Static laboratory earthquake measurements with the digital image correlation method

Vito Rubino, Nadia Lapusta, Ares J. Rosakis, Sebastien Leprince, & Jean-Philippe Avouac

Published 2015, SCEC Contribution #1810

Mapping full-field displacements and strains on the Earth’s surface during an earthquake is of paramount importance to enhance our understanding of earthquake mechanics. In this study, the feasibility of such measurements using image correlation methods is investigated in a laboratory earthquake setup. Earthquakes are mimicked in the laboratory by dynamic rupture propagating along an inclined frictional interface formed by two Homalite plates under compression, using the configuration developed by Rosakis and coworkers (e.g., Rosakis et al., 2007). In our study, the interface is partially glued, in order to confine the rupture before it reaches the ends of the specimen. The specimens are painted with a speckle pattern to provide the surface with characteristic features for image matching. Images of the specimens are taken before and after dynamic rupture with a 4 Megapixels resolution CCD camera. The digital images are analyzed with two software packages: VIC-2D (Correlated Solutions Inc.) and COSI-Corr (Leprince et al., 2007a). Both VIC-2D and COSI-Corr are able to characterize the full-field static displacement of a dynamic crack. The correlation analysis performed with either software clearly shows (i) the relative displacement (slip) along the frictional interface, (ii) the rupture arrest on the glued boundaries, and (iii) the presence of wing cracks. The obtained displacement measurements are converted to strains, using de-noising techniques; stresses are obtained by introducing Homalite’s constitutive properties. In a future study under preparation, the digital image correlation method is then used in combination with high-speed photography to capture the highly transient phenomena involved in dynamic rupture.

Rubino, V., Lapusta, N., Rosakis, A. J., Leprince, S., & Avouac, J. (2015). Static laboratory earthquake measurements with the digital image correlation method. Experimental Mechanics, 55(77).