We have identified seismic phases reflected off the top and bottom of a low velocity layer (LVL) by analysis of seismograms from six small earthquakes in Hawaii. These events occurred almost directly beneath station AIN of the Hawaiian Volcano Observatory (HVO) seismic network, located within the Kaoiki seismic zone on the southeast flank of Mauna Loa. The polarity reversals of the first reflected phases provide clear evidence for the existence of a LVL beneath this station. The LVL is estimated to be at a depth of about 11.5 km, with a thickness of about 800 m. The estimate depth to the top of the LVL's consistent with the depth distribution of low-angle thrust faulting events from the aftershock sequence of the 1983 Kaoiki earthquake. Presumably, this zone is the marine sediment layer buried beneath the volcanic pile, along which the volcanic edifice may slip easily to cause large earthquakes. Mapping the interface between the volcanic pile and oceanic crust and thus determining the depth and thickness of the buried sediment layer is essential for understanding the tectonics of large earthquakes in Hawaii. ¿ American Geophysical Union 1989