Evidence of Seismic Slip on a Large Splay Fault in the Hikurangi Subduction Zone. (23rd August 2021)

• Record Type: Journal Article
• Authors: Coffey, Genevieve L.; Savage, Heather M.; Polissar, Pratigya J.; Meneghini, Francesca; Ikari, Matt J.; Fagereng, Åke; Morgan, Julia K.; Wang, Maomao
• Is Part Of: Geochemistry, geophysics, geosystems. Volume 22:Number 8(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-23
• Subjects: Hikurangi -- earthquake -- tsunami -- biomarker -- frictional heating -- seismic hazard; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 550.5
• DOI: 10.1029/2021GC009638
• Languages: English
• ISSNs: 1525-2027

Abstract

Abstract: The Hikurangi subduction zone is capable of producing moderate to large earthquakes as well as regularly repeating slow slip events. However, it is unclear what structures host these different slip styles along the margin. Here we address whether splay faults can host seismic slip at shallow (<1 km) depth by investigating the Pāpaku fault, sampled during International Ocean Discovery Program Expedition 375. We use biomarker thermal maturity to search for evidence of frictional heating within turbiditic sediments of the Pāpaku fault. Four zones of localized high temperature are found near the top of the fault zone, which are interpreted to be zones of localized seismic slip. Thermal modeling shows that the most likely maximum displacement on the shallow Pāpaku fault during each event was 14–17 m. Our results demonstrate that the Pāpaku fault, and potentially other splay faults along the margin, host coseismic slip and have the potential to produce large tsunami (e.g., runup heights of >1 m as observed in the 1947 Poverty and Tolaga Bay earthquakes. Key Points: Biomarker thermal maturity shows that the Pāpaku fault, a large splay fault of the Hikurangi subduction zone, has hosted large (∼> M w 7) earthquakes along multiple fault strands The Pāpaku fault and other splay faults along the Hikurangi margin are associated with high earthquake and tsunami hazard We document evidence of near‐seafloor, 14–17 m of earthquake slip in four areas within the upper 40 m of the fault zone