Application of strain seismographs to the discrimination of seismic waves

abstract Examination of microseisms recorded by strain and inertial seismographs at Wichita Mountains Observatory (WMO) has shown that the outputs of vertical strain and vertical inertial seismographs when combined through a linear filter do not provide a significant improvement of the signal-to-noise ratio in the frequency range 0.2 to 10 Hz. However, the ability of a combination of horizontal strain and inertial seismograph outputs to azimuthally discriminate between long-period surface waves arriving simultaneously from different epicenters is successfully demonstrated. The predicted response of strain seismometers to earth motion is verified by the existence of the proper phase and amplitude relationship, and high coherence among selected seismographs for single-source signals.