[S-CG45] Science of slow-to-fast earthquakes

[SCG45-P11] A new approach to visualize chemical reactions within fault slip zone: joint analysis of μXRF and μXRD to fault rocks

*Asuka Yamaguchi¹ (1.Atomosphere and Ocean Research Institute, The University of Tokyo)

Fault rocks are formed by mechanical and chemical processes within fault zones, and are expected to record slip parameters of ancient earthquakes. Observations in fault rocks are strongly scale dependent. In outcrop or drillcore, visual description would be performed to cm- to m- scale. On the other hand, microscopic description using thin section is limited to sub-cm. Geochemical analyses using SEM is limited to sub-mm order, whereas mineralogical analysis using conventional XRD requires ~0.1 g of powdered sample. Such scale dependence of observation inhibits multiscale understanding of fault rocks and distribution pattern of mechanical and chemical processes.
In recent years, development of X-ray analyses (μXRF and μXRD) enables non-destructive, wide-area, and microscopic compositional and mineralogical analyses. In this presentation I will introduce several examples of analytical results of fault rocks sampled from fossilized thrusts in on-land accretionary complexes (Shimanto Belt in Japan and Ghost Rocks Formation in Kodiak Island, Alaska) which records ancient subducion zone earthquakes, and discuss visualization of chemical reactions within fault slip zone.