High-resolution Automatic Microseismic Source Detections

Kirchhoff summation is one of the robust techniques to automatically scan for microseismic source locations. It does not require manual picking of P- and S-wave phase arrivals, but assumes the source location to have the largest stacked energy from all receivers. The energy focusing can be ambiguous if data have low signal-to-noise ratio or contaminations from undesirable phase arrivals such as scattered or converted waves. We propose a new high-resolution Kirchhoff summation to sharpen the focusing of the stacked energy objective function. This new approach divides the receiver array into a number of receiver groups. Each receiver group performs a conventional Kirchhoff summation (partial summation image) to improve the signal-to-noise ratio. The final stacked image is a multiplication of all partial summation images. Multiplication of partial images is the key to sharpen and to focus the stacked energy. We have successfully applied this new method on synthetic and microseismic field data and it outperforms conventional Kirchhoff summation by improving focusing and better differentiating overlapping or multiple events.