Geophysical imaging of the Quaternary Wairoa North Fault, New Zealand: a case study

摘要: Abstract An integrated geophysical investigation, including gravity, vertical electric sounding (VES), 2D resistivity and seismic reflection/refraction techniques, was carried out along two profiles across the extensional Wairoa North Fault, New Zealand, prior to a trenching paleoseismic study. The data clearly imaged fault plane lying directly beneath suspected scarp on one profile. location of intersection with surface deduced from 2.5D gravity modeling subsequently corroborated by within 5 m. A 60° dip (±10–20°) for both profiles, similar that revealed in trench, modeled about 70 m depth at locations, indicating minimum displacement. Seismic methods, together trial ground penetrating radar (GPR) profile, were less successful imaging deformation above plane, partly because lack coherent reflectors upper Quaternary sequence, but mainly deep weathering sides fault. Despite this deeply weathered environment, methods (especially resistivity) have proved very effective confirming significance scarp, facilitating accurate siting trench providing valuable deeper information morphology.