This book brings together state of the art, peer reviewed, papers on shear physics at the meso-scale in earthquake and landslide mechanics and is authored by leading international scientists. The Identification of meso-scale phenomena occurring between microscopic and continuum length scales has been one of the most exciting developments in the last decade in understanding shear between material interfaces as well as particulate systems and is considered as the bridge between the two length scales for studying material response. This area or research has broad applications to the fields of earth sciences and geo-engineering, with immediate bearing on our understanding of earthquake and landslide mechanics, two geological processes that pose great risk to man kind worldwide.