1985 年 38 巻 3 号 p. 359-364
A new system for the temporary observation of earthquakes have been developed. Analogue memories by CMOS-RAM and usual audio cassette stereophonic recorder are used for the system. They are well developed and cheap. Seismic wave signals and time code signals are holded in the memories by the trigger signal and recorded into a cassette as the audio signals converted by high frequency sampling clock. Multichannel observation is possible by the channel serial output.
Playback of signals is done by the simple memory system converting signals from audio frequency to the suitable frequency. Audio signal analyzers are also available for the direct playback signals of the tape recorder.
In the case of two-channels. recorder which wee call OM-2 type, , using WM-D6C recorder with Dolby-B noise reduction system, 46-db dynamic range can be gotten for each channel. We are observing microearthquakes at more than 20 temporary stations by the recorders with a high-gain and a low-gain channel for one component vertical senser to get records of microearthquakes and unsaturated records of largee shocks. About 900 eventss are stored in a 60 minutes cassette tape in this case.