A Confidence Classification Scheme for P and S Suspension Logging Data

1. Home
2. Publications
3. Online Library
4. A Confidence Classification Scheme for P and S Suspension Logging Data

P- and S-wave velocities are used as input for key parameters for offshore foundation design, such as small strain shear modulus, and as input for enhancement of ultra-high resolution seismic (UHRS) reflection data, such as UHRS-derived cone resistance. P and S suspension logging (PSSL) is a common borehole geophysical logging technique performed for offshore geotechnical site investigations to derive these velocities. Recorded data acquired by PSSL require processing to derive interval velocities within a formation by determining arrival times of acoustic waves of interest at both receivers on the logging tool, i.e. arrival time picking of a trace pair. Recorded traces may be influenced by ground, borehole, and metocean conditions, as well as other factors which can affect interpretability. This paper presents a confidence classification scheme for PSSL data, whereby traces are manually assessed on the confidence of their interpretation. The classification scheme consists of four confidence levels: high, medium, low, and insufficient. A class is assigned at each test depth for each acquired wave type: P, S1-, and S2-wave. Four criteria are used for class determination: (1) first arrival visibility, (2) noise impact, (3) polarized behaviour (S-waves only), and (4) velocity repeatability. Trace data assessed as insufficient confidence are not considered for velocity processing. This classification approach has provided a practical framework for over 3000 test depths.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

2 - Site characterization, in-situ and laboratory testing, measurement