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🏛 | Osaka Metropolis Plan November 11 Referendum for the second time, final edition

The final photo voting campaign.A second referee will be given on the pros and cons of the city plan = 2th, Osaka City Hall

Metropolis plan November 11 Referendum second referee, final edition

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Communist Party-affiliated civil society groups have also called on the audience on the streets, insisting that they should focus on measures against the new Corona and the Nankai Trough giant earthquake.

A referendum on the pros and cons of the "Osaka Metropolis Plan," which abolishes Osaka City and divides and reorganizes it into four special wards, will be held on November 11st, the election day ... → Continue reading

 Osaka Nichi-Nichi Newspaper

Wikipedia related words

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Civic groups

Civic groupsWhat is "Shimindantai"?CitizenUnite to improve their profits, improve their lives, etc.motionOr cause社会To move society by appealing to the upper layers ofSocial movement) Aimed atGroup.Nongovernmental organization,Non profit organizationThere is a big point that both overlap. In the early postwar period, the name "democracy" was also used.

A civic organization has a specific city (Municipalities) May be the group. At this time, with the name of the local government, the townsman group[1], Villagers' organizations[2], Ward groups[3]Sometimes referred to as. The residential areas are sometimes collectively referred to as a resident group. On the other hand, civic groups do not target specific citiesCitizenThere are groups based on groups called layers,memberIn some cases, the place of residence and nationality are not limited.

Civic groups and municipalities

Some local governments may give certain benefits to their civic groups. For example, you have the right to preferentially use the facilities of the local government[4].. In addition, we may hear opinions of civic groups when creating a city.[5].. In such cases, organizations that do not engage in political or religious activities are usually covered.


  1. ^ Example:Nakashibetsu Town Basic Environmental Ordinance・Article 1
  2. ^ Example:Ie Village Regulations and Article 7 on Promotion of Waste Reduction and Proper Treatment
  3. ^ Example:Meguro Residents Center Gymnasium Playground and private use
  4. ^ Example:About Tokorozawa City/Facility Use Civic Group Priority Reservations
  5. ^ Example:Exchange of opinions with Hiratsuka City/Mayor and civic groups

Nankai Trough

Nankai Trough(Some trough,British: Nankai Trough) IsShikokuSouth ofseabedDeep ditch with a depth of 4,000 mtrough<ScaphoidSea basin>).The eastern end is the trough stenosis near Kanesunose, and the western end isKyushu and Palau RidgeIt is the northern end of. South side with Nankai Trough as deformation frontPhilippine Sea PlateIs on the north sideEurasia plate下 にSinkingConvergent type OfPlate boundaryIt is said. At the northern end of the Nankai TroughSuruga BayThe part of the yellow line in the right figure located inside isSuruga TroughAlso called. To the west across the Kyushu-Palau RidgeRyukyu TrenchIs continuous.

Nankai Trough every few decades to hundreds of yearsMega thrustAndEpicenter faultToHuge earthquakeIs believed to be occurring[1].

On the upper board side in parallel with the Nankai Trough subduction zoneSouthwest JapanThe arc extends,AdductAnd ... develop[2].


Plate tectonicsAccording to the interpretation of, the Nankai Trough is a dense ocean plate that has advanced northwest.Philippine Sea PlateIs a low density continental plateEurasia plate(Amur plate) And sinks under it,Subduction zone.

Onshore in the Nankai Trough giant earthquake epicenterGPS observation networkIt was shown that the plate on the land side was moving to the northwest side, and the Eurasian plate on the land side was also dragged along with the Philippine Sea plate due to the sticking between the plates, which was known as the "slip delay velocity distribution".[3],Japan Coast GuardObservations conducted by the United States for about four years from 2011 reiterated that the land-side plate is moving northwest even on the seafloor along the Nankai Trough, and the movement speed varies from sea to sea, but it is the maximum. BecomeEnshu NadaIt is said that the maximum movement is about 6 cm per year (off Lake Hamana) and off the Kii Channel.[4].

The trough axis of the Nankai Trough is in Suruga Bay.Fuji RiverStarting from the vicinity of the river mouthOmaezakiGo south to offshore and then turn southwestCape ShioOki,Muroto CapeThrough the offshoreKyusyuReach offshore. The tip of the western end off the eastern coast of Kyushu isRyukyu Trench(Nansei Islands-OkinawaIt runs north-south on the east side of the road). In addition, the tip of the eastern end near the mouth of the Fuji River is land.Mount Fuji-Mt. Hakone-Tanzawa areaThrough the vicinitySagami TroughHowever, it is not determined which fault zone is the boundary, but rather, there is a view that many fault groups form the mechanical boundary between the plates instead of one connected fault. is there[5].

In the middle of the Showa period after World War IINankai earthquakeTakeo Sawamura, who conducted the research onTonankai earthquakeFocusing on the fact that the epicenter areas of the earthquake extend from east to west parallel to western Japan, we named these epicenter areas "Nankai thrust" because they are thrust faults.[6].. Later, when the plate tectonics theory was generalized, it was found that it was not just a thrust fault but a subduction zone, and since it was less than 6,000 m deep, it came to be called the "Nankai Trough".

Earthquake in Nankai Trough

In various parts of the Nankai Troughmagnitude (M) 8 classesHuge earthquakeOccurs about every 100 to 200 years.

The newest one1944ToKii PeninsulaOff the southeast(I.e.ToTonankai earthquake (M7.9, Mw8.2),1946The epicenter is off the southern coast of the Kii Peninsula.Nankai earthquake (M8.0, Mw8.4) occurred, and all of them caused great damage with more than 2 deaths.However, at this time, it is adjacent to the epicenter of these two earthquakes.Suruga BayNo earthquake occurred in the nearby Nankai Trough (Suruga Trough). In the Suruga Trough, it occurred off the Kii Peninsula with Suruga Bay as the epicenter.1854 OfAnsei Tokai EarthquakeSince then, there have been no earthquakes for more than 150 years. For this reason, a single large earthquake in Suruga Bay where the "plate remained" (Tokai earthquake, The epicenter area is different from the Ansei Tokai earthquake, etc.Assumed Tokai earthquake”) Began to appear around the 1970s, and there was concern that this might occur.Pre slipBased on the theory-based precognition methodLarge-scale Earthquake Countermeasures ActA prediction system based on the above has been established.

On the other hand, just before the Ansei earthquake,Hoei earthquakeAt that time, an earthquake occurred in a wide area from off Shikoku to Suruga Bay at once.Interlocking typeIt became. In this way, it is known that in the Nankai Trough, the mode of occurrence of a huge earthquake is different each time it is repeated. As the government promotes measures against the Tokai earthquake,Tonankai earthquakeとNankai earthquake3 interlockingTokai/Tonankai/Nankai EarthquakeThe movement to assume was suddenly seen in the 2000s, and the assumption was made.However, the Mw 2011 that occurred in 9.0Tohoku-Pacific Ocean EarthquakeHighlighted the possibility of an earthquake of a larger scale than previously expected in the Nankai Trough, and put the M9 class in the expected range.Nankai Trough giant earthquakeIt was decided to revise the assumption.

Furthermore, although not included in these three major earthquakes, the western end of the Nankai Trough (Hinata Nada) OccursHinata Nada EarthquakeThere is something like that. This earthquake is M3 or higher as in the above threeTrench earthquakeThere is currently no record of causing this. However, it is known that earthquakes of around M7.6 occur in a cycle of about 200 years, and earthquakes of M7.0 to 7.2, which are one size smaller, occur in a very short cycle of about 20 to 27 years. Especially1498 Hyuga Nada EarthquakeThen, the possibility that it was linked to (or was part of) the Nankai earthquake,1707 OfHoei earthquakeIt has been pointed out that the Hyuga-nada earthquake may have been linked in addition to the Tokai / Tonankai / Nankai-linked earthquake.

In the field of research on subduction-zone earthquakes, it is the place where information on slip distribution is most abundant.[7]..In addition, as a result of the seismic zone excavation plan described later, traces of thermal displacement due to seismic slip have been found near the trench axis, and there is concern that the generated tsunami will become huge beyond expectations.[8](In the 2011 off the Pacific coast of Tohoku Earthquake, the rupture reached the vicinity of the trench axis).

Mw9.1, maximum in the largest class assumption in the Nankai Trough giant earthquakeSeismic intensity 7(10 municipalities in 153 prefectures), the death toll is estimated to be about 32.

Earthquake zone excavation plan

The "Nankai Trough Earthquake Zone Drilling Program" is being carried out as part of a project by the Integrated Ocean Drilling Program (IODP), which started in October 2003 and is attended by 10 countries. This project is a Japanese deep-sea exploration vessel "ChikyuA deep-sea drilling survey is underway with multiple drillships of special mission drillships provided by Europe, mainly two US drillships. The purpose is to elucidate changes in the global environment, the internal structure of the earth, the biosphere in the crust, etc., and excavation is planned in four stages as a whole. As of 2, stage 4 has been completed and analysis of the collected cores is underway.

Stage 1 (September 2007-February 9)
  • Riserless excavation is carried out in the shallow part (shallower than 1400m) of the huge branch fault and plate boundary fault along the Nankai Trough. At Kumano-nada off the Kii Peninsula, samples of strata at multiple locations were collected at eight locations.
Stage 2 (May-July 2009)
  • The purpose is to elucidate the geological structure and condition by excavating directly above the megathrust earthquake zone (riser and riserless excavation). Observation equipment for monitoring the earthquake preparation process is installed in the excavation hole. In addition, samples of seafloor sediments before subduction into the seismogenic zone were collected together with the plates at three locations.
Stage 3 (September 2010-February 7)
  • Riser drilling was carried out to directly reach the seismogenic zone where huge earthquakes are occurring repeatedly, and seismic material samples were collected directly.
Stage 4
  • We are planning to install a system for long-term observable observations in the drilling holes in the area where a large earthquake occurs. In the future, we are considering cooperation with the earthquake and tsunami observation and monitoring system (DONET).

Main achievements

  • As a result of the 2011 Nankai Trough earthquake zone excavation plan stage 1, the activity traces of the tsunami fault were discovered for the first time from the collected cores.[9]And identified the tsunami fault of the 1944 Tonankai earthquake[10][11]did. In addition, as the activity history of the past Tonankai earthquakes, we found traces from the C004 core, which were previously unknown 1500 ± 34 BC, and about 10600 years ago.
  • On January 2012, 1, research teams such as the Atmosphere and Ocean Research Institute of the University of Tokyo announced that they had discovered a huge fault in the Nankai Trough. It is believed to be a trace of the fault of the Hoei earthquake that occurred in 27.

Observation position

Japan Agency for Marine-Earth Science and TechnologyKumano Nada as a system for constantly observing and monitoring earthquakes and tsunamis operated byDONET(In operation) and from off Tokushima prefecture to Kii Channel off Kochi prefectureDONET2(In operation), and observation data is provided in real time to the National Research Institute for Earth Science and Disaster Prevention and the Japan Meteorological Agency.


  1. ^ Government of Japan Earthquake Research Promotion Headquarters Earthquake Research Committee Earthquake Headquarters> 3. Evaluation Target Areas> Fig. XNUMX Nankai Trough Evaluation Target Areas and Their Classification
  2. ^ "Hamaoka Nuclear Power Station Interplate Earthquake Motion Evaluation (Supplementary Explanatory Material)". Chubu Electric Power (2019). 2021/1/20Browse.
  3. ^ Chihiro Hashimoto, Takeshi Sagiya, Mitsuhiro Matsuura (2009):GPS data inversion (PDF) , 21 Earth Simulator Usage Report Meeting
  4. ^ For the first time, we captured the detailed movement of the seafloor in the hypocenter area of ​​the Nankai Trough giant earthquake-the latest results of seafloor crustal movement observation- Coast Guard August 2015, 8 (PDF)
  5. ^ "Plate boundary fault in the Sagami Trough / Izu collision zone (PDF) , November 2012, 11,Tokyo Metropolitan Earthquake Model Study Group (10th)
  6. ^ Takano Kinnosuke, Takeo Sawamura "Five Great Earthquakes" "Shikoku Mountains" Mainichi Shimbun, 1959
  7. ^ 1946 Nankai Earthquake The effect of the Philippine Sea plate shape on the Nankai Trough giant earthquake estimated from the source process Geoscience magazine Vol.110 (2001) No.4 P498-509
  8. ^ Arito Sakaguchi: Seismic rupture propagation to the trench axis is also in the Nankai Trough Geological Society of Japan 119th Annual Meeting (2012 Osaka) Session ID: S2-O-4 Considering trench-type earthquakes and tsunamis in western Japan, two:10.14863 / geosocabst.2012.0_12
  9. ^ First discovery of tsunami fault activity traces-Results of Nankai Trough earthquake drilling plan by the deep-sea exploration vessel "Chikyu"
  10. ^ Fault slip behavior during an earthquake and its physicochemical aspects revealed by fault drilling research Geoscience Magazine Vol.122 (2013) No.2 Special Issue: Current Status and Prospects of Land Science Drilling in Japan p.323-342, two:10.5026 / jgeography.122.323
  11. ^ Discovery of physical evidence identifying the tsunami fault of the Tonankai earthquake (1944)


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