Getting inside the earthquake machine: fine-scale imaging of the Alpine Fault zone

The Alpine Fault produces large earthquakes on average every 330 years, with its last rupture in 1717 AD. Studying a major fault this late in its cycle of stress accumulation is a unique opportunity to understand the subsurface conditions ahead of an anticipated large earthquake. The Deep Fault Drilling Project (DFDP) is an international research endeavour focusing on the structure, ambient conditions, and evolution of the central Alpine Fault via scientific drilling and multidisciplinary research. Although geophysical imaging has been successful at qualitatively mapping the Alpine Fault at large scales, we propose to fill the need to quantitatively interpret these signatures in terms of rock microstructure, geochemistry and fluid pressure-modulated processes occurring at the grain- and  fracture-scale by making systematic measurements of the microstructure and geophysical rock properties with novel laboratory techniques.

CATACLASITE SAMPLES:

We are studying the physical properties that control elastic wave speed in cataclasite samples. This is combined with CT image scanning, EBSD, petrography and XRD data. The figures below show waveforms through a cataclasite samples (right) and CT image of two of the samples (left). The sample diameter is 2.5 cm.

 

MYLONITE SAMPLES:

We are studying how texture and mineralogy influence the elastic wave anisotropy in the Alpine Fault Zone. We combine laser-ultrasonics, high-pressure transducer experiments with dynamic and static numerical modeling of anisotropy based on EBSD data.

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