PASSIVE SEISMIC IMAGING USING MICROEARTHQUAKES

We have developed a method of processing seismic signals generated by microearthquakes to image local subsurface structure beneath a recording station. This technique uses the autocorrelation of the vertically traveling earthquake signals to generate pseudoreflection seismograms that can be interpreted for subsurface structure. Processed pseudoreflection data, from microearthquakes recorded in the island of Hawaii, show consistent reflectivity patterns that are interpreted as near-surface horizontal features. Forward modeling of the pseudoreflection data results in a P-wave velocity model that shows reasonable agreement with the velocity model derived from a refraction study in the region. Usable signal-to-noise ratio is obtained down to 2 s. A shear-wave velocity model was also generated by applying this technique to horizontal component data.