We can use geothermal energy by obtaining steam and/or hot water that are in subsurface fracture. Therefore, we should understand geometrial, mechanical, and chemical properties of the subsurface fracture so that we can use the geothermal energy. We can estimate location and structure of subsurface fracture by measurement of microseismic events that are emitted at the subsurface fracture. We have studied overlapping similar microseismic events. If a second event, with a similar waveform to an earlier event, arrives before complete attenuation of that earlier event, the two events overlap each other. We call the overlapping similar microseismic events "Proximate Microseismic Doublets". In this paper, we examine a theoretical method on relative source location of the proximate microseismic doublets.