Ground strains caused by rainfall observed at Yura, Wakayama Prefecture from 1979 to 83 have been investigated. Strains due to rainfall reach their peaks within a few hours (we call them F type) or rather long time (S type) after peaks of rainfall intensity. The F type appears when rainfall amounts exceed 30-40 mm. Initial loss of rainfall (rainfall amount from the beginning to the time when its effect appears on the strain record) shows no clear seasonal changes though large initial losses are sometimes seen from summer to the end of fall. The lapse time between two consecutive rains does not affect the initial loss of latter rainfall except the case of small lapse times such as within one or two days. Effect of rainfall on the strain is large when its initial loss is small, so that initial loss is literally the loss which should be eliminated from total amounts of rainfall for analysis of strains caused by rainfall.

View full abstract

Based on KIJKKAMÄKI's temperature model t=a+bz^c, the authors devised an experiment to test how KUKKAMAKI's corrections improved the discrepancy between fore and back leveling in actual leveling circumstances. Although KUKKAMAKI's c values obtained from temperature measurements were widely scattered, the correction using these c values could improve the discrepancy. On the other hand, the correction using c=-1/3 made the discrepancy larger than that without corrections. Additionally, it was found that terrain profile in a section was an important factor in applying refraction corrections.

View full abstract

Residuals of astronomical observations of longitude and latitude in Asia may be related with the secular variations of the z-component of the internal geomagnetic field in the 1970's near the Southeast Asia (MizuNo 1984). Variations of the internal field could be produced by convective motions in the fluid core. But heat transport from the fluid core into the mantle would not be enough to produce mantle plumes for a rapid variation. Local variations for periods of several years in longitude and latitude may be attributed to thermal expansion in the fluid core near the core-mantle boundary.

View full abstract

The barometric effects on the borehole tiltmeters have been investigated for the 19 instruments of the National Research Center for Disaster Prevention, which were installed in the Kanto-Tokai area, central Japan, for the research on the earthquake prediction. The result shows that the admittances of tilt to barometric pressure are about 1 × 10^-8 radian/hPa or less. These values are several times larger than the ones estimated by OOE and HANADA (1982) for Tohoku area and they have no systematic regional variation. For the several tiltmeters which have large admittances, the time variations of the admittance have been also examined using the records of three years. Some of them show the secular admittance changes within about two years after the installation of the instruments, while one of them shows a sudden admittance change between the periods before and after the re-installation of the instrument. These results suggest that the barometric influence on the tiltmeters is caused by the deformatin of the vessel due to the barometric pressure change, though it is not clear why some tiltmeters show the secular admittance changes after the installation.

View full abstract

[in Japanese]

View full abstract

We proved that Schreiber's rule is inapplicable to the adjustment of free-networks.

View full abstract

We construct the formulas of an extended Schreiber's rule for the adjustment of free-networks.

View full abstract

A temperature recording system for electrooptical distance measurements was developed. The system utilizes a portable computer and a integrated-circuit temperature sensor with an accuracy of ±0.1°C Temperature data stored in the system are transmitted to the host computer via RS-232C.

View full abstract