ISO 16063-42:2014

Overview

ISO 16063-42:2014 defines a high-accuracy method for the calibration of seismometers using the local acceleration of gravity as the reference. The standard is aimed primarily at servo-type, wide-band seismometers (mass-position output, bandwidth ~0.003 Hz to 100 Hz) and enables determination of static sensitivity down to about 1 × 10−5 m/s² (1 mGal). It specifies instrumentation, environmental controls, calibration procedures, and the traceability routes needed to achieve internationally comparable sensitivity and uncertainty statements.

Key topics and technical requirements

• Calibration principle: Use of a precision tilt table to apply known vertical/horizontal acceleration components derived from the local gravitational acceleration g (a_v = cosθ·g, a_h = sinθ·g). Seismometer outputs are measured at multiple tilt angles to solve for sensitivity and bias.
• Traceability of g: Three accepted approaches:
  • Use of the International Gravity Standardization Network (IGSN‑71) values corrected for latitude/altitude.
  • Local measurement with a relative gravimeter tied to a reference point.
  • Direct measurement with an absolute (free-fall) gravimeter (best uncertainty).
• Achievable uncertainty:
  • Typical combined expanded (k=2) uncertainty of applied acceleration: ~0.1 mGal (1×10−6 m/s²).
  • With an absolute gravimeter: down to ~5 μGal (5×10−8 m/s²).
  • Relative calibration uncertainty (excluding DUT): ~0.5%.
• Environmental and apparatus requirements:
  • Reference conditions: ~100 kPa, 50 % RH, 23 °C (monitor temperature and pressure).
  • Rigid, heavy seismic block isolated from building motion.
  • Voltmeter relative uncertainty ≤ 0.1 %.
  • Tunable low-pass filter options: cut-offs 10, 30 (normal), 60 Hz; slope ≥ 24 dB/octave.
  • Tilt table resolution ≤ 0.05° and uncertainty < 0.03°. Alignment between sensitive axis and vertical must be < 0.03°.
  • Stable, low-noise power supply for DUT and measurement electronics.

Practical applications and users

ISO 16063-42:2014 is used where high-accuracy seismometer sensitivity is essential, including:

• Geophysics and earth sciences (research-grade seismic networks)
• Disaster prevention (landslide precursor monitoring)
• Civil engineering (structural health diagnostics, foundation soil assessment)
• Nuclear-test monitoring and seismic verification systems

Primary users: national metrology institutes, calibration laboratories, seismometer manufacturers, geophysical observatories, and civil or environmental engineering organizations requiring traceable, low-frequency acceleration calibration.

Related standards

• ISO 16063 series (methods for calibration of vibration and shock transducers)
• ISO 5347-5 (calibration by Earth’s gravitation)
• ISO/IEC Guide 98‑3 (GUM: Guide to the expression of uncertainty in measurement)

Keywords: ISO 16063-42:2014, seismometer calibration, local gravitational acceleration, tilt-table calibration, absolute gravimeter, traceability, uncertainty, wide-band seismometer, servo accelerometer.