Story perspectives

Mangatangi Fault Added to NZ Database, Could Trigger M6.9 Quake

5/28/2026

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Summary

Story summary

Researchers confirm the Mangatangi Fault is active and recommend adding it to New Zealand’s Active Fault Database.
The 18.6-km fault could trigger a magnitude-6.9 quake with intensity 6-7 shaking across south Auckland, where buildings meet the lowest design standard.
Slip rates of 0.017–0.27 mm per year, paleoseismic evidence of two ruptures (within 11,100 years and about 12,000 years ago), imply an 8,100-year rupture interval and place Mangatangi Reservoir and outlet at seismic risk.

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Story summary

Researchers confirm the Mangatangi Fault is active and recommend adding it to New Zealand’s Active Fault Database.
The 18.6-km fault could trigger a magnitude-6.9 quake with intensity 6-7 shaking across south Auckland, where buildings meet the lowest design standard.
Slip rates of 0.017–0.27 mm per year, paleoseismic evidence of two ruptures (within 11,100 years and about 12,000 years ago), imply an 8,100-year rupture interval and place Mangatangi Reservoir and outlet at seismic risk.