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SUMMARY:Validating the turbidite approach to paleoseismology using observa
 tions from the Mw7.8 Kaikōura earthquake\, New Zealand - Jamie Howarth (W
 ellington\, New Zealand)
DTSTART:20190116T110000Z
DTEND:20190116T120000Z
UID:TALK117193@talks.cam.ac.uk
CONTACT:Nienke Blom
DESCRIPTION:Turbidite paleoseismology is based on the along‐strike corre
 lation of deep-water turbidite deposits\, formed in response to earthquake
 -triggered strong ground motions. The approach has produced some of the lo
 ngest and most complete records of Mw7 to Mw9 earthquakes on subduction zo
 nes. However\, the veracity of the technique is still vigorously debated d
 ue to uncertainty in the relationships between fault source\, the spatial 
 distribution of ground motions and turbidite emplacement for a given earth
 quake. The debate can only be resolved by direct observations of these rel
 ationships that remain extremely rare. The 2016 Mw 7.8 Kaikōura earthquak
 e in New Zealand provides a unique opportunity to test the turbidite appro
 ach to paleoseismology because the fault source is relatively well defined
 \, ground motion models are well calibrated and post-event sediment cores 
 constrain the spatial distribution of turbidite emplacement. Turbidites re
 vealed in sediment cores from along the Hikurangi margin demonstrate near 
 ubiquitous triggering of turbidity currents in 11 discrete canyon systems 
 along the slope margin up to 110 km north of the rupture tip. The spatial 
 distribution of turbidite emplacement agrees well with ground motions pred
 icted by physic-based simulations and shows that the threshold required to
  emplace turbidites is a PGV ≥ 18 cm/s. Moreover\, grainsize pulsing at 
 the base of turbidites correlates well with PGV amplitude peaks above the 
 triggering threshold providing confirmation of the contentious hypothesis 
 that turbidite pulsing records information on earthquake seismograms. Ulti
 mately\, the relationships between turbidite emplacement\, ground motions 
 and fault source observed during the Kaikōura earthquake support the use 
 of earthquake-triggered turbidites as a reliable paleoseismic proxy.
LOCATION:Marine/Wolfson Building lecture hall\, Bullard Labs.
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