There is a need to perform modal analysis upon large structures such as buildings and bridges to understand and predict their behavior during earthquakes. Conventional holographic techniques cannot practically be used. Time average holography on glass plates and thermoplastic film requires vibration isolation. Double pulse holography on glass plates is time consuming in the processing of the plates and locating resonance frequencies and requires an in field darkroom. Conventional electronic speckle pattern interferometry (ESPI) normally requires vibration isolation and is limited to frequencies above 30 hertz. And also ESPI normally produces undesirable noisy looking images. Techniques for performing double pulsed ESPI with fringe enhancement and no vibration isolation have been developed to study these large structures. The work in progress on these techniques is presented.
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