巻号一覧
59 巻 (2013)
- 4 号 p. 133-
- 3 号 p. 63-
- 2 号 p. 25-
- 1 号 p. 1-
59 巻, 4 号
選択された号の論文の5件中1～5を表示しています
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テクニカルレポート
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―地上通信障害時に地殻変動を実時間で把握するために―山本 淳平, 長田 幸仁, 太田 雄策, 平原 聡, 出町 知嗣, 中山 貴史, 立花 憲司, 佐藤 俊也, 木戸 元之, 藤本 博己, 日 ...2013 年 59 巻 4 号 p. 133-145
発行日: 2013年
公開日: 2015/07/11
ジャーナル フリーThe redundant communication pathway and processing strategy for satellite navigation system such as GPS is extremely important for more reliable quasi real-time crustal deformation monitoring in case of huge interplate earthquake occurrence. We tested real-time kinematic GPS processing (RTK-GPS) via satellite-based mobile phone for redundant communication pathway for address the vulnerabilities of the infrastructure. We succeed to get the stable time series via satellite mobile phone network with almost zero-missing data for short and long baseline RTK-GPS. We also assessed stability, precision and accuracy of StarFireTM global satellites based augmentation system for redundant processing strategy. In order to assess coordinate precision and accuracy, we compared 1Hz StarFire time series and post-processed precise point positioning (PPP) 1Hz time series by GIPSY-OASIS II processing software Ver. 6.1.2 with three different product types (ultrarapid, rapid, and final orbits). We also used different interval clock information (30 and 300 seconds) for the post-processed PPP processing. The standard deviation of real time StarFire time series is less than 30 mm (horizontal components) and 60 mm (vertical component) based on 1 month continuous processing. We also assessed noise spectrum of the estimated time series by StarFire and post-processed GIPSY PPP results. We found that the noise spectrum of StarFire time series is similar pattern with GIPSY-OASIS II processing result based on JPL rapid orbit products with 300 seconds interval clock information. Based on these stability and noise assessment, we suggest that the various communication pathways for RTK-GPS processing and various processing strategy such as global satellites based augmentation system with traditional RTK-GPS processing strategy is important for more reliable quasi real-time crustal deformation monitoring.抄録全体を表示PDF形式でダウンロード (2595K) -
大滝 壽樹, 名和 一成2014 年 59 巻 4 号 p. 147-156
発行日: 2014年
公開日: 2015/07/11
ジャーナル フリーSlow-slip events occur beneath Ishigaki and Iriomote Islands repeatedly once a half year. To detect gravity changes due to the slow-slip events, a superconducting gravimeter has been installed at a VLBI station in Ishigaki Island. Because this station is placed on sedimentary deposits in lowland near a mountain, rainfall around the station may fluctuate nearby underground density distribution. A three-component short-period seismometer has also been installed at the station since March 5, 2012. To explore density variation beneath the station due to rainfall, we analyze differential arrival times of direct P-wave at the station relative to a nearby permanent station for three regional or teleseismic earthquakes. After traveltime correction for the difference of epicentral distances, the net differential travel times are obtained from -0.01 to 0.00 s. These traveltimes only depend on the differences of station height and of seismic velocity structure just below the stations. The mean P-wave velocities in the sediment beneath the temporal station we obtained are between 0.9 and 2.1 km/s. These values are consistent with or close to the water-saturated velocity within a margin of error. These results thus suggest water-saturated sediment beneath the station during the observation period. Temporal variation of the differential times, although it lies within the error bar, seems to correlate to rainfall and soil moisture at the station. Although this method analyzes the discrete data in the time domain, it gives an average sedimentary P-wave velocity. Thus the method gives complementary data to other continuous methods such as soil moisture observation near the surface.抄録全体を表示PDF形式でダウンロード (1085K)
寄書
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中島 悠貴, 日置 幸介2014 年 59 巻 4 号 p. 157-162
発行日: 2014年
公開日: 2015/07/11
ジャーナル フリーMultipath from flat reflecting surfaces causes cyclic changes in quantities such as signal-to-noise ratio （SNR） or L4 （difference between the two L-band phases） of microwave signals from Global Positioning System （GPS） satellites. By analyzing their temporal changes, we can infer heights of GPS antennas from such surfaces, e.g. ground or sea surface. In this study we explore the possibility of measuring the sea surface height （SSH） with GPS stations deployed for crustal deformation measurements. We compared results from the “GPS tide gauges” based on multipath observations and conventional tide gauges during the period from 2012/6/1 to 2012/7/31 at 34 coastal GPS stations, and showed that some of these GPS stations could be used for measuring SSH. For example, SSH measured with Satellite 7 at the Okinawa tide gauge station was accurate to ˜27 cm. This is somewhat lower than those reported in previous works possibly reflecting the longer sampling interval.抄録全体を表示PDF形式でダウンロード (776K) -
橋本 実奈, 日置 幸介2013 年 59 巻 4 号 p. 163-166
発行日: 2013年
公開日: 2015/07/11
ジャーナル フリーGravity fields of the Moon and terrestrial planets are modeled by combining spherical harmonics of various degrees/orders multiplied with the Stokes’ coefficients. These coefficients have been estimated for several celestial bodies including the Earth using tracking data of artificial satellites. The Kaula’s rule-of-thumb predicts that these coefficients are inversely proportional to the square of the degree n of the spherical harmonics. In this study, we confirmed that this is the case for the Moon, the Earth, Mars and Venus. A larger celestial body is hotter inside and has stronger surface gravity, resulting in smaller Stokes’ coefficients. Here we show that such coefficients obey a simple scaling law, i.e. they are inversely proportional to the square of the surface gravity of the body. The Moon has a strong dichotomy, i.e. the nearside has thin crust and flat terrain, whereas the farside has thick crust and rugged terrain. Here we also discuss how far such dichotomy may influence the scaling law.抄録全体を表示PDF形式でダウンロード (752K)
報告
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日置 幸介, 飯沼 卓史, 市川 隆一, 太田 雄策, 大坪 俊通, 鷺谷 威, 島田 誠一, 橋本 学, 福島 登志夫, 福田 洋一, ホ ...2013 年 59 巻 4 号 p. 167-180
発行日: 2013年
公開日: 2015/07/11
ジャーナル フリーPDF形式でダウンロード (6955K)
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