In the aftermath of the 2010-2011 Canterbury and 2016 Kaikōura earthquakes, invasive seismic testing has become more commonly used in geotechnical earthquake engineering. However, several critical aspects of both data collection and data processing are not well understood by either the contractors collecting and processing the data or the geotechnical engineers using the data.

This report summarises the invasive seismic test methods typically used in New Zealand geotechnical engineering practice to measure VS and VP. It describes the test procedures and data processing that are generally accepted as ‘good practice’ – i.e., the procedures and processing that are necessary to obtain accurate and representative data that can be relied upon by geotechnical engineers for analysis and design. The report also describes the uncertainty inherent in the invasive seismic testing methods, including sources of uncertainty and how to quantify it. An example of an assessment of epistemic uncertainty using actual field data is provided, as are recommendations for what information should be included when reporting test results.