The energy and trigger response of the Irvine-Michigan-Brookhaven detector at the time of supernova SN1987A has been studied further since the detection of a burst of neutrinos on 23 February 1987. Here we present improved measurements of the event energies and energy uncertainties, relative times, triggering efficiencies, and angles from the presumed source. The detector is found to have no significant directional bias against tracks moving in the direction toward the supernova. The statistical significance of the observed excess of events pointing away from the Large Magellanic Cloud is discussed.
