## Estimating an accurate RMS velocity for locating a microseismic event

### John C. Bancroft

The location and clock-time of a microseismic event (x0, y0, z0, t0) can be computed analytically using the Apollonius method that requires the first arrival clock-times at four known receiver locations. The velocity is assumed to be known and constant. If the velocity is not known, it can be estimated by using an iterative technique that minimizes the error of the traveltimes between the source and receiver. Improving the accuracy of the velocity improves the estimate of the source location. The convergence to the correct solutions is dependent on the geometry of the source and receiver locations. ) can be computed analytically using the Apollonius method that requires the first arrival clock-times at four known receiver locations. The velocity is assumed to be known and constant. If the velocity is not known, it can be estimated by using an iterative technique that minimizes the error of the traveltimes between the source and receiver. Improving the accuracy of the velocity improves the estimate of the source location.