Editing Tokyo (section)

=== Natural disasters ===

==== Earthquakes ====
[[File:Yurakucho after Great Kanto earthquake.JPG|right|thumb|The [[1923 Great Kantō earthquake|Great Kanto Earthquake]] in 1923 killed more than 100,000 citizens in Tokyo.]]
Tokyo is near the [[Boso triple junction|boundary of three plates]], making it an extremely active region for smaller quakes and [[Slow earthquake|slippage]] which frequently affect the urban area with swaying as if in a boat, although epicenters within mainland Tokyo (excluding Tokyo's {{cvt|2,000.|km}}–long island jurisdiction) are quite rare. It is not uncommon in the metro area to have hundreds of these minor quakes (magnitudes 4–6) that can be felt in a single year, something residents merely brush off but can be a source of anxiety not only for foreign visitors but for Japanese from elsewhere as well. They rarely cause much damage (sometimes a few injuries) as they are either too small or far away as quakes tend to dance around the region. Particularly active are offshore regions and to a lesser extent [[Chiba Prefecture|Chiba]] and [[Ibaraki Prefecture|Ibaraki]].<ref>{{cite journal |last=Matsu'ura |first=Ritsuko S. |date=January 28, 2017 |title=A short history of Japanese historical seismology: past and the present |journal=Geoscience Letters |volume=4 |issue=1 |page=3 |bibcode=2017GSL.....4....3M |doi=10.1186/s40562-017-0069-4 |via=BioMed Central |doi-access=free}}</ref>

Tokyo has been hit by powerful [[megathrust]] earthquakes in 1703, 1782, 1812, 1855, 1923, and much more indirectly (with some [[soil liquefaction|liquefaction]] in landfill zones) in [[2011 Tōhoku earthquake and tsunami|2011]];<ref>{{cite journal |last1=Grunewald |first1=Elliot D. |last2=Stein |first2=Ross S. |year=2006 |title=A New 1649–1884 Catalog of Destructive Earthquakes near Tokyo and Implications for the Long-term Seismic Process |journal=Journal of Geophysical Research: Solid Earth |volume=111 |issue=B12 |pages=B12306 |bibcode=2006JGRB..11112306G |doi=10.1029/2005JB004059 |doi-access=free}}</ref><ref>{{cite web |title=A new probabilistic seismic hazard assessment for greater Tokyo |url=http://walrus.wr.usgs.gov/reports/reprints/Stein_PRSLA_364.pdf |url-status=live |archive-url=https://web.archive.org/web/20071025030342/http://walrus.wr.usgs.gov/reports/reprints/Stein_PRSLA_364.pdf |archive-date=October 25, 2007 |access-date=October 14, 2007 |website=U.S. Geological Survey}}</ref> the frequency of direct and large quakes is a relative rarity. The [[1923 Great Kantō earthquake|1923 earthquake]], with an estimated magnitude of 7.9, killed more than 100,000 people, the last time the urban area was directly hit.<ref>{{Cite news |title=関東大震災から100年「防災の日」に各地で慰霊や訓練 |trans-title=Memorials and drills held across Japan on Disaster Prevention Day, 100 years after the Great Kanto Earthquake |url=https://www3.nhk.or.jp/news/html/20230901/k10014180721000.html |access-date=28 June 2024 |website=NHK |date=1 September 2023 |language=ja |archive-date=June 29, 2024 |archive-url=https://web.archive.org/web/20240629041006/https://www3.nhk.or.jp/news/html/20230901/k10014180721000.html |url-status=live }}</ref><ref>{{cite news |title=Tokyo braces for another 'big one' on 100th anniversary of deadly quake |language=en |url=https://www.theguardian.com/world/2023/sep/01/tokyo-braces-for-another-big-one-on-100th-anniversary-of-deadly-quake |access-date=28 June 2024 |work=The Guardian |date=31 August 2023 |archive-date=July 24, 2024 |archive-url=https://web.archive.org/web/20240724234631/https://www.theguardian.com/world/2023/sep/01/tokyo-braces-for-another-big-one-on-100th-anniversary-of-deadly-quake |url-status=live }}</ref><ref>{{cite news |title=Japan marks 100 years since the devastating Great Kanto Quake, with disaster drills nationwide |language=en |url=https://apnews.com/article/japan-tokyo-quake-centennial-disaster-drills-64e84452dacfec3b7b6024b107b1a77d |access-date=28 June 2024 |work=AP |date=1 September 2023 |archive-date=June 29, 2024 |archive-url=https://web.archive.org/web/20240629041005/https://apnews.com/article/japan-tokyo-quake-centennial-disaster-drills-64e84452dacfec3b7b6024b107b1a77d |url-status=live }}</ref>

==== Volcanic eruptions ====
[[File:宝永大噴火を描いた絵図「夜ルの景気」(静岡県沼津市土屋博氏所蔵).jpg|thumb|[[Mount Fuji]] has posed the primary volcanic threat to Tokyo's citizens for centuries.]]
[[Mount Fuji]] is about {{cvt|100|km|mi}} southwest of Tokyo. There is a low risk of eruption. The last recorded was the [[Hōei eruption of Mount Fuji|Hōei eruption]] which started on December 16, 1707, and ended about January 1, 1708 (16 days).<ref name="ShizuokaUni">{{cite web |author=Masato Oyama |date=March 2007 |script-title=ja:宝永四年（1707）噴火 (1707 Eruption) |url=http://sk01.ed.shizuoka.ac.jp/koyama/public_html/Fuji/fujid/1707.html |url-status=dead |archive-url=https://web.archive.org/web/20170812141355/http://sk01.ed.shizuoka.ac.jp/koyama/public_html/Fuji/fujid/1707.html |archive-date=August 12, 2017 |access-date=September 25, 2008 |publisher=Shizuoka University |language=ja |script-work=ja:富士山歴史噴火総解説 (Database of eruptions and other activities of Fuji Volcano, Japan, based on historical records since AD 781)}}</ref> During the Hōei eruption, the ash amount was 4&nbsp;cm in southern Tokyo (bay area) and 2&nbsp;cm to 0.5&nbsp;cm in central Tokyo.<ref name="Hoei-eruption-map">https://commons.wikimedia.org/wiki/File:Volcanic-ash-downfall_map_of_Mt.Fuji_Hoei-eruption01.jpg {{Webarchive|url=https://web.archive.org/web/20210818054657/https://commons.wikimedia.org/wiki/File:Volcanic-ash-downfall_map_of_Mt.Fuji_Hoei-eruption01.jpg |date=August 18, 2021 }} Ashfall distribution map for examining disaster prevention measures (Mt. Fuji Hoei eruption)</ref> [[Kanagawa]] had 16&nbsp;cm to 8&nbsp;cm ash and [[Saitama Prefecture|Saitama]] 0.5 to 0&nbsp;cm.<ref name="Hoei-eruption-map" /> If the wind blows north-east it could send [[volcanic ash]] to Tokyo metropolis.<ref name="fuji-eruption">{{cite web |title=Mt Fuji eruption could cripple Tokyo | date=March 31, 2020 |url=https://www.youtube.com/watch?v=JJjugxAdPYQ |archive-url=https://web.archive.org/web/20201108023355/https://www.youtube.com/watch?v=JJjugxAdPYQ |archive-date=November 8, 2020 |publisher=Nippon TV News 24 Japan |via=YouTube}}</ref> According to the government, less than a millimeter of the volcanic ash from a Mount Fuji eruption could cause power grid problems such as blackouts and stop trains in the Tokyo metropolitan area.<ref name="fuji-eruption" /> A mixture of ash with rain could stick to cellphone antennas and power lines and cause temporary power outages.<ref name="fuji-eruption" /> The affected areas would need to be evacuated.<ref name="fuji-eruption" />

==== Floods ====
[[File:Tokyoflood.jpg|left|thumb|The Great Flood of August 1910, [[Taitō|Taito]]]]
Tokyo is located on the [[Kantō Plain]] with five river systems and dozens of rivers that expand during each season.<ref name="flood-protection">{{cite web |date=November 29, 2018 |title=The underground cathedral protecting Tokyo from floods |url=https://www.bbc.com/future/article/20181129-the-underground-cathedral-protecting-tokyo-from-floods |archive-url=https://web.archive.org/web/20201108092638/https://www.bbc.com/future/article/20181129-the-underground-cathedral-protecting-tokyo-from-floods |archive-date=November 8, 2020 |website=BBC}}</ref> Important rivers are [[Edo River|Edogawa]], [[Naka River (Saitama Tokyo)|Nakagawa]], [[Arakawa River (Kantō)|Arakawa]], [[Kanda River|Kandagawa]], [[Meguro River|Megurogawa]] and [[Tama River|Tamagawa]].<ref name="flood-tokyo">{{cite web |date=February 28, 2020 |title=Floods in Tokyo and Safety Tips and Preparation |url=https://www.realestate-tokyo.com/living-in-tokyo/emergency-disaster/flood-in-tokyo-japan/ |archive-url=https://web.archive.org/web/20200814012652/https://www.realestate-tokyo.com/living-in-tokyo/emergency-disaster/flood-in-tokyo-japan/ |archive-date=August 14, 2020 |website=Plaza Homes}}</ref> In 1947, [[Typhoon Kathleen]] struck Tokyo, destroying 31,000 homes and killing 1,100 people.<ref name="flood-protection" /> In 1958, [[Typhoon Ida (1958)|Typhoon Ida]] dropped {{convert|400|mm|in|abbr=on}} of rain in a single week, causing streets to flood.<ref name="flood-protection" /> In the 1950s and 1960s, the [[Government of Japan|government]] invested 6–7% of the national budget on disaster and risk reduction.<ref name="flood-protection" /> A huge system of dams, levees, and tunnels was constructed.<ref name="flood-protection" /> The purpose is to manage heavy rain, [[typhoon|typhonic]] rain, and river floods.<ref name="flood-protection" />[[File:Geofront_Temple^_首都圏外郭放水路_-_panoramio.jpg|thumb|The [[Metropolitan Area Outer Underground Discharge Channel|MAOUDC]] is the world's largest underground floodwater diversion facility.]]Tokyo has currently the world's largest underground floodwater diversion facility called the [[Metropolitan Area Outer Underground Discharge Channel]] (MAOUDC).<ref name="maoudc">{{cite web |title=Metropolitan Area Outer Underground Discharge Channel |url=http://www.afar.com/places/metropolitan-area-outer-underground-discharge-channel-kasukabe |archive-url=https://web.archive.org/web/20180914132022/https://www.afar.com/places/metropolitan-area-outer-underground-discharge-channel-kasukabe |archive-date=September 14, 2018 |access-date=January 10, 2015}}</ref><ref name="flood-protection" /> It took 13 years to build and was completed in 2006. The MAOUDC is a {{convert|6.3|km|mi|abbr=on}} long system of tunnels, {{convert|22|m|ft|sp=us}} underground, with {{convert|70|m|ft|sp=us|adj=on}} tall cylindrical tanks, each tank being large enough to fit a space shuttle or the Statue of Liberty.<ref name="flood-protection" /> During floods, excess water is collected from rivers and drained to the [[Edo River]].<ref name="flood-tokyo" /> Low-lying areas of [[Kōtō]], [[Edogawa, Tokyo|Edogawa]], [[Sumida, Tokyo|Sumida]], [[Katsushika]], [[Taitō]] and [[Arakawa, Tokyo|Arakawa]] near the [[Arakawa River (Kanto)|Arakawa River]] are most at risk of flooding.<ref name="flood-tokyo" />