Assessing Data Integrity in Seafloor Geodesy: An Analysis of Self-Calibrating Pressure Data Collected by Ocean Networks Canada

Precise seafloor geodetic measurements are essential for understanding plate tectonics, earthquake cycles, and volcanic activity. Seafloor pressure gauges provide a key tool for monitoring vertical changes in the seafloor elevation. However, distinguishing millimeter-scale tectonic signals from instrumental drift and environmental noise remains a fundamental challenge in deep-ocean observing.

This presentation evaluates the performance and data integrity of self calibrating bottom pressure recorders (BPR) deployed by Ocean Networks Canada (ONC) offshore Vancouver Island. Instruments like the RBR BPRZero and the Sonardyne FETCH AZA utilize Ambient-Zero-Ambient (AZA) in-situ calibration mechanisms to quantify sensor drift. The AZA method involves switching a pressure gauge from ambient (seafloor) pressure to atmospheric pressure within the instrument's housing. By comparing this internal pressure reading to an accurate barometer also measuring internal pressure, the drift can be precisely determined and a calibration function applied.

A forensic analysis of the dataset reveals that, while the high-resolution pressure measurements capture true genuine environmental signals, they are also significantly contaminated by instrumental artifacts that are partially related to the measurement approach itself. In this study we report findings from preliminary deployments and discuss the methodological challenges encountered, proposing mitigation strategies for future applications.