地震 第2輯 (1)
岩野 祥子 (5)
福田 洋一 (4)
井上 直人 (1)
伊藤 陽之 (1)
北田 奈緒子 (1)
2004 年 (2)
2000 年 (1)
2001 年 (1)
2005 年 (1)
2018 年 (1)
小林 佑輝, 岩野 祥子, 福田 洋一
2004年 50 巻 1 号 17-26
In order to improve the accuracy of the estimated oceanic tidal loading effects at Syowa Station, and some of bared areas along Lutzow-holm Bay, Antarctica, we made a detailed coastline data set. The coastline data, grid size of which corresponds to so-called 4 th mesh (1.5"×2.25"grids) of the GOTIC2 software, are read from 1/25, 000 scale maps around Syowa Station over a 1.5 degrees by 1.5 degrees area. Using this data set and the NA0 .99b ocean tide model, we calculated oceanic tidal effects for gravity (GV), radial displacement (RD), and horizontal displacement (HD) at Syowa Station and nearby areas . At Syowa Station, obtained amplitudes and phases of M2, S2, 01, and K1 waves for GV are (2.302, iGa1, 351.38 deg.), (1.585μGal, 1.39 deg.), (2.504μGal, 349.14 deg.) and (1.953μGal, 352.33 deg.), respectively. The amplitude of RD and HD at Syowa Station are 56 mm and 14 mm, respectively, while the rela tive amplitudes of RD and HD between Syowa Station and Skalen, one of the GPS observation sites at the bared areas, are 8 mm and 1.3 mm, respectively. Newly estimated gravity effects will allow us to get accurate tidal admittance for the superconducting gravimeter observa tions at Syowa Station. The result also shows that the oceanic tidal effects on VLBI and/or GPS observations are not negligible, if the observation points are near the sea .
井上 直人, 田中 靖之, 伊藤 陽之, 岩野 祥子, 北田 奈緒子, 福田 洋一, 竹村 恵二
2004年 57 巻 1 号 45-54
The Horikawa-Oguraike and Kuzebashi seismic reflection and refraction profiles were obtained in the Kyoto Basin from 1998 to 1999. The gravity measurements were conducted at 50-300m station intervals along the seismic profiles in order to estimate the density of sediments in the basin. The N-S and E-W gravity profiles correspond to the Horikawa-Oguraike and the Kuzebashi seismic profiles, respectively. The Kyoto Basin was composed of basement rocks covered by unconsolidated sedimentary layers. The top surface of the basement of 2D two-layers models were constructed with the constraints of seismic profiles. The inferred density contrast between the basement and the overlaying sediments in the N-S two-layer model was 0.3g/cm
and the difference between observed and calculated gravity anomalies was within 1.5m gal. The results of the density loggings and the distribution of the seismic velocities along the Horikawa-Oguraike seismic section indicate the density variation. The multi-layered N-S model was constructed based on the seismic profile and the borehole data. On the other hand, the density contrast between the sedimentary cover and the basement in the E-W two-layer model was 0.7g/cm
and the difference between observed and calculated gravity anomalies was within 1mgal. The regional gravity trend inferred from this study tilts toward the northeast in the Kyoto Basin.
岩野 祥子, 福田 洋一
2000年 46 巻 2 号 149-152
In order to get precise Bouguer anomalies, terrain correction is very important. Especially for so called micro gravity surveys, which have been widely applied for various purposes recently, the accuracy of the terrain correction seriously de pends on the grid size of Digital Elevation Model (DEM). We thus studied the relation between the accuracy of the terrain correction and the DEM employed for the calculation with a special attention of its spatial resolution. Practically, the 50 mintervals DEM (50 mDEM) published by the Geo graphical Survey Institute have been widely used for gravity terrain correction in Japan . We there fore decided to estimate the accuracy of terrain correction using 50 mDEM as one of the standard cases. We made 10 mDEM from 1/2, 500 city planning maps and compared the two Bouguer gravity anomalies obtained by using the 50 mDEM and the10 mDEM, respectively. The result shows that about 0.2 mgal or a better terrain correction can be obtained only by using the 50 mDEM in topographically flat areas. However, we need more detailed terrain data in topographically steep mountain areas, or even in flat areas to achieve accurate terrain correction of better than 0.1 mgal.
平田 雅昭, 岩野 祥子, 渡邊 良平, 望月 輝一
2018年 33 巻 1 号 26-31
We developed a smartphone application named SmartPuncture to assist conventional CT-guided puncture without CT fluoroscopy, in this article we demonstrate the use and advantages of this application.
A puncture guideline is displayed by entering the angle into the application. Regardless of the angle at which the device is being held, the motion sensor ensures that the guideline is displayed at the appropriate angle with respect to gravity. The angle of the smartphone’s liquid crystal display (LCD) is also detected, preventing needle deflection from the CT slice image. Physicians can perform the puncture procedure by advancing the needle using the guideline while the smartphone is placed adjacent to the patient.
In an experimental puncture test using a sponge as a target, the target was punctured at 30°, 50°, and 70° when the device was tilted to 0°, 15°, 30°, and 45°, respectively. The punctured target was then imaged with a CT scan, and the puncture error was measured. The mean puncture error in the plane parallel to the LCD was less than 2°, irrespective of device tilt. The mean puncture error in the sagittal plane was less than 3° with no device tilt. However, the mean puncture error tended to increase when the tilt was increased.
This application can transform a smartphone into a valuable tool that is capable of objectively and accurately assisting CT-guided puncture procedures.
岩野 祥子, 福田 洋一, 石山 達也
2001年 110 巻 1 号 44-57
In order to evaluate the capability of one-dimensional microgravity investigations, we carried out two test surveys across the Katagihara fault in the southwest of Kyoto basin and the Fumotomura fault at the foothills of Suzuka Range. Since seismic reflection survey had already been carried out in these faults, the Bouguer anomaly due to the fault structures was expected in advance at an order of 0.1 mgal across the Katagihara fault and less than 0.1 mgal across the Fumotomura fault. It was also estimated that the spacing of the gravity points should be less than 50 meter to reveal the structures. We therefore conducted precise gravity measurements using a LaCoste & Romberg gravimeter (G-type) at about a 50 meter interval, and also carried out leveling surveys on the same points using a Wild NA3000 digital level. Moreover, we paid much attention for terrain corrections using the 50 meter DEM (Digital Elevation Model) provided by Geographical Survey Institute and partially using a 10 meter DEM compiled by ourselves. Consequently, we achieved 0.1 mgal level precisions for almost all the survey points. Using the gravity anomaly data, density structures in both survey areas were estimated and compared with the structures obtained from seismic reflection survey. The main results are as follows ; (1) comparatively simple structures are obtained to explain the gravity anomaly in the Katagihara fault, (2) the density contrast between the basement and the sedimentary layer is 0.58 g/cm3 in the Katagihara fault, (3) no gravity anomaly due to the displacement on the fault plain is observed in the Fumotomora fault, and (4) possibility of a high density layer is observed beneath the Tokai Group. Although the gravity survey has some limitations and drawbacks, it certainly gives us useful information about the density contrasts. Moreover, one-dimensional gravity survey is quite easy to conduct with very low cost. We therefore recommend that this kind of gravity surveys should be carried out whenever seismic reflection survey is conducted.
本多 亮, 河野 芳輝
2005年 51 巻 1 号 33-44
Accuracy of terrain correction strongly depends on the grid spacing of digital elevation dataset used for calculation. In and around the Japanese Islands, both 50 m mesh elevation on land area and 500 m mean bathymetric data on sea area are available. In order to simplify calculation algorithm, we firstly generated a synthesized digital elevation and bathymetry dataset whose grid spacing is approximately 50 meters by combining several available digital topographic data. We named this dataset the "Synthesized Land and Sea 50 M Mesh Topographic Data in and around the Japanese Islands-Version 2004; LS50MJ04", which has a size of about 14 GB for 2-dimensional array with 7 byte/grid. We coded a terrain correction programsimulating topography as an assembly of a rectangular parallelepiped prism and neglecting the curvature of the earth's surface. Integration of gravitational effects due to each prism on a station is truncated at 50 km. The accuracy of calculation is evaluated to be of the order of 1 mGal or less. We can calculate terrain corrections due to both land and seafloor topogra phies within one procedure. The calculated terrain correction values are more sensitive to short wavelength topographic undulations compared with our former ones, and are consistent with other works. We applied this program for nearly 600 thousands gravity measurements in and around the Japanese Islands.