Instrument self-noise and sensor misalignment

Abstract. In this study we investigate self-noise of RefTek^TM 151-60A "Observer" broadband seismometers (flat to velocity between 50 Hz down to T₀=60 s, f₀≈17 mHz) using the coherency analysis method introduced by Sleeman et al. (2006).

We present a self-noise model for this type of sensor and compare it to the self-noise models of the standard observatory sensor STS-2 (Streckeisen) and RefTek's 151-120 broadband seismometer, which both have natural periods T₀ of 120 s.

We further report on the sensitivity of this technique to sensor misalignment and our success of eliminating leakage of the omnipresent microseism noise into self-noise estimates by numerically rotating seismic traces in order to find real self-noise.