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a b s t r a c tFundamental spatiotemporal field properties and particle velocity waveform signatures of subRayleigh and supershear ruptures were experimentally investigated through a series of laboratory earthquake experiments. We appeal to dynamic rupture theory to extract and highlight previously unnoticed aspects and results, which are of direct relevance to our new experiments. Kinematic relationships derived from both singular and non-singular solutions are applied to analyze and interpret various features observed in these experiments.A strong correspondence is demonstrated between particle velocity records obtained in lab experiments and synthetic particle velocity waveform profiles derived from theory. Predicted temporal profiles, sense of particle motion, and amplitude decay properties of sub-Rayleigh and supershear particle velocity waveforms are experimentally verified. In a particular set of supershear rupture experiments, the fault-normal (FN) and fault-parallel (FP) velocity waveforms were simultaneously recorded at fixed, off-fault field points as a shear Mach front swept these locations. Particle velocity records collected over a broad range of stable supershear rupture speeds validate the predicted scaling relationship δ δ β̇= − = u u V C / / 1 s s r s s 1 2 2 2 , between the FP δ (̇) u s 1 and the FN δ (̇) u s 2 velocity jumps propagated by a shear Mach front. Additional experimental findings include detailed rupture speed measurements of sub-Rayleigh and supershear ruptures and the observation of a supershear daughter crack with vanishing shear Mach front.Previously unappreciated scaling relations between particle velocity field components, attributed to dilatational and shear waves, are also developed and experimentally verified. In particular, the FP velocity jump δ̇( ) u x x , s 1 1 2 propagated by the shear Mach front, and the sliding speed δ̇( ) + u x , 0 1 1 , measured at a field point positioned extremely close to the frictional fault plane, are shown to obey a speed-dependent scaling relationship given by δ δ̇= − + u u / 1 2 s C s V r 1 1 2 2 , which was gleaned from a non-singular, steady state velocity field solution.

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A custom designed microtensile tester was integrated with an atomic force microscopy (AFM) to perform in situ tensile tests on two advanced metal evaporated (ME) magnetic tapes -ME/ polyethylene terephthalate (PET) (with PET as a substrate) and ME/polyethylene naphthalate (PEN) (with PEN as a substrate) where the tape surfaces were imaged simultaneously by AFM during tensile loading. The digital image correlation technique was used to process the AFM images and quantitatively measure local, nanoscale deformation for both front coat and back coat of the ME tapes subjected to uniaxial tensile loading. The surface morphology change, strain distribution evolution and crack initiation and propagation during tensile loading are discussed with the structures and mechanical properties of the ME tapes.