ECORD Distinguished Lecture
September 25, 2019 @ 1:00 pm - 2:00 pm
Subduction plate boundary faults are capable of generating some of the largest earthquakes and tsunami on Earth, such as the 2011 Tōhoku, Japan. However, in the last 15 years a new type of seismic phenomena has been discovered at subduction zones: slow slip events (SSEs), where slip occurs too slowly to produce seismic waves. SSEs may have the potential to trigger highly destructive earthquakes and tsunami on faults nearby, but whether this is possible and why SSEs occur at all are two of the most important questions in earthquake seismology today. IODP Expeditions 372 and 375 drilled the north Hikurangi subduction zone in New Zealand, where well-characterised SSEs occur every 1-2 years at depths of <2 -15 km below seafloor. The expedition installed two borehole observatories close to the patch of slow slip to investigate physical property changes over the slow slip cycle, and collected geophysical log and core data to characterize the sediment and rock types involved in slow slip. New seismic images (made using man-made acoustic waves) collected in 2017-2018 will in the future allow us to better understand the slow slip environment in 3D below and around the drill sites. In this presentation Rebecca Bell will discuss the objectives and preliminary findings of Expedition 372/375 and the recent seismic experiments, which aim to unlock the secrets of slow slip.