可変容量型ひずみ地震計および傾斜計による連続観測

Abstract

From the theoretical point of view it is clear that comparably large strain step will remainat the near field of focal region after the occurrence of an earthquake. To observe this strainstep quantitatively with high reliability, observational instruments must have the mechanicalstrength and the high sensitivity for long period waves. It can not be expected for the presenttiltmeters and extensometers to satisfy these conditions, therefore strain seismographs and tiltmetersof variable capacitance type were developed.The strain seismographs were setted up at Kamitakara station, and during about one year, various type fo seismic strain waves have been recorded. They are showed in four photographsand give some sugestions for the study of focal mechanism. For instance, these observed waveforms are in good accordance with the theoretical ones calculated from dislocation theory.The tiltmeters which have been newly designed are constructed from the vertical pendulumwith a short natural period (0.5 see) and the variable capacitance type transducer. Becauseof short natural period of the pendulum, the disturbances by the long period surface waves ofdistant shocks are negligible. The pendulum is suspended by a leaf spring of 60mm lengthand 0.1 mm thickness, therefore the instruments are very strong for the acceleration of shortperiod seismic waves.