A relation between the earthquake magnitude and the elastic after -effect of the earthquake region is studied. The data used in this study are mostly obtained at Japanese crustal movement stations . It is found that a logarithm of the time constant of the after-effect is proportional to the earthquake magnitude.

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A “roller” extensometer was calibrated using a Michelson-type interferometer with a He-Ne laser source. This calibration system was capable of detecting relative displacements smaller than 0.016μm. The super-invar rod of the extensometer was displaced longitudinally about 2-7μm with a heating element consisting of a wire-wound bar of glass and a reflecting aluminum plate. The resultant displacement was detected by reading the fringe displacement records which had been converted photo-electrically by two differential photodiodes . As a result of this calibration, it was found that the sensitivity of the “roller” extensometer, which had been calculated from the radius of a roller and the optical length, was about 3560% of the true value for the range of the relative displacement amplitude of ±1-3μm.

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The paper reports long-term tiltmeter observations at the Matsuyama Crustal Movement Observatory, Shikoku, Japan, since 1949, with special reference to the postseismic land movement following the Nankaido earthquake of 1946. The land tilting there has accumulated in a general trend of the NNE-down sense, amounting to 3 sec (in arc) or more in the past twenty-five years. More precisely, the tilt accumulation was almost monotonous in the N-S component, whereas in the E-W component, its sense was reversed from E-down to W-down about 1956-7. These modes of tilting seem to harmonize with the regional land movement as derived from levelling data in the Shikoku district. The sea-level changes at three mareographic stations, Matsuyama, Uwajima and Tosa-Shimizu, all in west Shikoku, suggest slow postseismic movement in the Uwajima-Tosa-Shimizu area. Thus, aseismic local fault slip following the 1946 quake is hypothesized in order to interpret this remarkable effect. Tiltmeters have recorded short-term disturbances of unknown causes, occasionally. Comparison of these events with the sequence of local earthquakes of considerable magnitude (M=3.3-6.6) sometimes indicates chronological coincidence of the two sorts of events. But further investigation must be developed to draw a conclusion. Brief discussion is added on the stability of a float-type water-tube tiltmeter, in which a test observation has been made since 1972 successfully.

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A possibility of ionization by precipitation of high energy particles is examined using phase records of the NLK radio signal (18.6 KHz) transmitted from Jim Creek, Washington, U.S.A.. The NLK is received on a path, about half of which goes near the polar cap region, and often shows anomalous phase changes (SPA's) during geomagnetic storm periods. SPA's are investigated by using data obtained from the reception of NLK during 25 months from August 1970 to December 1973 with a point of view of associating SPA's at night with 24 geomagnetic storms whose horizontal components are greater than 100 γ observed at the Memanbetsu Magnetic Observatory of Japan . The results obtained for nocturnal periods are; a) Phase of NLK wave are advanced by 10 μs associated with decrease of horizontal component of 70 γ at the main phase. b) Phase change occurs 2 hours later than the main phase of a geomagnetic storm and continues for about 2 days but weak effect continues for about 5 days .

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　震源パラメーターの知られている地震に対し,極運動の励起函数を計算し,それを極座標に表現してみた・結果は,地震は直接チャソドラー運動を励起できないにしても,平均極の永年変化の原因を調べるときは見過すことはできないことを示している.

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