Temperature dependence of broadband seismometer sensitivity

TL;DR

This study develops a system to accurately measure the temperature dependence of broadband seismometer sensitivity, calibrates several models across a temperature range, and finds that sensitivity varies by about 0.11% per degree Celsius.

Contribution

The paper introduces a novel calibration system for measuring the temperature coefficient of broadband seismometers, enhancing accuracy in seismometer sensitivity calibration.

Findings

Temperature coefficient is approximately 0.11%/°C.

Phase delay variation is less than 2 ms across temperatures.

Frequency response below 1 Hz remains stable with temperature changes.

Abstract

Broadband seismometers are widely used in global observation networks deployed for geophysics research. Recently, the calibration of their sensitivity has become an important factor for ensuring observation accuracy. One of the limiting factors of calibration uncertainty is the temperature dependence of the sensitivity because seismometers operate in a wide range of temperatures. However, systems that accurately measure the temperature coefficient in seismometers have not been established. Herein, we develop such a system using a triaxial vibration exciter combined with a thermostatic chamber. Using this system, we calibrated several broadband seismometers (Trillium Compact, Trillium Horizon 360, and CMG-3T) at various temperatures, ranging from $-15 ^\circ$C to $+45 ^\circ$C. We found that the temperature coefficient was $(0.11\pm0.01)$ %/$^\circ$C, which can be attributed to the internal magnet of the seismometers. The variation of the phase delay corresponded to a change of less than 2 ms in output time delay. Additionally, we found that the relative frequency response below 1 Hz was stable against temperature variations. These values are useful for evaluating the measurement accuracy of seismometer observation networks.