Improvements in absolute seismometer sensitivity calibration using local earth gravity measurements

Bulletin of the Seismological Society of America
By: , and 

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Abstract

The ability to determine both absolute and relative seismic amplitudes is fundamentally limited by the accuracy and precision with which scientists are able to calibrate seismometer sensitivities and characterize their response. Currently, across the Global Seismic Network (GSN), errors in midband sensitivity exceed 3% at the 95% confidence interval and are the least‐constrained response parameter in seismic recording systems. We explore a new methodology utilizing precise absolute Earth gravity measurements to determine the midband sensitivity of seismic instruments. We first determine the absolute sensitivity of Kinemetrics EpiSensor accelerometers to 0.06% at the 99% confidence interval by inverting them in a known gravity field at the Albuquerque Seismological Laboratory (ASL). After the accelerometer is calibrated, we install it in its normal configuration next to broadband seismometers and subject the sensors to identical ground motions to perform relative calibrations of the broadband sensors. Using this technique, we are able to determine the absolute midband sensitivity of the vertical components of Nanometrics Trillium Compact seismometers to within 0.11% and Streckeisen STS‐2 seismometers to within 0.14% at the 99% confidence interval. The technique enables absolute calibrations from first principles that are traceable to National Institute of Standards and Technology (NIST) measurements while providing nearly an order of magnitude more precision than step‐table calibrations.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Improvements in absolute seismometer sensitivity calibration using local earth gravity measurements
Series title Bulletin of the Seismological Society of America
DOI 10.1785/0120170218
Volume 108
Issue 1
Year Published 2017
Language English
Publisher Seismological Society of America
Contributing office(s) Geologic Hazards Science Center
Description 8 p.
First page 503
Last page 510