Always finding faults: New Zealand 2016

Kevin W. Hall, Helen Isaac, Malcolm Bertram, Kevin Bertram, Don Lawton, Alexis Constantinou, Doug Schmitt, Randy Kofman, Jennifer Eccles, Vera Lay, Stefan Buske, John Townend, Martha Savage, Andrew Gorman and Richard Kellett

ABSTRACT

CREWES participated in two collaborative seismic programs that were conducted on the North and South Islands of New Zealand in early 2016. The South Island survey was conducted in the Whataroa Valley, primarily on unconsolidated glacial and river sediments, and consisted of a variety of vertical seismic profile (VSP) surveys in the DFDP-2b borehole, as well as surface 1C-2D, 1C-3D and 3C-3D surveys. The purpose of this survey was to better understand the Alpine Ffault, which runs along the west coast of the South Island and has potential to produce M8+ earthquakes.

The North Island survey was conducted along the top of a stop-bank over unconsolidated river and marine sediments in the Hauraki Rift, and consisted of a single 1C-2D crooked-line. One of the goals of this project was to test the viability of seismic reflection surveying to image faults using a Vibe in this area. This seismic line crosses the northern Kerepehi fault, which has previously been inferred from gravity data. The Kerepehi fault is considered to be active, and is thought to have produced M6+ earthquakes in the past.

This report shows an initial comparison of fiber-optic (DAS) and geophone results for a zero-offset VSP in DFDP-2b. We also present crooked-line (1C-2D) processing results, including stacked and migrated time and depth sections across both the Alpine fault and the Kerepehi fault.

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