Bulletin of the GSI (Vol.59)
The meridian arc length from the equator to arbitrary latitude is of utmost importance in map projection, particularly in the Gauss-Krüger projection. In Japan, the previously used formula for the meridian arc length was a power series with respect to the first eccentricity squared of the earth ellipsoid, despite the fact that a more concise expansion using the third flattening of the earth ellipsoid has been derived. One of the reasons that this more concise formula has rarely been recognized in Japan is that its derivation is difficult to understand. This paper shows an explicit derivation of a general formula in the form of a power series with respect to the third flattening of the earth ellipsoid. Since the derived formula is suitable for implementation as a computer program, it has been applied to the calculation of coordinate conversion in the Gauss-Krüger projection for trial.
2. Other expressions
3. Derivation of general formula
4. Application to coordinate conversion in the Gauss-Krüger projection
5. Concluding remarks
Takayuki NAKANO, Tetsuro IMAKIIRE, Hideo SAKAI and Keiko MINAMI
To obtain information about the volcanic activity history of the Io To Island in Ogasawara archipelago, the natural remanent magnetization (NRM) of east coast marine deposits and Kama Iwa deposits, where volcanic sedimentary periods have not been clearly determined, were measured. The two deposits, which may have been deposited in similar environments, showed different magnetic orientations. By comparing the NRM results to the geomagnetism change curves for the past 2,000 years in southwest Japan, it was determined that the sedimentary periods were 1,000 years or more apart.
2. Overview of study area
3. Method of study
Great East Japan Earthquake
Tetsuro Imakiire and Tomokazu Kobayashi
This paper presents an overview of crustal deformation caused by the 2011 off the Pacific coast of Tohoku Earthquake, detected by GEONET (GPS Earth Observation Network), the GPS continuous observation system operated by the GSI, and by interferometric SAR (InSAR) analysis using ALOS/PALSAR data. We found that a very wide area of the Japanese Islands, from Hokakido to the Kinki district, was remarkably affected by the crustal deformation caused by the mainshock of the Tohoku Earthquake. We estimated the geometry of the seismogenic fault of the earthquake, as well as the slip model for the plate boundary between the Pacific plate and the North American plate, from the crustal deformation data obtained from GEONET. The fault is estimated to be longer than 400 km, stretching from off Iwate Prefecture in the north to off Ibaraki Prefecture in the south. The largest slip estimate for the plate boundary is more than 56 m in the off-Miyagi region near the Japan Trench. Postseismic crustal deformation is also observed by GEONET, indicating that slow postseismic slip is ongoing along the plate boundary around the main fault zone. Additionally, we detected clear coseismic signals associated with induced inland earthquakes in the Fukushima-Hamadori area from InSAR analysis. The InSAR results show obvious displacement discontinuities, suggesting that rather shallow ruptures occurred. In particular, for the Mj 7.0 event on April 11, the observed displacement boundaries correspond to earthquake surface ruptures that appeared just along the Idosawa and Yunotake faults.
1. Overview of the earthquake
2. Coseismic Crustal Deformation
3. Fault Models
4. Postseismic Crustal Deformation
5. InSAR Analysis
Yohei HIYAMA, Atsushi YAMAGIWA, Toshio KAWAHARA, Masao IWATA,
Yoshihiro FUKUZAKI, Yasushi SHOUJI, Yudai SATO, Toru YUTSUDO, Toshiyuki SASAKI,
Hiromi SHIGEMATSU, Hiromi YAMAO, Takaaki INUKAI, Mitsuo OHTAKI,
Kensuke KOKADO, Shinobu KURIHARA, Isao KIMURA, Takashi TSUTSUMI,
Toshihiro YAHAGI, Yukiko FURUYA, Isao KAGEYAMA, Satoshi KAWAMOTO,
Kazunori YAMAGUCHI, Hiromichi TSUJI and Shoichi MATSUMURA
Large-scale crustal deformation over a wide area of eastern Japan was detected by GEONET, Japan's dense Global Positioning System (GPS) network, following the 2011 off the Pacific coast of Tohoku Earthquake occurred on March 11, 2011. Since it was assumed that coordinates of the control points for public surveys, such as GEONET stations, triangulation stations and leveling bench marks, in a wide area were greatly changed and could hardly maintain consistency between nearby stations, the Geospatial Information Authority of Japan (GSI) stopped providing ‘Survey Results’ of them, which were the coordinates for survey use, and announced it publicly on March 14, 2011.
In order to promote various public restoration programs in the affected area, it was strongly required to revise the Survey Results in an urgent manner. On the other hand, because large postseismic deformation had continued widely after the event, it was concerned that even if the Survey Results were updated immediately, they would become ineffective in a short time. Therefore GSI examined the optimal timing to calculate their new coordinates by predicting the amount of future postseismic movement based on the observation data of GEONET stations. Eventually, the new Survey Results of GEONET stations were published on May 31, 2011 and those of triangulation stations and leveling bench marks on October 31, 2011 respectively.
In this paper we report the revision process of the Survey Results after the 2011 Tohoku Earthquake.
1. Stoppage of Provision of Survey Results of Control Points
2. Required Accuracy and Revision Date for the Survey Results of GEONET Stations
3. Calculation of Survey Results of GEONET Stations
4. Amendment of Coordinate/Elevation of Origins of Japanese Horizontal/Vertical Control Network
5. Revision of Survey Results of Triangulation Stations
6. Revision of Survey Results of Bench Marks
Hiroyuki HASEGAWA, Kanichi SAITO, Hironori TAKAHASHI,
Takao SYUDO, Osamu KAI, Mitsunari HIROTA, Mitsuru SHIBAHARA,
Yuji HATAKEYAMA, Masami NEMOTO, Hiroyuki OHNO, Takayuki ISHIZEKI
As countermeasures for the 2011 off the Pacific coast of Tohoku Earthquake which occurred at 14:46 on March 11, 2011 and the tsunami disaster triggered by this event, the Topographic Department (reorganized as "National Mapping Department" in April of the same year) immediately conducted a series of photograph shooting (color aerial photographs) from the next day (12th) across approximately 6,900 km2 of affected areas from Misawa City in Aomori Prefecture to Soma City in Fukushima Prefecture, and released the aerial photograph images on the Geospatial Information Authority of Japan (GSI) website.
These aerial photograph images were also converted into "orthoimage data" (hereinafter referred to as "orthoimage" (Note that it was created via a simplified method due to the urgency at the time of the disaster)) to overlap with our map, and then the main map information was laid on top of this orthoimage to create an "orthophoto map (orthoimage data + mapping information)" (hereinafter referred to as "orthophoto map").
While these images and maps were released to the public, efforts were made to compile pre and post-disaster photographs of some of the most affected areas and promptly provide these comparison documents to the associated organizations as information that may contribute to disaster response or restoration.
For the recovery/restoration tasks in the affected areas, we also prepared/provided aerial photographic information and the base map for disaster restoration planning to be shared among all organizations associated with public projects.
This report briefly explains about these efforts.
2. Emergency photographing
3. Provision of aerial photograph images and creation of GSI website data
4. Utilizing private aerial photographs
5. Creation of orthoimage and orthophoto map
6. Creating a 1:50,000 scale map for earthquake response
7. Creation of photo mosaics
8. Comparison document of pre and post-disaster aerial photographs
9. Capturing/release of oblique photographs
10. Providing aerial photographs from the emergency photographing
11. Creating a basic map for disaster restoration plan
Hidetoshi NAKAJIMA and Mamoru KOARAI
The massive tsunami from the 2011 off the Pacific Coast of Tohoku Earthquake (hereinafter referred to as the “Tohoku Pacific Coast Earthquake”) that occurred on March 11, 2011, caused devastating damages along the Pacific Coast. The GSI immediately formed an emergency team and started investigating to uncover the situation of tsunami damage.
We emphasized on promptness in the beginning of the survey, created the "Tsunami flood area overview map" with a purpose of improving the accuracy in our best effort over time, and kept on distributing the maps to the municipalities of the affected areas, the national disaster response headquarters etc, while also releasing this information on the GSI website. In addition to calculating the areas of inundation by the municipalities and by land use, an attempt was made to analyze the distance and elevation reached by tsunami in coastal Miyagi Prefecture. Furthermore, elevation was measured precisely by aerial laser survey mainly on areas where ground subsidence occurred due to the earthquake, and high precision elevation data and the digital elevation topographic map have been prepared/provided.
1. Creating an inundation area overview map
2. Announcement of tsunami flood area sizes (approximate numbers)
3. Release of “Tsunami flood area overview map” of the entire area
4. Land use in tsunami flood area
5. Analysis of tsunami travel distance and elevation
6. 1:25,000 Tsunami flood area map
7. Survey of the damages and inundation extent in flood areas
8. Aerial laser survey and creation/provision of digital elevation topographic map