1. A method for locating a microseismic event in a subsurface formation, comprising: receiving a microseismic signal at a detector; obtaining a velocity model representative of the subsurface formation, the velocity model comprising multiple velocity layers; for each of the multiple velocity layers in the subsurface formation, generating a separate estimated microseismic event location and microseismic event origin time; and selecting one of the estimated locations and times from among the different estimated microseismic event locations and event origin times using a parameter of the microseismic signal received at the detector.