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Volume 18 (1972)
- Issue 4 Pages 161-
- Issue 3 Pages 99-
- Issue 2 Pages 49-
- Issue 1 Pages 1-
Volume 18, Issue 4
Displaying 1-7 of 7 articles from this issue
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Yukio HAGIWARA1972 Volume 18 Issue 4 Pages 161-171
Published: March 25, 1973
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSMolodenskii's solution of the geodetic boundary-value problem is approximately derived by means of G1, a kind of terrain correction to gravity anomaly. Although many geodesists have theoretically discussed G1 since Molodenskii's problem was introduced, a very few reports of practical computation of G1 have been presented. In the present paper, the author practically obtains G1 using the gravimetric and terrain data of Tanzawa Mountains. The conclusions obtained here are summarized as follows: (a) In numerical computations of G1, an integration range of 20 km from gravity station can effectively suppress errors under 0.5 mgals In case of a gently-sloping hill, an integration with a range of 10 km works well in accurately calculating G1. (b) The contribution of the inner zone of the integration range to G1 is so large, that detailed maps of topography and gravity anomaly in the inner zone are necessary for data-reading with high accuracy. (c) Gi mirrors short-wavelength free-air gravity or terrain relief. G1 can also be approximated by a quantity proportional to the vertical gradient of gravity (free-air) anomaly. (d) Assuming as a rough estimate, we see that G1 produces errors of about 6 cm at maximum in the height anomaly and about 10 sec in the gravimetric deflection of the vertical on Tanzawa Mountains. The error estimated in the deflection of the vertical is not small as compared with the astrogeodetic deflections observed in the neighborhood of this area.View full abstractDownload PDF (971K) -
Noboru INOUCHI, Hiroshi SATO1972 Volume 18 Issue 4 Pages 172-179
Published: March 25, 1973
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSThe sea-crossing levelling on Uraga Channel was carried out in September 1972 by the Geographical Survey Institute. One of the error sources of the measurement, which was made by th e way of trigonometric levelling, is the effect of the vertical deflection, that is the correction due to the geoid curvature. In this paper, the effect of the vertical deflection is discussed, standing in another point of view by Ramsayer.
The vertical deflection depends on the curvatures of the geoid and the ellipsoid, then, the curvature correction can be deduced from the vertical deflection.
When the curvature is a function of distances, the error is expressed by the formula, dh=1/6 q′/q2 S3, where q is the curvature of the geoid, q' is its first derivativeq and s is the distance between observed stations. In the case of the sea-crossing levelling on Uraga Channel whose distance is about 6.7 km, the error (dh) is estimated to be 2.8 mm. In the calculation, the vertical deflections of levelling stations were obtained by the interpolation method of the vertical deflection, using gravity anomalies data of Kanto district. It should be mentioned, however, that the error is concerned to the distance cubed (S3), so it has serious problems in the survey of long distance amounting to 30 km, such as on Tsugaru Channel.View full abstractDownload PDF (621K) -
Yoichiro FUJII, Katsumi NAKANE1972 Volume 18 Issue 4 Pages 180-190
Published: March 25, 1973
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSIn a previous paper, one of the present authors estimates the rate of secular change of gravity at 0.817, cgal/year along the high gravity anomaly zone in South-Western Japan, with some discussions on the interaction of oceanic lithosphere of the Philippine Sea Plate and continental lithosphere of the South-Western Japan . In comparing this order estimation with actually observed gravity change, we must notice the possibilitythat the observed gravity change can be several times higher than estimated one, because the estimated change is the mean value for long time geological duration andthe contemporary change is interseismic one. This point is first discussed in the presentpaper based on the observed crustal deformation accompanied by plates interaction, and some attempts were made to detected secular change of gravity along the northernboundary of the Philippine Sea Plate by a comparison of old and new observed gravityvalues. After analysing the various kinds of errors included in the gravity surveys that were carried out by the Geographical Survey Institute, we can conclude that the ob erved secular change of gravity of +0.13+0 .18 mgals for past ten years at the southern parts of Kii Peninsula and Muroto Promontory is real one. Detected secular changes of gravity at each gravity stations in those regions become gradually higher as the stations locate more close to the southern point of promontory in concordance with the distribution of Bouguer anomalies. This fact means that the high gravity anomalies found in the peninsula or promontory along the northern boundary of the Philippine Sea Plate are being formed even at contemporary time. In conclusion, the authors emphasize that the more study of secular change of gravi y accompained by plates interaction should be tried as one of the most important problems of geodesy in tectonic area such as Japan Island.View full abstractDownload PDF (1261K) -
Takehisa HARADA1972 Volume 18 Issue 4 Pages 191-193
Published: March 25, 1973
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESS -
Torao TANAKA1972 Volume 18 Issue 4 Pages 194-201
Published: March 25, 1973
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSEffects of oceanic tides on the earth tides observed at Barim in China, and Kamigamo, Osakayama, Kishu and Rokko in Kinki District, Japan have been estimated in a similar way as in the previous report. The effect of change of gravitational field caused by the mass re-distribution of the earth deformed by surface load, on the vertical deflection, has been taken into consideration, for oceans locating at distances farther than 30°, the Green′s function by I. M. longman has been used, and in the case of neighbouring sea (0<30°), the above effect has been estimated together with the attraction of loading sea water mass, according to the way by E. Nishimura, who calculated the amount of the vertical deflection, representing the total effect by (1-n) A (A being the vertical deflection by attraction of water mass) with the coefficient 1-n of 0.5. The diminishing factor γ obtained by Nishimura at Barim has been re-examined. If 1-n is taken to be 0.7, then γ of the EW component becomes to 0.69, which agrees fairly well with that expected for the Gutenberg earth model. Similar results have also been obtained for Kamigamo and Osakayama, from which we may conclude that n is about 0.3, which agrees well with the result by l. Rosenhead. In several components of earth tidal tilts and strains at Kamigamo, Osakayama, Kishu and Rokko, there are some remarkable discrepancies between the observed values and those calculated for the Gutenberg earth model. The reasons for them are discussed.View full abstractDownload PDF (1094K) -
Sinzi NAKAI, Norio SATO1972 Volume 18 Issue 4 Pages 202-208
Published: March 25, 1973
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSRecent gravity survey has proved that the Morioka-Sirakawa (Shirakawa) line, which locates on the western rim of Kitakami and Abukuma mountains and shows the characteristic steep gradient of Bouguer anomalies, is very clear near Mizusawa . Two dimensional analyses along the profile A (Fig.1) were made and the crustal section as shown in Fig. 5 has been obtained. This section is consistent with the geological and seismological points of view. The Morioka-Sirakawa line seems to reflet the faultlike structure of the upper crust.View full abstractDownload PDF (1287K) -
Keichi KASAHARA1972 Volume 18 Issue 4 Pages 209-213
Published: March 25, 1973
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSDownload PDF (497K)
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