Surface wave testing in Hamilton and Tauranga

Surface wave testing in Hamilton and Tauranga

In Hamilton, Andrew Stolte (QuakeCoRE), Seokho Jeong (University of Waikato) Ashley Cave (Masters Students, University of Waikato), and Sapol Raadnui (Visiting Research Intern, University of Auckland) conducted surface wave testing at a farm site in Ruakura (near the University of Waikato) to characterise the deep sedimentary basin in Waikato as a part of Seokho and Ashley-’s ongoing research. This testing included both active and passive surface wave testing methods, the multi-channel analysis of surface waves (MASW) and microtremor array measurements (MAM) methods, respectively. MASW testing is used to constrain the near-surface (depths less than approximately 30 metres) velocity structure using a linear array of 24 geophones, spaced at 2 meters. Using recordings of ambient vibrations, the MAM method is to characterise materials and develop spatially averaged shear wave velocity profiles at the site. The extent of the spatial averaging and the maximum depth of the profiles is constrained, in part, by the aperture of the 2D sensor arrays placed at the ground surface. At the Ruakura site, eight broadband seismometer stations were deployed in four circular arrays with 50-, 200-, 550-, and 1100-metre diameters.

In Tauranga, Andrew and Sapol conducted MASW and MAM at Blake Park, Tauranga Domain, and the Tauranga Boys College with support from Liam Wotherspoon (University of Auckland). At these sites, the MASW testing was performed using a linear array of 24 geophones, with a 2-metre spacing. Due to space constraints at the parks and school, two circular (50- and 150-m diameters) arrays of broadband seismometers were used for the MAM testing. During this testing, Andrew demonstrated the testing methods and discussed the dynamic site characterisation work in Tauranga with local practicing engineers.

Currently, the MASW and MAM field data is being processed to develop shear wave velocity profiles at the sites in Hamilton and Tauranga. For more information concerning the ongoing work in Hamilton, please contact Seokho Jeong or Andrew Stolte.

For more information concerning the ongoing work in Tauranga contact Liam Wotherspoon or Andrew Stolte.