisine Of
    Explore the spectacular natural environment, authentic Japanese culture, unique history and renowned cuisine of the majestic home of Mount Fuji. Exploreshizuoka.com NATURAL BEAUTY, ON LAND AND SEA From the iconic Mount Fuji in the north to 500km of spectacular Pacific coastline in the south, Shizuoka is a region of outstanding natural beauty, with highlands, rivers and lakes giving way to the white sand beaches and volcanic landscapes of the Izu Peninsula. And all this just one hour from Tokyo by shinkansen (bullet train). Okuoikojo Station MOUNTAINS, FORESTS AND FALLS At 3,776m high, the majestic “Fuji-san” is Japan’s best-known symbol with shrines paying homage to the mountain and paintings illustrating its beauty. Designated a UNESCO World Cultural Heritage Site in 2013, the climbing season runs from July to early September. Shizuoka’s central area is dominated by deeply forested mountains that stand over 800 m in height, tea plantations and beautiful waterfalls, such as the Shiraito Falls which, along with the 25m Joren Falls on the Izu Peninsula, is ranked among the 100 most beautiful waterfalls in Japan. The Seven Waterfalls of Kawazu are surrounded by a thick forest of pines, cedars and bamboo with a walking path taking you to all seven in roughly one hour. For a unique and unforgettable experience, visitors can take the historic Oigawa steam railway to visit the beautiful “Dream Suspension Bridge” across the Sumatakyo Gorge. THE IZU PENINSULA Surrounded by ocean on three sides, the Izu Peninsula was designated a UNESCO Global Geopark in 2018. Twenty million years of shifting undersea volcanoes created its dramatic landscapes and natural hot springs.
    [Show full text]
  • Simulation of Recurring Earthquakes Along the Nankai Trough and Their
    JOURNAL OF GEOPHYSICAL RESEARCH: SOLID EARTH, VOL. 118, 4127–4144, doi:10.1002/jgrb.50287, 2013 Simulation of recurring earthquakes along the Nankai trough and their relationship to the Tokai long-term slow slip events taking into account the effect of locally elevated pore pressure and subducting ridges Fuyuki Hirose1 and Kenji Maeda 1 Received 21 February 2013; revised 8 July 2013; accepted 9 July 2013; published 6 August 2013. [1] Many earthquakes of moment magnitudes greater than 8 associated with subduction of the Philippine Sea plate under Japan have occurred along the Nankai trough with a recurrence interval of 90–150 years. A large-scale rupture of the Tokai fault segment is believed to be imminent because that segment did not rupture during the most recent Tonankai earthquake in 1944. Recurring long-term slow slip events (LSSEs) have recently been observed in the Tokai region. To investigate the current stress state in the Tokai region, we numerically simulated earthquake cycles using a three-dimensional model consisting of triangular cells based on the rate- and state-dependent friction law. Our numerical simulations successfully modeled the Tokai segment not ruptured during the 1944 Tonankai earthquake as well as the recurring LSSEs in the Tokai region. We found that a large characteristic displacement (L) and effective normal stress (σ) in areas of subducted ridges are essential to avoid rupture of the Tokai segment during the 1944 Tonankai earthquake. We also demonstrated that we can reproduce the recurring LSSEs by assigning low values of σ and L to the area beneath Lake Hamana without introducing a velocity-strengthening friction law at high slip rate.
    [Show full text]
  • 1 EFFECT of GROUND SUBSIDENCE DUE to CRUSTAL MOVEMENT on BEACH CHANGES on OMAEZAKI COAST, JAPAN Nobuaki Iwazaki1, Toshiro San-Na
    EFFECT OF GROUND SUBSIDENCE DUE TO CRUSTAL MOVEMENT ON BEACH CHANGES ON OMAEZAKI COAST, JAPAN Nobuaki Iwazaki1, Toshiro San-nami2, Takaaki Uda3 and Toshinori Ishikawa3 Shoreline changes along the coasts between the Tenryu River mouth and Omaezaki Point facing the Pacific Ocean were investigated using aerial photographs. Beach has been eroded on the coast located near the east end of the coastline far from the river mouth. Although beach erosion on the nearby coasts to the Tenryu River mouth was triggered by the decrease in fluvial sand supply and the obstruction of longshore sand transport by a port breakwater, beach erosion on a coast far from the river mouth was due to the effect of ground subsidence associated with crustal movement, and partly due to the effect of windblown sand. Keywords: Ground subsidence; crustal movement; beach erosion; longshore sand transport INTRODUCTION The coastline west and east of the Tenryu River has been formed as a fluvial fan of the Tenryu River (Fig. 1). Because the coast is part of a river delta, beach changes due to the decrease in sand supply from the river have occurred mainly around the river mouth in recent years, and various measures have been taken, including sand bypassing from dams in upstream basins (Miyahara et al., 2010). However, severe beach erosion has been occurring on the Omaezaki coast located 40 km east of the Tenryu River mouth and near the east end of an arc-shaped shoreline, even though the eastern shoreline closer to the river mouth has been stable. Difficulties have arisen in considering suitable countermeasures in this area because the exact causes of beach erosion have not been identified.
    [Show full text]
  • SHIZUOKA – Home of Mt. Fuji Delicious Seafood and Fish Products of SHIZUOKA
    SHIZUOKA – Home of Mt. Fuji Delicious Seafood and Fish products of SHIZUOKA 1 Shizuoka Located in the Center of Japan 138°E Sapporo○ S （ ） H Mt. FUJI 3776m Sendai ○ I Z ○Tokyo KyotoNagoya △ U Hiroshima ○ ○ 35°N ○ ○ Green tea, Melons Fukuoka Osaka O ○ SHIZUOKA Prefecture K A a Food & Agriculture s Fish(Tuna) Wasabi,Mandarin N O . 1 Industry(HQ) 2 • A varied coastline of 647 km and rich Area of marine resources brought in by the Japan Mt. Fuji Rainbow Current trout • Suruga Bay, which reaches a depth of Mt. Fuji 2,500 m, Japan’s deepest bay; Lake Numazu Dried fish, Yui deep-sea Hamana, where sea water and fresh Sakura fish Atami water mix; Izu Peninsula, full of rocky shrimps Dried fish shores and reefs; the Enshu-nada Coast, with vast sand dunes Shizuoka Tuna, young sardines, canned Yaizu seafood, Dried bonito, half- processed dried bonito, broth, food sauce, kamaboko, hanpen, eels, seared bonito slices, stewed Hamamatsu bonito, salted fish Eels, young guts Nishiizu sardines, lavers, Dried- Japanese salted littleneck clams, bonito puffer fish Higashiizu Dried fish, splendid alfonsinos 3 Positioning of the Fishing Industry in Shizuoka Prefecture 2013 Catch in major fishing ports in Japan Shizuoka Ranking Name of All Japan Prefecture in Japan Rank fishing Amount (million yen) Fisheries yield (2012) 225,934 (tons) 3 4,864,275 (tons) port Overall marine fisheries and fish 58.8 (million yen) 5 1,328.5 (million yen) 1 Fukuoka 43.9 farming (2012) Number of fishery operators (2008) 6,505 (persons) 11 221,908 (persons) 2 Yaizu 42.9 Volume of processed marine 171,232 (tons) 2 1,727,969 (tons) 3 Nagasaki 34.2 products (2012) 4 Nemuro 29.1 150 5 Choshi 27.0 129 (thousand tons) 100 50 26.7 22.6 20.9 19.8 19.7 17.3 15.8 15.3 15.0 0 北 長 静 三 青 宮 千 茨 鹿 愛 海 崎 岡 重 森 城 葉 城 児 媛 道 県 県 県 県 県 県 県 島 県 Chiba Mie Ibaraki Aomori Miyagi 県 Ehime Shizuoka Hokkaido Nagasaki Kagoshima Shizuoka Prefecture boasts the 3rd largest yield of all fisheries in Japan.
    [Show full text]
  • Port of Omaezaki in Tern a Tio N a L M Ultipurpo Se Term in a L Good Loc Ation At
    2016 PORT OF OMAEZAKI IN TERN A TIO N A L M ULTIPURPO SE TERM IN A L GOOD LOC ATION AT ASIAN AREA The natural marine ac c e s s is truly a gate way to the s e a. Omaezaki Port is at the entrance of Pacific Ocean-facing Suruga Bay and is a gateway to the sea with numerous shipping routes and easy marine access. Located almost midway between Tokyo and Osaka, Omaezaki Po rt lies within the pac ific belt zo ne linking Japan s industrial areas. In the background, this area maintains the production base for industrial products such as automobiles and musical instruments from Shizuoka Prefecture s western and c entral regio ns and is a leading trading po rt c entered o n freight. In c o o peratio n with Shimizu Po rt, Omaezaki Po rt is widening its func tio n as Shizuo ka Prefec ture s freight transpo rt c o mplex. THE HEA RT O F J A PA N PORT OF OMAEZAKI A base for transport networks by land, sea, and air In addition to excellent marine access, the implementation and maintenance of roads in the areas surrounding Omaezaki Port are rapidly progressing. Land access to major c ities has improved dramatic ally by the widening o f Route 150 to four lanes and by the opening of the Kanaya-Omaezaki connecting road. With the completion of the New Tomei Expressway and Mt. Fuji Shizuoka Airport, Omaezaki Port has c o nsequently further expanded its role as the hub of land, sea, and air transportation networks.
    [Show full text]
  • Stress Transfer in the Tokai Subduction Zone from the 2009 Suruga Bay Earthquake in Japan
    O-21 Stress transfer in the Tokai subduction zone from the 2009 Suruga Bay earthquake in Japan B. Enescu 1, S. Aoi 1*, W. Suzuki 1, Y. Asano 1, K. Obara 2,1, T. Kunugi 1 and K. Shiomi 1 1 National Research Institute for Earth Science and Disaster Prevention 2 The University of Tokyo * E-mail: [email protected] 1. Introduction In southwest Japan, megathrust earthquakes occur at intervals of 100-200 years (Ando, 1975) at the subduction of the Philippine Sea (PHS) plate beneath the Eurasian plate. The M-8-class earthquake seismogenic zone is divided into three segments: Nankai, Tonankai and Tokai. Two megathrust earthquakes ruptured the Tonankai and Nankai segments in 1944 and 1946, respectively; however the Tokai segment did not rupture at that time and is still in a locked state. In 2009, an Mw6.4 earthquake took place in Suruga Bay, within the PHS plate, close to the Tokai segment. In this study we investigate the impact of the stress changes caused by the recent Suruga Bay earthquake on the Tokai segment. 2. Earthquake relocations and the rupture process of the Suruga Bay mainshock The earthquake hypocenters of the Suruga Bay sequence (mainshock and aftershock activity) were precisely relocated by the double-difference method (Waldhauser and Ellsworth, 2000), using NIED’s Hi-net data. The relocation of earthquakes revealed a two-plane-shaped hypocentral distribution of aftershocks, indicating that the sequence occurred along two quasi-orthogonal faults, located in the southern (Fault I) and northern (Fault II) parts of the aftershock area. The mainshock hypocenter is located on Fault I.
    [Show full text]
  • Earthquake Disaster Prevention Guidebook
    Earthquake countermeasures document No.283-2014 Earthquake Disaster Prevention Guidebook BeBe PreparedPrepared Operating Closed Mondays, end-of-year holidays hours 9:00~16:00 (Dec. 28 – Jan. 4) Shizuoka Prefecture 5-9-1 Komagatadori, Aoi Ward, Shizuoka, 420-0042 Earthquake Disaster TEL. 054−251−7100 FAX. 054−251−7300 Prevention Center * Take care to enter the correct number. 備蓄食 2014.12 Unauthorized copying is prohibited. Printed using recycled paper. 備蓄食 Shizuoka Prefecture ガイドブック E.indd 1 15/01/14 16:36 Table of Contents 1 Learning from other earthquakes [Knowledge Section] 1) Previous Destructive Earthquakes Many earthquakes occur in Japan and its surrounding seas. 1. Learning from other earthquakes ............................................................................................ Great East Japan 1) Previous Destructive Earthquakes 1 Tsunami damage Great Kanto Earthquake Fire outbreak Earthquake ...................................................................................... 2) Magnitude (M) and Seismic Intensity 2 Dead: 15,885, missing: 2,632, 1923.9.1 M7.9 Dead and missing: 105,385. 2011.3.11 Mw9.0 injured: 6,148. (Current as of April 10, 2014) ............................................................... The damage caused by the earthquake was magnified by multiple fires that broke 2. Large-Scale Earthquake Prediction 3 The Great East Japan Earthquake was an inter-plate earthquake, like the out afterwards. Disaster was widespread, with over 370,000 households fully or Tokai earthquake expected to occur in the near future would be. At partially destroyed, burned, or washed away. A tsunami also struck Sagami Bay, 1) The Tokai Earthquake Theory .................................................................................................. 3 Mw9.0, it was the largest earthquake recorded in Japanese history. The with wave heights of 12m hitting Atami. earthquake resulted in a large-scale tsunami, which led to massive ..................................................................................
    [Show full text]
  • A Numerical Experiment on Ocean Circulations Forced by Seasonal Winds in Suruga Bay
    Coastal Marine Science 31(1): 30–39, 2007 A numerical experiment on ocean circulations forced by seasonal winds in Suruga Bay 1 2 3 Kiyoshi TANAKA *, Yutaka MICHIDA and Teruhisa KOMATSU 1 Center for Advanced Marine Research, Ocean Research Institute, The University of Tokyo *E-mail: [email protected] 2 Center for International Cooperation, Ocean Research Institute, The University of Tokyo 3 Department of Marine Bioscience, Ocean Research Institute, The University of Tokyo Received 8 June 2006; Accepted 15 September 2006 Abstract —We investigate influence of the seasonal variation in the wind field on water circulation in Suruga Bay by using a wind data set and a numerical ocean model. Counterclockwise vorticity is supplied around the bay mouth from the atmosphere into the ocean in January (winter) and April (spring), whereas clockwise vorticity is supplied in July (summer) and October (au- tumn). Corresponding to the change in the wind field, a counterclockwise circulation is generated at the sea surface around the bay mouth in January and April, whereas a clockwise circulation in July and October. Moreover, one or two weak circulations are generated to the north of the circulation. These circulations, which are quasi-geostrophic and strongly influenced by land and ocean bottom topography, are generated without effect of the Kuroshio current. Quasi-stagnant and convergent regions tend to appear in the surface layer in the eastern part of the bay, except for autumn. There is a possibility that the wind-driven circulations may play an important role in transport of floating materials, such as seagrass, from in and around the bay to the eastern part of the bay, where a large amount of seagrass has been observed both on the sea surface and floor.
    [Show full text]
  • A Huge Sand Dome Formed by the 1854 Earthquake Tsunami in Suruga Bay, Central Japan
    ISET Journal of Earthquake Technology, Paper No. 462, Vol. 42, No. 4, December 2005, pp. 147-158 A HUGE SAND DOME FORMED BY THE 1854 EARTHQUAKE TSUNAMI IN SURUGA BAY, CENTRAL JAPAN Daisuke Sugawara*, Koji Minoura*, Fumihiko Imamura**, Tomoyuki Takahashi*** and Nobuo Shuto**** *Institute of Geology and Paleontology, Tohoku University, Aobayama, Sendai 980-8578, Japan **Disaster Control Research Center Tohoku University, Aobayama, Sendai 980-8579, Japan ***Department of Civil and Environmental Engineering Akita University, Akita 010-8502, Japan ****Advanced Research Institute for the Science and Humanities Nihon University, Chiyoda-ku 102-8251, Japan ABSTRACT The 1854 Ansei-Tokai earthquake brought massive destruction to Suruga Bay, central Japan. The earthquake triggered a large-scale tsunami, which surged over the Pacific coast of Japan. Waves exceeding 13.2 m in height attacked Iruma, southeastern coast of Suruga Bay, and provoked peculiar types of tsunami sedimentation. On the coast of Iruma, a huge mound of shoreface sand, reaching more than 11.2 m above sea level, appeared after the tsunami run-up. We performed a historical and sedimentological survey to clarify the origin of the mound. Result of a field excavation and submarine investigation suggests that the sand came from the seafloor with a water depth of 20 to 30 m, and historical data illustrates a dramatic change of the landform by the tsunami run-up. Numerical examination of the tsunami implies that the coastal topography played an important role in excitation of the tsunami, and it induced the characteristic tsunami sedimentation. KEYWORDS: Earthquake Tsunami, Tsunami Deposit, Sand Dome, Coastal Topography INTRODUCTION The Pacific coast of central Japan (Tokai region) faces the subduction boundary of the Eurasian and Philippine plates, which forms the Suruga and Nankai troughs (Figures 1(A) and 1(B)).
    [Show full text]
  • Prediction of Tokai Earthquake —
    SCIENCE & TECHNOLOGY TRENDS 3 Gap Between Research and Implementation — Prediction of Tokai Earthquake — SHOZO MAT S U M URA Affiliated Fellow concerned, it without doubt falls into the category 1 Introduction of “implementation of earthquake prediction.” So what is the current situation of “research and In the early morning of August 11, 2009, an implementation of Tokai earthquake prediction?” earthquake with magnitude of 6.5 occurred in As shown in Table 1, diverse organizations are Suruga Bay, shaking such cities as Omaezaki and involved in Tokai earthquake prediction in their Yaizu with an intensity of 6 or lower. Since the respective fields. Among them, the one that is threat of a “Tokai earthquake” had been touted for actually engaged in earthquake prediction is the more than 30 years in Shizuoka Prefecture, many Earthquake Assessment Committee for the Areas people in the prefecture thought that “it (the quake) Under Intensified Measures Against Earthquake was finally here.” Shortly afterward, however, Disaster (hereinafter referred to as EAC), which was they learned that it was not a Tokai earthquake established within the Japan Meteorological Agency after all, but were still concerned that the tremor in 1979. On the other hand, the Coordinating may have been a precursor to a Tokai earthquake. Committee for Earthquake Prediction, which was This is a legitimate concern. However, earthquake established in 1969, is a forum for researchers at researchers have so far been unable to produce any universities and national research institutes.
    [Show full text]