| Research Abstract |
Present project was executed with two purposes(1)to complete a gravity database to cover all over the area of Southwest Japan by developping the achievements of the former three projects(on the same category of Grant-in-Aid for Scientific Research(C) : No.01540331 in 1989-1991, No.04640400 in 1992-1994 and No.07640552 in 1995-1997), and(2)to publish the results obtained through those projects. This goal of our project was successfully achieved.
Gravity data in Southwest Japan have been accumulated and carefully compiled at Nagoya University from which we have completed an extensive and accurate gravity database. This database currently containes more than 146,000 of net gravity data collected from thirty nine institutes or otganizations, and it spatially covers whole the area of Southwest Japan with very densely distributed gravity data. There is no more any vacant area of gravity data except for limitted areas such as very high mountaineos zone. Collected data were all processed and ed
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ited by both Nagoya University and Hokkaido University. A unified processing of gravity data was performed on all the field data, and an overall revision was also made on all the data already published. The revisions performed are(1)normalization of the gravity values with an accuracy of about 0.2 mGal refening to the Japan Gravity Standardization Net 1996(JGSN96), (2)keeping the coordinae accuracy by an amount of 0.01 minute of arc for both latitudes and longitudes(less than 20 meters error of horizontal position), (3)keeping the altitude accuracy by an amount within a few meters error, and(4)revisions on the method for terrain correction and related data such as DEM data(KS-110-1)provided by Geografical Survey Institute. After performing those total revisions, we accomplished an overall accuracy of 1 mGal on all the data filed in the gravity database.
Completion of this high quality gravity database enables us to utilize it for more better understanding of Japanese Islands not only in geophysical meanings but also in the other fields of geo-sciences. For this aim, we publish the results of the Gravity Database in Southwest Japan we constructed. The list we prepared are(1)large sized precise gravity anomaly tnaps ; 5 sheets, (2)a couple of gravity data books listed coordinates, gravity, and related values in a digital form, and(3)their machine-readable CD-ROM form. Less
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