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Volume 50 (2004)
- Issue 4 Pages 245-
- Issue 3 Pages 187-
- Issue 2 Pages 53-
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Volume 50, Issue 1
Displaying 1-6 of 6 articles from this issue
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Peiliang Xu2004 Volume 50 Issue 1 Pages 1-15
Published: March 25, 2004
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSTensors in the Earth Sciences are practically random, since they are either directly meas ured or indirectly inverted from other types of geo-measurements. Although random tensors have its root in multivariate analysis and nuclear physics, they are now actively investigated more as an independent topic of research; the results of random eigenvalues and eigenvectors from these investigations are mainly of asymptotic nature . In the Earth Sciences, an early result on random tensors was the accuracy of the random spectra of a random stress/strain tensor with a first order approximation. Recently, we have been working on random stress/strain tensors, the results from which are clearly borne in mind for use in the Earth Sciences . The purpose of this paper is to briefly summarize the progress of our recent studies of random second-rank symmetric (SRS) tensors. More specifically, we will mainly focus on: (i) the exact distribution of the random spectra, which is numerically manageable since the dimension of tensors of geo-interest is low; (ii) the biases of the random spectra, which are physically important but not investigated; and (iii) the accuracy of higher order approximation, which is needed if the ratio of signal to noise in stress/strain measurements is not sufficiently large. Since the eigenvector parameters are as important as the eigenvalues in the Earth Sciences, for example, in inferring fault strength and earthquake dynamical simulations, we have been paying due attention to them. On the other hand, we often encounter constrained tensors (deviatoric stress/strain tensors, pure shear tensors and seismic moment tensors, for example) in the Earth Sciences. Thus we also include the spectral theory of constrained random SRS tensors.View full abstractDownload PDF (1507K) -
Yuki Kobayashi, Sachiko Iwano, Yoichi Fukuda2004 Volume 50 Issue 1 Pages 17-26
Published: March 25, 2004
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSIn 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 .View full abstractDownload PDF (4423K) -
Mikio Tobita, Hiroshi Munekane, Masaru Kaidzu, Shigeru Matsuzaka, Yuki ...2004 Volume 50 Issue 1 Pages 27-37
Published: March 25, 2004
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSThe 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.View full abstractDownload PDF (3383K) -
Akio Kobayashi, Akio Yoshida2004 Volume 50 Issue 1 Pages 39-42
Published: March 25, 2004
Released on J-STAGE: September 07, 2010
JOURNAL FREE ACCESSWe investigated crustal deformation after the 1946 Nankai earthquake using tide gauge records. Although resolution of tide gauge records is not so high for seeing the temporal change in detail, vertical crustal movements whose relaxation times are between several months to years can be detected by them. It was reported that there had been a postseismic crustal deformation with a time constant of 4-5 months in southern Kui Peninsula (Kobayashi et al., 2002). In this paper we show that crustal deformations with a longer relaxation time of a few years were observed in northern Shikoku, examining tide gauge records at such stations as Takamatsu, Sumoto and Kobe. These observations suggest that there was a time lag in the development of postseismic slip between shallow and deeper parts on the plate interface after the Nankai earthquake.View full abstractDownload PDF (561K) -
-Comparing with the Precise Leveling in Omaezaki-Wu Xinhua, Shujiro Nishi, Tetsuro Imakiire, Minoru Tanaka2004 Volume 50 Issue 1 Pages 43-46
Published: March 25, 2004
Released on J-STAGE: July 05, 2011
JOURNAL FREE ACCESSGPS continuous observation and repeated pre cise leveling between Kakegawa and Omaezaki, Tokai area, Japan, have been carried out by the Geographical Survey Institute for detecting verti cal deformation and identifying its noise charac teristics. Comparing relative height differences obtained from two different observations with each other, it is made clear that the annual change in leveling result is in phase with that of zenith analysis, but the amplitude of the former is twice larger than that of tropospheric ZTD. In contrast, it is found out that the linear subsidence rate given by GPS is a little larger than that from leveling.View full abstractDownload PDF (2684K) -
2004 Volume 50 Issue 1 Pages 47-48
Published: 2004
Released on J-STAGE: March 01, 2011
JOURNAL FREE ACCESSDownload PDF (223K)
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