著者

小菅 正裕 池田 仁美 鎌塚 吉忠 佐藤 裕

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.32, no.4, pp.290-302, 1987-03-25 (Released:2011-07-05)

参考文献数

17

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A fault model of the 1983 Nihonkai-chubu (Japan Sea) earthquake (MJMA 7.7) was investigated on the basis of aftershock distributions, crustal deformation, and tsunami data. Since the earthquake took place under the sea off the coast of northwestern Tohoku District, there are a few land observation of crustal movement near the source area. We, therefore, have estimated the static fault parameters by comparing the wave form of observed tsunami with that of calculated from the static fault model. Trial fault parameters were derived from seismic data: focal mechanism solutions, seismic moment, and aftershock distributions with reference to the rupture process of the main shock. Our model was characterized by three fault planes trending NNE-SSW in the southern and the middle parts and NNW-SSE in the northern part, and by their low dipangle of 25°. The tsunami wave form was simulated numerically by a finite difference method. The fault model derived from seismic data reasonably explains the geodetic data and tsunamis. The calculated vertical deformation of land was consistent with the observed subsidence of 30-40 cm at Kyuroku island situated near the source area, and those of a few centimeters at Oga peninsula and Fukaura. The tsunami wave form observed at tide-gage stations along the coast of the Japan Sea was well simulated by our model as well as the model with higher dip angle. The data of strain step observed by extensometers installed in northern Japan support the low angle thrust event.

著者

小林 佑輝 岩野 祥子 福田 洋一

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.50, no.1, pp.17-26, 2004-03-25

著者

岩野 祥子 福田 洋一

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.46, no.2, pp.149-152, 2000-06-25

被引用文献数

3

著者

小林 裕太 日置 幸介

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.58, no.2, pp.89-93, 2012 (Released:2013-02-26)

参考文献数

16

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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.

著者

小林 昭夫 吉田 明夫

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.50, no.1, pp.39-42, 2004-03-25 (Released:2010-09-07)

参考文献数

11

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We 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.

著者

小林 昭夫 真砂 礼宏 吉田 明夫

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.48, no.1, pp.1-12, 2002-03-25 (Released:2011-03-01)

参考文献数

28

被引用文献数

1

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We examined tide gauge records at stations in and around the Kui peninsula to find if a precursory crustal deformation occurred before the 1946 Nankai earthquake. First, we removed effects of atmospheric pressure and astronomical tide on the records. Then, we tried to get rid of the effects of the oceanic current by taking the difference of the records betweentwo stations. After these corrections we found that sea level at Uragami where is located on the southeastern coast of the Kui peninsula had risen about 10 cm just before the Nankai earthquake. The sea level change, if we consider that to represent real subsidence of land near Uragami, could be explained by supposing that a slow fault slip corresponding to moment magnitude 6.9 occurred on the plate boundary in the offing of southeast of the Kui peninsula near the hypocenter of the Nankai earthquake.

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.22, no.2, pp.65-76, 1976-09-25 (Released:2010-09-07)

参考文献数

11

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A new gravimetric network, named the Japan Gravity Standardization Net 1975 (JGSN 75), was established and new gravity values were determined on the basis of the International Gravity Standardization Net 1971 (IGSN 71). A reliable gravimetric net has been organized in Japan by combining results of the GSI pendulum and gravimeter measurements by the Geographical Survey Institute and gravity values were determined in the Potsdam system referring to the value at the old pendulum station in Tokyo. The IGSN 71 published in 1974 contains 16 common stations with the national net. If the old reference value in Tokyo has no error, a discrepancy in gravity values at every common station must be equal to -14.0 milligals; a correction to the Potsdam absolute value. The present comparison showed that the discrepancy took mostly a constant value within a range of ±0.06 milligals. The mean value and the standard deviation were -13.80±0.03 milligals for the most districts and -14.00±0.03 milligals for the Kyushu District. No systematic inclination against the gravity value was found. This means that the scale of the Japanese gravimetric net agrees well with that of the IGSN 71. Therefore, the gravity value hitherto adopted in Japan can be converted into new one based on the IGSN 71 only by adding a constant value. New gravity values were obtained for 122 stations throughout the country and are given in this report. These are the results of repeated measurements including many new ones with LaCoste & Romberg gravimeters of which calibration constant values were corrected with our pendulum or the IGSN 71 results. A relative accuracy in this net is considered to be ±0.035 milligals and an absolute accuracy is the same as that ofthe IGSN 71. The JGSN 75 will serve as the framework of the gravimetric net in the country and should be used for all gravity works. The old Potsdam system values in Japan should be changed into new ones based on the JGSN 75.

著者

飛田 幹男 河瀬 和重 政春 尋志

出版者

日本測地学会

雑誌

測地学会誌 (ISSN:00380830)

巻号頁・発行日

vol.55, no.3, pp.315-324, 2009 (Released:2012-03-28)

参考文献数

10

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Three equations for meridional distance from the equator are compared. Accuracies, advantages and disadvantages are discussed. Conventional equation with higher terms has enough accuracy and slow convergence. Bessel’s simple equation is very easy for computer programming and has the fastest convergence and the fastest calculation speed. An analytic equation derived from elliptic integrals is easy for programming and has fast convergence and the highest accuracy.