| dc.description.abstract | Subduction zones are known to produce large, damaging earthquakes, but they can also experience slow-slip events which cannot be felt by humans. Understanding the mechanisms which influence this variation in slip rate will allow us to better anticipate how the subduction zone will act in the future. While the seafloor sediments make up a small portion of the subducting oceanic plate, they can have a noticeable impact on its ability to produce both large earthquakes and slow-slip events. Cores containing sediments and basement rock recovered by the International Ocean Discovery Program (IODP) from the Hikurangi Subduction zone near New Zealand were scanned using X-ray fluorescence (XRF) to obtain their chemical composition. Using the XRF data with in-situ measurements of porosity, p-wave velocity, and drilling parameters, as well as lab tests to determine the strength of these rocks, we can evaluate how the composition of the sediments affects their physical properties. A strong correlation between calcium content, porosity, and p-wave velocity was seen for the volcaniclastic cores. There is also evidence to suggest that the torque on bit during drilling is an indication of rock strength as it changes sharply at certain lithologic boundaries. Triaxial compression tests in the lab were used to quantify the rock strength of the volcaniclastic materials. This investigation into the subducting sediment properties builds onto pre-existing studies into the effects of seamounts on subduction and the factors that influence the slip rate at subduction zones. | |
