Slow slip events (SSEs) accommodate a significant proportion of tectonic plate motion at subduction zones, yet little is known about the faults that actually host them. The shallow depth (<2 km) of well-documented SSEs at the Hikurangi subduction zone offshore New Zealand offers a unique opportunity to link geophysical imaging of the subduction zone with direct access to incoming material that represents the megathrust fault rocks hosting slow slip. Two recent International Ocean Discovery Program Expeditions sampled this incoming material before it is entrained immediately down-dip along the shallow plate interface. Drilling results, tied to regional seismic reflection images, reveal heterogeneous lithologies with highly variable physical properties entering the SSE source region. These observations suggest that SSEs and associated slow earthquake phenomena are promoted by lithological, mechanical, and frictional heterogeneity within the fault zone, enhanced by geometric complexity associated with subduction of rough crust.

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ZnO nanoblades and nanoflowers are synthesized using zinc acetate dihydrate Zn(CH3COO)2∙2H2O dissolved in distilled water by ultrasonic pyrolysis at 380–500°C. Thermogravimetry-differential scanning calorimetry, x-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and low-temperature photoluminescence (PL) were used to characterize the thermal properties, crystalline and optical features of the ZnO nanostructures. The results showed that at 400°C the formation of nanoblades resulted from the simultaneous precipitation and nucleation in zinc acetate precursor. At an elevated temperature of 450°C, decomposition was almost advanced and thus the size of nanopetal became smaller and aggregates became larger by as much as 60nm. The formation of aggregates is explained in terms of random nucleation model. Through PL measurement, nanoblade showed a strong near band-edge emission with negligible deep-level emission and free exciton band-gap energy Eg(0)=3.372eV and Debye temperature β=477±65K by the fitting curve of free exciton peak as a function of temperature to Varshni equation, Eg(T)=Eg(0)−αT2∕(β+T), which are very close to bulk ZnO.

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