Selected Publications
A multi-channel approach for automatic microseismic event localization using RANSAC-based arrival time event clustering (RATEC)
In the presence of background noise and interference, arrival times picked from a surface microseismic data set usually include a number of false picks which lead to uncertainty in location estimation. To eliminate false picks and improve the accuracy of location estimates, we develop a classification algorithm (RATEC) that clusters picked arrival times into event groups based on random sampling and fitting moveout curves that approximate hyperbolas. Arrival times far from the fitted hyperbolas are classified as false picks and removed from the data set prior to location estimation. Simulations of synthetic data for a 1-D linear array show that RATEC is robust under different noise conditions and generally applicable to various types of media. By generalizing the underlying moveout model, RATEC is extended to the case of a 2-D surface monitoring array. The effectiveness of event location for the 2-D case is demonstrated using a data set collected by a 5200-element dense 2-D array deployed for microearthquake monitoring.
Submitted to Geophysical Prospecting, 2017.
Microseismic events enhancement and detection in sensor arrays using autocorrelation based filtering
Passive microseismic data are commonly buried in noise, which presents a significant challenge for signal detection and recovery. For recordings from a surface sensor array where each trace contains a time-delayed arrival from the event, we propose an autocorrelation-based stacking method that designs a denoising filter from all the traces, as well as a multi-channel detection scheme. This approach circumvents the issue of time aligning the traces prior to stacking because every trace’s autocorrelation is centered at zero in the lag domain. The effect of white noise is concentrated near zero lag, so the filter design requires a predictable adjustment of the zero-lag value. Truncation of the autocorrelation is employed to smooth the impulse response of the denoising filter. In order to extend the applicability of the algorithm, we also propose a noise prewhitening scheme that addresses cases with colored noise. The simplicity and robustness of this method are validated with synthetic and real seismic traces.
Accepted in Geophysical Perspecting, 2016.
