巻号一覧
58 巻 (2012)
- 4 号 p. 131-
- 3 号 p. 107-
- 2 号 p. 61-
- 1 号 p. 1-
58 巻, 2 号
選択された号の論文の4件中1～4を表示しています
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原著論文
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渡部 豪, 田所 敬一, 生田 領野, 杉本 慎吾, 奥田 隆, 永井 悟, 江藤 周平, 久野 正博2012 年 58 巻 2 号 p. 61-76
発行日: 2012年
公開日: 2013/02/26
ジャーナル フリーA number of research institutes have recently conducted seafloor geodetic observations using GPS/Acoustic techniques after offshore earthquakes. A rapid solution is desired from the viewpoints of not only scientific research but also disaster mitigation. Our group has also conducted seafloor geodetic observations using these techniques at the Nankai Trough since 2004. Although we use IGS final orbits for its accuracy, the latency is longer than 13 days. On the other hand, IGS ultra rapid orbits are updated every 6 hours with a delay of 3 hours, which allows us to estimate the deformation due to crustal activity soon after an event. In this study, we compared kinematic GPS solutions obtained using three satellite orbits, namely IGS final, IGS ultra rapid （predicted part）, and broadcast orbits, and assessed their accuracy and effectiveness. We analyzed GPS data for our seafloor geodetic observations conducted in the eastern part of the Kumano Basin on 11 days in 2009 and 2010. GPS data were collected at a rate of 5 Hz with dual-frequency receivers during these observations and analyzed in a post-processing kinematic mode employing a double-difference strategy at each epoch. The average bias and standard deviation of the difference between the solutions obtained using IGS ultra rapid and final orbits were estimated to be 0.3 and 0.5 mm, respectively, with a maximum baseline of 109 km. This result shows that the difference between kinematic GPS solutions obtained using IGS ultra rapid and final orbits is not significant, and the use of IGS ultra rapid orbit is an effective approach to obtain a rapid GPS solution.抄録全体を表示PDF形式でダウンロード (1286K) -
小林 竜也, 太田 雄策, 三浦 哲, 日野 亮太, 藤本 博己, 出町 知嗣, 立花 憲司2012 年 58 巻 2 号 p. 77-87
発行日: 2012年
公開日: 2013/02/26
ジャーナル フリーWe assessed the performance of a permanent displacement detection algorithm, which was developed by the authors at previous study, by using long-term Real Time Kinematic-GPS（RTK-GPS）data processing. False detection of permanent displacement should be avoided for a reliable warning system. We examined the detection rate using RTK-GPS time series with various baselines and different reference sites for a long time period. The false detection rate was ∼0.25% with a 4 sigma confidence level for a single baseline. This false detection rate is inadequate for practical use in a large GPS network consisting of many stations, such as GEONET. We improved the permanent displacement detection algorithm to mitigate the false detection rate. In the improved algorithm, an earthquake occurrence is defined as when the target GPS site and all its neighboring GPS sites detect a displacement. We applied the improved algorithm to an actual data set. With our improved algorithm, the false detection rate decreases to less than 0.002%. When we can use several reference sites for the RTK-GPS data processing and compare results for each reference site, the false detection rate will become almost zero. The improved algorithm is also useful for the detection of small displacements, because it may be possible to lower a threshold value from 4 to 2 sigma while keeping the false detection level to acceptable limit.抄録全体を表示PDF形式でダウンロード (1148K)
奇 書
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小林 裕太, 日置 幸介2012 年 58 巻 2 号 p. 89-93
発行日: 2012年
公開日: 2013/02/26
ジャーナル フリーThe Earth’s spin axis moves by various factors, and mass redistribution associated with seismic faulting is also expected to contribute to this movement. However, there have been no space geodetic observations of coseismic polar motion excitations to date. In this study, we analyze the time series of the excitation functions of the polar motion, and try to detect steps due to the three recent M9 class earthquakes, i.e. the 2004 Sumatra-Andaman, the 2010 Chile （Maule）, and the 2011 Tohoku-Oki earthquakes. For the 2010 Chile earthquake, a significant step was detected but was not consistent with the anticipated direction.抄録全体を表示PDF形式でダウンロード (838K)
報 告
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福﨑 順洋2012 年 58 巻 2 号 p. 95-96
発行日: 2012年
公開日: 2013/02/26
ジャーナル フリーPDF形式でダウンロード (599K)
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