3:30 PM - 3:45 PM
[MIS17-07] Exploring initiation of megathrust earthquake from rock friction experiments
Keywords:Rock friction experiment, Subduction zone, Megathrust earthquake, Accretionary complex
Coastal areas including Japan facing subduction zones have been subjected to strong ground motions and tsunamis due to megathrust earthquakes. To mitigate these disasters, it is necessary to understand the mechanisms of earthquake generation in subduction zones and the slip behavior of plate boundary faults. In addition, frictional behavior is strongly material dependent. Therefore, the mechanisms of earthquake generation in subduction zones cannot be understood without understanding the frictional behavior of the materials present at subduction plate interface.
At a trench, an incoming lithological package consisting of oceanic basalt, pelagic sediment, hemipelagic sediment, and trench-fill sediment from bottom to top, the so-called ocean floor stratigraphy, on a oceanic plate collides with a landward plate. Part of the ocean floor stratigraphy underthrusts along the plate boundary and the rest accretes at the landward plate, forming an accretionary prism. Plate boundary faults develop in the underthrust rocks of the ocean floor stratigraphy and cause megathrust earthquakes by their slips.
Each lithology of the ocean floor stratigraphy has a different mineral composition and, therefore, a different frictional behavior. Results from ocean drilling have shown that pelagic sediments rich in clay minerals play a significant role in the huge slip and tsunamis associated with a megathrust earthquake. On the other hand, the sources of megathrust earthquakes lie deeper than the depth that ocean drilling has ever reached. How and where does a megathrust earthquake initiate at this depth of the seismogenic zone? In this presentation, I will present results on the frictional properties of plate boundary faults at the seismogenic zone based on geological studies at on-land accretionary complexes and rock friction experiments on some lithologies of the ocean floor stratigraphy.
Rock friction experiments give us access to short-term processes of megathrust earthquakes from long-term processes preserved in on-land accretionary complexes from subduction to exhumation. I would like to highlight the uniqueness of rock friction experiments in linking geology and seismology, which are located at the two extremes of the time scale in earth science.
At a trench, an incoming lithological package consisting of oceanic basalt, pelagic sediment, hemipelagic sediment, and trench-fill sediment from bottom to top, the so-called ocean floor stratigraphy, on a oceanic plate collides with a landward plate. Part of the ocean floor stratigraphy underthrusts along the plate boundary and the rest accretes at the landward plate, forming an accretionary prism. Plate boundary faults develop in the underthrust rocks of the ocean floor stratigraphy and cause megathrust earthquakes by their slips.
Each lithology of the ocean floor stratigraphy has a different mineral composition and, therefore, a different frictional behavior. Results from ocean drilling have shown that pelagic sediments rich in clay minerals play a significant role in the huge slip and tsunamis associated with a megathrust earthquake. On the other hand, the sources of megathrust earthquakes lie deeper than the depth that ocean drilling has ever reached. How and where does a megathrust earthquake initiate at this depth of the seismogenic zone? In this presentation, I will present results on the frictional properties of plate boundary faults at the seismogenic zone based on geological studies at on-land accretionary complexes and rock friction experiments on some lithologies of the ocean floor stratigraphy.
Rock friction experiments give us access to short-term processes of megathrust earthquakes from long-term processes preserved in on-land accretionary complexes from subduction to exhumation. I would like to highlight the uniqueness of rock friction experiments in linking geology and seismology, which are located at the two extremes of the time scale in earth science.