The Distribution Map of Radiation Dose, etc., has been created on the basis of the results of a variety of monitoring activities conducted by the MEXT to give public access to the details of the influence of radioactive substances discharged from TEPCO Fukushima Daiichi Nuclear Power Plant.

Extension Site of Distribution Map of Radiation Dose, etc.

This Extension Site of the Distribution Map for Radiation Dose ( hereafter "this site" ) was prepared in the course of the 2011 Strategic Funds for the Promotion of Science and Technology and entitled "Establishment of the Base for Taking Measures for Environmental Impact of Radioactive Substances-Study of the Distribution of Radioactive Substances"; the 2011 Radioactivity Measurement and Investigation Project commissioned by MEXT entitled "Investigation and Study of the Secondary Distribution of Radioactive Substances due to the Accident at the Fukushima Daiichi Nuclear Power Plant"; and the 2011 Radioactivity Measurement and Investigation Project entitled “Establishment of Technique for Identifying Long-term Impact of Radioactive Substances due to the Accident at the Fukushima Daiichi Nuclear Power Plant based on the Distribution Map of Radiation Dose, etc., the Vehicle-Borne Survey Map, and the results of airborne monitoring projects under the MEXT in order to observe in detail the impacts of radioactive substances discharged from the TEPCO Fukushima Daiichi Nuclear Power Plant.

The Distribution Map of Radiation Dose, etc., is available in either the "Digital Japan Edition" , "PDF Edition" , or "Smartphone Edition." Click the image you want to view in full size.

Read the User Agreement and associated documents prior to use.

Update Information

October 16, 2017
The results of the distribution map of radiation doses (fourteenth vehicle-borne survey) were released in the Web Map Edition and the PDF Edition.
March 17, 2017
The results of the distribution map of radiation doses (thirteenth vehicle-borne survey) were released in the Web Map Edition and the PDF Edition.
February 16, 2017
The results of the airborne monitoring (with dose rate of Nov. 18, 2016) were released in the Web Map and the PDF Edition.
December 5, 2016
The results of the distribution map of radiation doses (twelfth vehicle-borne survey) were released in the Web Map Edition and the PDF Edition.
July 8, 2016
The results of the airborne monitoring (unmanned helicopter), the distribution map of radiation doses (Oct. 2015 soil investigation) were released in the Web Map Edition and the PDF Edition.
March 10, 2016
The results of the distribution map of radiation doses (eleventh vehicle-borne survey) were released in the Digital Japan Edition and the PDF Edition.
February 2, 2016
The results of the airborne monitoring (with dose rate of Nov. 4, 2014) were released in the Digital Japan Edition and the PDF Edition.
November 20, 2015
The results of the distribution map of radiation doses (tenth vehicle-borne survey) were released in the Digital Japan Edition and the PDF Edition.
July 10, 2015
The results of the distribution map of radiation doses (2014 soil investigation) were released in the Digital Japan Edition and the PDF Edition.
March 16, 2015
The results of the distribution map of radiation doses (ninth vehicle-borne survey) were released in the Digital Japan Edition and the PDF Edition.
February 13, 2015
The results of the airborne monitoring (with dose rate of Nov. 7, 2014) were released in the Digital Japan Edition and the PDF Edition.
October 23, 2014
The results of the distribution map of radiation doses (eighth vehicle-borne survey) were released in the Digital Japan Edition and the PDF Edition.
May 19, 2014
The results of the distribution map of radiation doses (seventh vehicle-borne survey) were released in the Digital Japan Edition and the PDF Edition.
March 7, 2014
The results of the airborne monitoring (with dose rate of Nov. 19, 2013) were released in the Digital Japan Edition and the PDF Edition.
December 25, 2013
The results of the airborne monitoring (seventh dose rate) were released in the Digital Japan Edition and the PDF Edition.
December 9, 2013
The results of the distribution map of radiation doses (sixth vehicle-borne survey) were released in the Digital Japan Edition and the PDF Edition.
November 27, 2013
The results of the distribution map of radiation doses (fifth vehicle-borne survey) were released in the Digital Japan Edition and the PDF Edition.
May 13, 2013
The results of the airborne monitoring (with values converted to radiation levels as of Mar. 11, 2013) were released in the Digital Japan Edition and the PDF Edition. The measured value on the airborne monitoring results in the Digital Japan Edition can be viewed from now.
March 12, 2013
Airborne monitoring results in the Digital Japan Edition and the PDF Edition included the data of the 6th and the data outside the 80 km radius area.
February 19, 2013
The results of the airborne monitoring (unmanned helicopter), the distribution map of radiation doses (third soil investigation), and the vehicle-borne survey (fourth) were released in the Digital Japan Edition and the PDF Edition.
December 20, 2012
The measured value of the measurement point on the Distribution Map of Radiation Dose (Vehicle-borne survey) in the Digital Japan Edition can be viewed from now.
November 30, 2012
Airborne monitoring results in the Digital Japan Edition and PDF Edition were added to the Nationwide Edition and the fifth + outside the 80 km radius area, the vehicle-borne survey results were added to the second + third vehicle-borne survey results, and, in addition, the distribution map of radiation dose was added to the second investigation results. The distribution map of radiation dose for the Digital Japan Edition displays the measured values at the measurement points.
October 15, 2012
Distribution Map of Radiation Dose, Digital Japan Edition (Vehicle-borne survey map) was added with the results of the second + the third vehicle-borne surveys (the results of measurement carried out on December 5–28, 2011 and March 13–30, 2012).
September 28, 2012
The PDF Edition was updated. (The past data such as those obtained from airborne monitoring can be also viewed.)
July 11, 2012
The measurement results of the Kinki and Chugoku Regions were published and included in the airborne monitoring results of the Digital Japan Edition.
The locations of primary and junior high schools across the country were included in the Digital Japan Edition.
June 6, 2012
The measurement results of the Shikoku and Kyushu Regions and Okinawa Prefecture were published and included in the airborne monitoring results of the Digital Japan Edition.
April 23, 2012
Snow cover data were included in the airborne monitoring results of the Digital Japan Edition.
March 21, 2012
The measurement results from Dec. 5 to 28 were overlaid on the Distribution Map of Radiation Dose, etc., (Vehicle-Borne Survey Map) of the Digital Japan Edition.
An updated was made to the vehicle-borne survey data of the PDF Edition (survey conducted from Dec. 5 to 28, 2011).
March 12, 2012
The airborne monitoring data from the no-entry zones and planned evacuation zones were published and included in the airborne monitoring results of the Digital Japan Edition.
February 17, 2012
An updated was made to the PDF Edition (with values converted to radiation levels as of Nov. 5, 2011).
February 13, 2012
An updated was made to the Distribution Map of Radiation Dose, etc., of the Smartphone Edition.
January 23, 2012
The results of the 4th MEXT airborne monitoring were published and included in the airborne monitoring results of the Digital Japan Edition.
The Distribution Map of Radiation Dose, etc., covering the entire East Japan was published and included in the PDF Edition.
December 22, 2011
The Distribution Map of Radiation Dose, etc., of the Smartphone Edition was published.
December 21, 2011
The measurement results for Aichi, Aomori, Ishikawa, and Fukui Prefectures were published and included in the airborne monitoring results of the Digital Japan Edition.
The measurement results for Iwate, Shizuoka, Nagano, Yamanashi, Gifu, and Toyama Prefectures were published and included in the airborne monitoring results of the PDF Edition.
The soil concentration maps for tellurium-129 m, silver-110 m, iodine-131, plutonium-238, 239, and 240, and strontium-89 and 90 were overlaid on the Distribution Map of Radiation Dose, etc., of the PDF Edition.
December 1, 2011
The measurement results for Iwate, Shizuoka, Nagano, Yamanashi, Gifu, and Toyama Prefectures were published and included in the airborne monitoring results of the Digital Japan Edition.
The soil concentration maps for tellurium-129 m, silver-110 m, iodine-131, plutonium-238, 239, and 240, and strontium-89 and 90 were added to the Distribution Map of Radiation Dose, etc., of the Digital Japan Edition.
November 8, 2011
The official edition of monitoring results for Tokyo and Kanagawa Prefecture was published and included in the airborne monitoring results.
October 18, 2011
The MEXT Extension Site of the Distribution Map of Radiation Dose, etc., was opened for public access.

About the Establishment of the Extension Site of Distribution Map of Radiation Dose, etc.

1. Background and purpose

This Extension Site of the Distribution Map for Radiation Dose (hereafter “this site”) was prepared in the course of the 2011 Strategic Funds for the Promotion of Science and Technology and entitled “Establishment of the Base for Taking Measures for Environmental Impact of Radioactive Substances—Study of the Distribution of Radioactive Substances”; the 2011 Radioactivity Measurement and Investigation Project commissioned by MEXT entitled “Investigation and Study of the Secondary Distribution of Radioactive Substances due to the Accident at the Fukushima Daiichi Nuclear Power Plant”; and the 2011 Radioactivity Measurement and Investigation Project entitled “Establishment of Technique for Identifying Long-term Impact of Radioactive Substances due to the Accident at the Fukushima Daiichi Nuclear Power Plant based on the Distribution Map of Radiation Dose, etc., the Vehicle-Borne Survey Map, and the results of airborne monitoring projects under the MEXT in order to observe in detail the impacts of radioactive substances discharged from the TEPCO Fukushima Daiichi Nuclear Power Plant.

1. Distribution Map of Radiation Dose, etc.
Air dose rate measurements are taken at one location per 2 × 2 km mesh in the 80 km radius area from TEPCO Fukushima Daiichi Nuclear Power Plant and at one location per 10 × 10 km mesh in the 80 to 100 km radius area and other parts of Fukushima Prefecture outside these areas. Additionally, nuclide analyses are conducted of 5 cm surface soil samples taken from up to five spots per location. The Distribution Map of Radiation Dose, etc., shows the results of the measurements and analyses to enable continuous monitoring of the impact of radioactive substances deposited on the ground surface on resident's health and the environment in future years.
2. Distribution Map of Radiation Dose, etc. (Vehicle-Borne Survey Map)
The Vehicle-Borne Survey Map shows the results of continuous air dose rate monitoring, which are obtained by vehicle-borne surveys* conducted mainly along national and prefectural roads within an approx. 100 km radius area from TEPCO Fukushima Daiichi Nuclear Power Plant to observe in detail the influences of radioactive substances on roadside areas.
*A vehicle-borne survey is a technique in which radiation detectors are installed on vehicles, and gamma rays from radioactive substances deposited on the ground are measured quickly, and in detail, in order to continuously measure air dose rates around roadside areas. In this monitoring survey, the KURAMA system, which was originally developed by Kyoto University, was used with the cooperation of Fukushima Prefecture.
3. Airborne Monitoring Map
The airborne monitoring map is based on the results of airborne monitoring* and the like conducted since April 6, 2011, by the MEXT with cooperation of the US Department of Energy, etc., and shows the air dose rate 1 m above the ground surface and the ground surface deposition densities of radioactive substances at each reading point. This map provides the outline of the influences of radioactive substances deposited on the ground surface.
*Airborne monitoring is a technique in which highly sensitive, large radiation detectors are installed on aircraft, and gamma rays from radioactive substances deposited on the ground are quickly measured over a large area in order to check surface deposition.

The overall map will continue to be updated with additional area maps created based on the originally collected data, and the map based on chronologically newer data will hereafter be published on this site.

Before using this site, carefully read and fully understand the guide to this site and the intent of the information provided in it and agree and consent to the terms and conditions of use.

2. User's Agreement and Terms and Conditions of Use
  • This Agreement provides for the terms and conditions under which the Extension Site of the Distribution Map of Radiation Dose, etc., can be used. In this Agreement, a "User" means a person that uses this site and a "map" refers to cartographic information generated, using GSI Maps geographic information or software (hereafter "geographic information, etc.") via this site, from monitoring-related data measured or published by the MEXT.
  • The maps available on this site use the GSI Maps to provide information on the influences of radioactive substances discharged from TEPCO Fukushima Daiichi Nuclear Power Plant and deposited on the ground surface. The User shall use these maps in accordance with the "Geospatial Information Authority of Japan" Common User's Agreement.
  • The User of this site shall not violate or infringe the property rights and related rights, including personal rights, of the above-mentioned copyright and related rights holders.
  • The User shall be aware that no information available from this site can be used for profit.
  • No map available on this site shall be quoted in any other documents without explicitly referring to the "Extension Site of Distribution Map of Radiation Dose, etc.,/GSI Maps" as the source of the map.
  • The User shall follow the Rules And Manners for Internet Users (Internet Association Japan). The User shall be strictly prohibited from disseminating the types of information that may be deemed as antisocial or illegal in light of the above Rules and Manners.
  • The User shall be solely and entirely responsible for any direct or indirect damage arising from the use of this site; and this site shall not be held responsible or liable in any way for any such damage. The User shall use this site at their own risk and discretion.
  • Upon using this site, the User shall be deemed to have accepted the terms and conditions of this Agreement.
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4. Other remarks
  • Note that the maps available on this site include errors that may occur during the creation of monitoring-related data or cartographic information. These maps are intended for use as reference information.
  • Additionally, monitoring-related data are created using the methods described below. Therefore, measurement values contain some degrees of errors. It should also be noted that various cartographic information may exist and be intermixed on different scale levels (positional accuracy levels).
    1. Distribution Map of Radiation Dose, etc.:The hourly air dose rate (μSv/hour) 1 m above the ground surface at each reading point is determined as follows: individual reading points are identified using commercially available GPS devices; then, at each location with an air dose rate of 30 μSv per hour or less, measurements are taken using a calibrated NaI(Tl) scintillation survey meter; and measurements are taken using a calibrated ion chamber survey meter at each location with an air dose rate exceeding 30 μSv per hour.
      Soil samples taken from up to five spots in each reading point are agitated in suspension for nuclide analysis using a calibrated Ge semiconductor detector. The averaged results of the nuclide analysis provide the basis for the surface deposition densities of iodine-131 and cesium-134 and 137 per unit area (Bq/m2) at each reading point.
    2. Distribution Map of Radiation Dose, etc. (Vehicle-Borne Survey Map):The KURAMA System (Kyoto Univ. RAdiation MApping System) connected to on-vehicle NaI(Tl) scintillation survey meters is used to determine the hourly air dose rate (μSv/hour) 1 m above the road surface (as measured aboard). The values shown on the map as air dose rates measured by the on-vehicle survey meters are determined by factoring in the shielding effect of the construction of the monitoring cars, the installation height of the survey meters, and by multiplication with the correction coefficient for the air dose rates measured inside and outside the cars.
    3. Airborne monitoring map:Using high-sensitivity radiation detectors installed on helicopters, second-by-second measurements are taken of the gamma rays emitted from radioactive substances deposited in circles of a diameter approximately twice the flight altitude (target altitude: 150 to 300 m) centering around ground locations right below the flight trajectories. Then, a dedicated software program is used to determine the hourly air dose rate (μSv/hour) 1 m above the ground surface at each location based on the value of gamma rays measured up in the air and the reading of the survey meter on the ground.
      Meanwhile, the deposition density of radioactive cesium per unit area of ground surface (Bq/m2) is determined, using another dedicated software program, from the relationship between the results of ground surface measurement by a Ge semiconductor detector and the air dose rate 1 m above the ground surface. Note that values for points not flown (i.e., points not present on the flight trajectories) are determined by interpolation from measurement values obtained from points flown.
  • The User's Agreement, etc., (functions, content, terms and conditions, explanations, and all other information) of this site may be subject to change or removal without prior notice. It should also be noted that access to or use of this site may be interrupted from time to time as the result of an update of its content, maintenance and other tasks, or a power failure.
  • If this site is likely to be down due to excessive access requests, priority shall be given to municipal and government officials. For users who are denied access, enlarged versions of maps shall be made available in PDF format (Portable Document Format).