著者

橋本 繭未 日置 幸介

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.64, pp.51-55, 2018 (Released:2019-04-01)

参考文献数

8

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Water vapor molecules from ascending missiles or rockets often cause ionospheric electron depletion, which could be detected as changes in total electron content (TEC) by ground GNSS receivers. Here we present six cases of North Korean missiles/rockets launched in 1998-2017, and compare them with three examples of H2A launches from Japan. We found that the TEC drops are proportional to the background TEC for the same type of rockets, and classified the past cases into three groups using the ratios of TEC drops to the original TEC, i.e. the H2A class, the Taepodong-2 class, and the Taepodon-1 class. Missiles or rockets from North Korea 2009-2016 all belonged to the Taepodong-2 class. In 2017, two inter-continental ballistic missiles (ICBM) were launched from North Korea in July and in November. The first one showed ionospheric electron depletion comparable to the Taepodon-2 class cases, but the second missile much larger TEC drops possibly reflecting a significant technological progress within 2017.

著者

日置 幸介 菅原 守 大関 優 岡崎 郁也

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.56, no.4, pp.125-134, 2010 (Released:2012-03-30)

参考文献数

17

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Two carrier frequencies, L1 and L2, used in Global Positioning System (GPS) can be used to isolate ionospheric total electron contents (TEC) by taking the phase differences between the two carriers (L4). Here we review technical aspects of geophysical applications of TEC measurements. Topics include conversion of standard format raw GPS data files into L4 and TEC, and numerical techniques to isolate disturbance signals with various time scales. We also introduce typical examples of TEC change signatures of variety of geophysical phenomena, e.g. volcanic eruptions, earthquakes, solar flares, ionospheric hole formation by rockets and missiles, solar eclipse, and elusive precursory TEC changes before earthquakes.

著者

森下 遊

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.67, pp.29-39, 2021 (Released:2021-08-20)

参考文献数

19

著者

田島 稔 瀬戸 孝夫

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.15, no.4, pp.150-157, 1970

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国土地理院所属の鹿野山測地観測所における地磁気観測業務の一部が房総西線の直流雹化により支障をきたしたため,岩手県水沢市東方に新たな観測所(水沢測地観測所)を設置することになつた.この際,ごく小数の職員で地磁気連続観測を維持できるように,観測器械の改良を下記の如く行つた. (1)従来の地磁気変化の印画紙記録方式を三成分とも電流帰還型の直視方式にし,記録紙取り換えの手間を省いた. この原理は,H,.D,Z三成分変化計の感度試験用ヘルムホルッコイル枠に,もう一組の変化磁場補償用巻線を加えたものである.光源から出た光はmoving magnetの鏡で反射され受光部に入る.受光部はシリンドリカルレンズを2個はり合せたもので,光路が2つに分けられ,それぞれがCdS感光体に入射する.磁場変化によるスポットの変位は,CdSブリッジに誤差電圧を生じ,増幅されてサーボモーターを駆動し,可変抵抗を調整することにより変化磁場を打ち消す電流を得る.磁場変化に対応した電流は標準抵抗を通し,電圧出力としてERB型の多点記録機に記録される. (2)プロトン磁力計によるF,Hの測定を1分ごとに行い,アナログ記録と同時に,ディジタル記録もとることにした.特に観測所業務で従来多くの時間を要した三成分の毎時平均値を自動的に求めるようにするために,プリンターに,1分ごとの値とともに,毎時間の60回分の積算値も印字させるようにした.しかし三成分のうち偏角についてはプロトン方式よりもD変化計をセンサーに使用する方が簡単なため,直視型D変化計(Suspension magnet type)の出力をA-D変換し,プロトンからのF,Hとともに同じ方式で印字させるようにした.印字の最少単位はF,Hについては0.1γまで可能であり,Dは0.1である.またこれらの印字と並行しテープ穿孔装置も取付けが可能になつている. (3)偏角についてはF,Hと異なり絶対値を獲得しているわけではないので,絶対観測室にてGSI型磁気儀による地磁気ベクトルの方向観測を定期的に行ない,変化計の出力電圧に,基線値に対応する半固定電圧を加えることにより,その時々に対応した値の表示と印字,積算を行なつている. 以上の改良により,すべての装置の記録状態を事務室に隣接した記録計室で直視できるとともに,時間平均値の読み取りは半自動化され,少数の職員による観測業務の維持が可能となつた.

著者

加納 将行

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.68, pp.14-31, 2022 (Released:2023-01-25)

参考文献数

78

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Dense geodetic observation networks have contributed to observing a wide variety of fault slips with different time scales including coseismic slips, slow slip events, afterslips, and stable slips. These slip behaviors may be a result of heterogeneous physical properties, especially frictional properties, along the plate interface. I have conducted a series of studies for understanding and predicting such various fault slip behavior based on geodetic data analysis, numerical simulation, and data assimilation. This article briefly summarizes my works on data assimilation of estimating frictional properties and predicting fault slip in the case of the 2003 Tokachi-oki afterslip, and geodetic data analysis on slow slip events concerning anticipated earthquakes in southwest Japan.

著者

水藤 尚

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.62, no.3, pp.109-120, 2017-03-25 (Released:2017-04-30)

参考文献数

43

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We evaluate how large interplate fault slip around Japan can be detected by the GNSS Earth observation network system (GEONET), based on the dislocation theory. The detectability is calculated in term of two characteristic parameters; threshold and number of station. Evaluation of detectability of interplate fault slip has indicated that GEONET have the monitoring capability at least Mw6.5 or more on the Pacific plate and Mw6.0 or more on the Philippine Sea plate, when the threshold and number of station are 7 mm in horizontal, 14 mm in vertical and 3 sites or more, respectively. It should be noted that the detectability depends on the assumed parameters, such as threshold, number of station and fault parameters. The detectability gets worse when the threshold or number of station is larger. The detectability greatly depends on the threshold than the number of station. The detectability also depends on the assumed fault parameters, and its difference causes magnitude gain or loss up to Mw0.5 at maximum. We consider that these results are a first step for understanding the detectability of the interplate fault slip on the Pacific plate and the Philippine Sea plate based on GEONET.

著者

村上 真幸

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.45, no.3, pp.229-239, 1999-09-25 (Released:2011-07-05)

参考文献数

23

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The Geographical Survey Institute (GSI) is preparing the establishment of Japan's new geodetic datum, Japanese Geodetic Datum 2000 (JGD2000), and its realization, Geodetic Coordinates 2000, based on a geocentric system. This review paper focuses on historical background regarding the establishment of geodetic datums and the present situation of Japan'sdatum to help readers understand the idea of, and background for the move to the new geodetic datum.

著者

上西 勝也

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.55, no.1, pp.95-102, 2009 (Released:2012-01-31)

参考文献数

22

被引用文献数

1

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Full-dressed geodetic survey in Japan was carried out after late 19th century. A few monuments of the survey facilities in the fields are still remained. Some survey markers, observation tables, memorials were placed by former organizations, Ministry of Interior, Earthquake Investigation Committee, and Geodetic Committee of Japan. This paper shows historical review of old geodetic survey activities and their monuments in the fields. The author would expect these historical monuments to be conserved.

著者

今給黎 哲郎 大瀧 茂 熊木 洋太 畑中 雄樹 松村 正一 村上 亮 山際 敦史

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.50, no.2, pp.53-65, 2004-06-25 (Released:2010-09-07)

参考文献数

48

被引用文献数

2

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GEONET (GPS Earth Observation Network System), which is a nationwide GPS array and data analysis system of the Geographical Survey Institute, started in 1994. Since then, it has been expanded and improved to monitor crustal deformation of Japanese islands quickly and accurately. Today, it is the densest GPS observation network in the world with 1, 200 GPSbased control stations and some other stations. GEONET has contributed its continuous data to various fields of earth science. In seismo tectonics study, it provided the features of coseismic crustal deformation as well as the steady state crustal deformations by plate motion. Five interplate slow slip events were also found by GEONET and has been playing important role to the recent plate coupling studies. In volcanological study, it provided the sequence of magma activity utilized for the estimation of eruption. GEONET also provided a new measure to detect ionospheric and meteorological signals and have been contributing to atmospheric science. The observed 1 Hz data of almost all stations are now provided to commercial users for positioning services in real time. GEONET is becoming a kind of infrastructure of the locationbased information society. The major present research subjects are improvement of the detectability, development of real-time analysis of crustal deformation, etc. It is also important for the future use of GEONET to maintain observation circumstances properly and to be adapted to the GPS modernization and new GNSSs.

著者

Masanao Abe Masatsugu Ooe

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.47, no.1, pp.514-520, 2001-03-25 (Released:2010-09-07)

参考文献数

6

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Tidal evolution of the earth-moon system was evaluated by estimating the change of dynamic responses of ocean and solid earth to the lunar and solar tidal force during the geological time. The effect of tide on the moon due to the earth was included in the evaluation. We obtained time variations of the orbital elements of the moon, the LOD (length of day) and obliquity of the spin axis of the earth. Our previous study suggested that the variation of LOD up to 600 million years before present estimated by paleontological studies is explained by temporal variation of the ocean continent distribution (Abe et al., 1997). In this study, we paid attention to discriminate how the continental distribution before 500 million years ago affects evaluation of the evolution process, using the continental distribution at 540 million years ago and 700-750 million years ago referred from Maruyama et al. (1997). After making investigations replacing the continental models used in the previous paper, it was suggested the results did not suffer so serious from ambiguity of continent models before about 1.5 billion yeas ago. This point leads us to understand that the small effect of the variation of continent models around these eras comes from the fact that the tidal frequency was remarkably far from the eigen-frequency of tidal response of the oceans. This also suggests that the earlier stage of the earth-moon system, than about 1.5 billion years ago, was possibly governed by mostly small and constant tidal response of the oceans and the comparable or larger effect of tides of the solid earth. Assuming the surface of the earth covered by whole ocean before 2.5 billion years ago, the time when earth-moon distance was very short is around 4.5 billion years ago and we can make almost clear the whole history of the earth-moon dynamical system due to tide after the moon was generated.

著者

駒澤 正夫

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.41, no.1, pp.17-45, 1995-03-25 (Released:2011-07-05)

参考文献数

48

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阿蘇火山およびその周辺域について重力データの収集と補間測定を行ない,阿蘇火山の微細なブーゲー異常と密度構造を明らかにした.カルデラ構造を不鮮明にしている表層の火砕物や堆積物の効果をはぎ取るために,上方接続残差分散比較法(CVUR法)を提案する.その方法を適用した結果,阿蘇火山の表層密度は2.2~2.39/cm 3と妥当な値を得た. 測点数が増したことにより,阿蘇カルデラが漏斗型(倒立円錐状)の構造をもった単純な「低重力タイプのカルデラ」ではなく,5つの低重力異常域が南北に並んでいることが判明した.また,個々の低重力異常域はカルデラ壁の内側で急勾配をもつが,低重力異常の中心部では底が平坦であることもわかった. カルデラ内の湖性堆積物や火砕堆積層の層厚の見積もりのモデルとして,表層上面と基盤面(表層下面)にそれぞれ面的に密度変化を与え,その両面を2次式で接続させるものを想定し,その構造に基づく3次元解析法を新たに提案する.その結果,重力基盤構造は,カルデラ内で急傾斜で500mほど陥没し,カルデラ内の5つの低重力異常域に対応してさらに200~400mほどの陥没があり,底は平坦である.重力基盤構造からは,阿蘇カルデラが濁川カルデラのように巨大な爆裂による「漏斗型カルデラ」とは読み取れず,大規模な陥没を伴ったValles-typeといわれる「ピストン・シリンダー型」に類似する構造が配列することがわかった.また,中央火口丘からその北側には,周辺域より0.1g/cm 3ほど密度の小さい基盤が推定され,深部との連続性とともに,陥没域には,強溶結した溶結凝灰岩や火砕流の存在が考えられる.

著者

宮地 政司

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.20, no.1-2, pp.100-104, 1974-08-25 (Released:2010-09-07)

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すでに現役を退いた私が,そうそうたる現役会員のまえで特別講演などをすることは,まことにおこがましい限りですが,齢に免じてお許し願います.さて講演の内容ですが,標題の「時」は時間・時刻のことで,私の現役時代の主要な仕事でした.「測地」の方は測地学・測地測量の両方を包含した意味であります.この両者の関係について,半世紀まえに行った経度観測の話から,最近の測地衛星や月レーザ観測のアピールまであれこれと話を進めたいと考えております.ご参考にでもなれば幸です.

著者

長沢 工

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.44, no.3, pp.189, 1998-09-25 (Released:2010-09-07)

著者

中川 一郎

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.21, no.4, pp.206-220, 1976-03-25 (Released:2011-03-01)

著者

福田 洋一 服部 晃久 奥野 淳一 青山 雄一 土井 浩一郎

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.68, pp.1-13, 2022 (Released:2022-05-18)

参考文献数

29

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National Institute of Polar Research (NIPR) has been conducting absolute gravity measurements not only at Japanese Antarctic research station, Syowa since early 1990s, but also other foreign research stations in Antarctica recently. To validate the absolute gravimeter employed, test measurements were conducted at the gravity point located at the machine shop in NIPR usually before and after the measurements in Antarctica. The observed gravity values at the point, however, often varied exceed the expected instrumental errors. To explain the causes of the large gravity variations, we compared the observed gravity values with the precipitations at three AMeDAS(Automated Meteorological Data Acquisition System)stations, groundwater levels at a Tokyo Metropolitan Government observatory, and the height data at four GEONET (GNSS Earth Observation Network System)stations. The result of the comparisons showed that 1) the seasonal or shorter gravity variations were mainly caused by the precipitations and the resultant soil moisture and/or shallow groundwater changes, and 2) the secular or longer period gravity variations were explained by the uplift after the 2011 Tohoku-oki earthquake and the long-term variations of the groundwater level at deeper depths. After removing these effects, the standard deviation of the gravity residuals was less than 3 µGal (1 µGal=10−8 m/s2).

著者

. 奥山 哲 竹本 修三

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.49, no.1, pp.73-82, 2003

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重力データの解釈にはよく知られているようにインバージョンにおける解の非唯一性の問題がっきまとうため,この種の処理にはアプリオリな付加的情報が必要となる.先験的な地質学,幾何学の知識及びさらにいくつかの付加的な情報,例えば構造断面や等高線の様相などは,モデリングをより一層扱いやすいものにすることができる.われわれは,断層の走向,長さ,高さ及び深さ方向の拡がりのサブセットからなるパラメータを用いて日本の中部山岳地帯の糸魚川一静岡構造線(ISTL)に沿う断層を横切る重力インバージョン解析を行った.その結果,重力データに基づく2次元のモデリングは,断層を横切るもっともらしい下部構造を描くために行われた反射法及び屈折法探査などの以前の研究と整合する.すなわち,験震学的には構造線の南西あるいは西に厚い堆積盆地が存在することが示唆されているが,同様の結果がわれわれの解析からも確かめられた.つまり,南西あるいは西方の3~3.5kmの深さに堆積層があり,その構造は西に向かうほど狭くなっている.

著者

飯島 重孝 岡崎 清市

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.8, no.3-4, pp.126-134, 1963-03-31 (Released:2011-07-05)

参考文献数

17

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Variations in the rate of rotation of the Earth are determined from the comparison of the mean UT1 against an atomic time scale for the period of 7 years from 1956 to 1962. The mean UT1 is that obtained from the weighted mean of the data of eleven observatories which have kept good time observations for the period from 1955.5 to 61.5, and for-the remainning period from 1961.5 to 62.9 only the data of the Tokyo UT1 is used instead Corrections for the longitude variation which are used to obtain the true UT1 are calcu-lated from the instantaneous pole's coordinates of the Earth determined by the same authors solely from the time observation data. While, the atomic time scale is principally based on cesium frequency standards at the N. P. L. (England) and the N. R. L. (U. S. A.). As a result of this comparison correction for the seasonal variation in the rate of rotation of the Earth is separated as follows, where t is the fractions of year. As for the residual variations the general aspect of the clock-face of the “Earth Clock” may be represented by five pieces of straight lines with different inclinations for the fractional periods, 1956.057.2 (-115 × 10-10), 1957.2-58.5 (-165 × 10-10), 1958.5-60.4 (-150 × 10-10), 1960.4-62.3 (-130 × 10-10) and 1962.3- (-155 × 10-10 ?). In these residual variations, moreover, the existence of a periodic term of some 5.5 years is plausible, although it is not yet definite.

著者

村上 真幸 仙石 新

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.53, no.1, pp.1-12, 2007-03-25 (Released:2011-03-01)

参考文献数

21

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This paper describes the background of, and the necessity for the transition of the Japanese national geodetic datum from Tokyo Datum to the geocentric geodetic datum (or world geodetic system). Historically, the shape and scale of an earth ellipsoid have become accurately determined with the development of artificial satellites and laser ranging technique, and the position of an earth ellipsoid relative to the earth has been accurately determined by space geodetic techniques such as VLBI, SLR and GPS. As a result, at the end of the twentieth cen tury, geocentric geodetic datums, ITRF and WGS 84, were established and many international organizations recommend adopting ITRF or WGS 84 as the standard datum. Recent prevail ing use of GPS in surveying and navigation reveals the difference between traditional datum and geocentric datum to users of maps and charts. To leave the difference as it is would make confusion and could cause an accident if one makes positioning by GPS based on geocentric datum while using maps/charts based on traditional datum. Transition of datum from traditional one to geocentric one appears inevitable. Two governmental organizations, the Geographical Survey Institute (GSI) and the Hydrographic and Oceanographic Department of Japan Coast Guard (JHOD) made much effort to realize a new Japanese geodetic datum basedon a geocentric datum and develop maps and charts (both paper-based and digital ones) referenced to the new datum. They also collaborated to have relevant laws (Survey Act and Law for Hydrographic Activities) to be amended which regulate the geodetic datum to be used in Japan. The amended laws became effective on April 1, 2002, and the datum change was propagated among Japan without serious troubles owing to extensive preparations.

著者

飛田 幹男 辻 宏道 高橋 保博 川原 敏雄

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.49, no.3, pp.181-192, 2003-09-25 (Released:2010-09-07)

参考文献数

9

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Correction vectors from coordinates in datum sheet to coordinates surveyed by static GPS at 57 Japanese islands in Tokyo Datum are calculated and compiled. The magnitude of the corrections of Iwo-jima, Daito-jima, Tarama-jima, Ishigaki-jima, and Yonaguni-jima islands exceeds 200 m, because the coordinates in datum sheet in Tokyo Datum were determined by astronomical survey of several tens of years ago. The correction vectors represent internal consistency in Tokyo Datum and can be used for corrections of island maps in Tokyo Datum, e.g., maps in car navigation systems.

著者

飛田 幹男 宗包 浩志 海津 優 松坂 茂 黒石 裕樹 眞暗 良光 加藤 敏

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.50, no.1, pp.27-37, 2004-03-25 (Released:2010-09-07)

参考文献数

14

被引用文献数

1

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The source of seasonal groundwater level variation, which is closely related to the variation of GPS vertical component, was investigated. We found that groundwater pumping for paddy field irrigation from May to August caused drawdown of groundwater level by 7m and this caused temporal subsidence by about 2 cm in Geographical Survey Institute, Tsukuba. Elastic deformation of gravel layers explains the process that groundwater level variation causes variation of ground height, because the height recovers completely and there is no delay between the two variations. The scale error of GEONET due to the seasonal height variation of the fixed GPS station at GSI is estimated to be±0.3 ppb.