Investigations on Processing of Seismic Wave Forms ( I ) Analysis of Wave Forms of a Compound Horizontal Component multiplied by a Vertical Component

Abstract

Because of various advantages, such as high recording density, versatility of processing of recorded waves, and possibility of repeating processes, magnetic tapes have been widely applied to recording seismic waves recently. On the other hand, they have the disadvantage that the information contained in them cannot be utilized without the process of playing them back. On the whole, however, exploitation of magnetic tapes for seismometry has bright prospects. Having this aim in mind, we are investigating methods of processing seismic waves recorded on magnetic tapes.
The procedures of analysis we are using now are as follows:
First: Estimation of apparent directions of epicenters of earthquakes making use of P wave train.
Second: Co-ordinate transformation of horizontal components of seismic waves to this apparent direction.
Third: Use of these compound components in combination with vertical components in order to discriminate S and other phases.
At present, the analogue processing is mainly used, but the digital processing is also being investigated for the purpose of ensuring more accuracy and precision and of repeating processes.
In this paper (Part I of the study), processing of seismic waves by means of co-ordinate transformation of horizontal components of seismic waves and by means of multiplication of the transformed components with vertical components is treated. The purpose of coordinate transformation in this report is to seek the incident direction of P wave by changing the direction of the seismometer equivalently in the electric circuit.