ABSTRACT

Dr Yanbin Wang, GSECARS, Argonne National Laboratory, University of Chicago

Labquakes - nanoseismology and micromechanics of deep earthquakes

Deep-focus earthquakes have hypocenter depths exceeding 300 km and are commonly associated with subducted oceanic lithosphere. Several mechanisms have been proposed for their nucleation and propagation including solid-solid phase transitions, dehydration embrittlement, transformational faulting or anticrack faulting, and shear instability thermal runaway. Recent advances in controlled high-pressure deformation experiments using synchrotron radiation and acoustic emission (AE) monitoring at GSECARS beamlines of the Advanced Photon Source (Argonne National Laboratory, Chicago, IL) allow detailed studies of brittle failure of Earth materials at high pressure. We present new results of nanoseismology tracking in 4D mechanical instabilities induced by the transformation of olivine to spinel at transition zone conditions. Individual AE events (“labquakes”) can be detected down to magnitudes (Mw) of 10^(-10) that possess characteristics similar to real earthquakes. We also present similar results for eclogitization of metastable granulite at lower crustal conditions. Nanoseismology and postmortem microstructure characterization are combined to improve rupture nucleation and propagation models for both deep-focus and lower crustal earthquakes.