Performance characteristics of a rotational seismometer for near-field and engineering applications

Abstract

Based on the concept that torsion balances act as good filters for rotational oscillations at frequencies above their natural frequency of oscillations, we have fabricated a simple prototype to serve as a rotational seismometer for near-field and engineering studies. This instrument displays a nearly flat response at frequencies above 10 mHz, and the preliminary data taken with this instrument show a sensitivity of 5×10^-6(ν/0.01 Hz) rad sec^-1Hz^-½. Marginal improvements of the fabrication and housing will be needed to fully cover the sensitivities recommended by a U.S. Geological Survey (USGS) panel for studies at these frequencies.