*Article* **Application of Waveform Stacking Methods for Seismic Location at Multiple Scales**

**Lei Li 1,2,\*, Yujiang Xie 3 and Jingqiang Tan 1,2**


Received: 17 June 2020; Accepted: 12 August 2020; Published: 11 September 2020

**Abstract:** Seismic source location specifies the spatial and temporal coordinates of seismic sources and lays the foundation for advanced seismic monitoring at all scales. In this work, we firstly introduce the principles of di ffraction stacking (DS) and cross-correlation stacking (CCS) for seismic location. The DS method utilizes the travel time from the source to receivers, while the CCS method considers the di fferential travel time from pairwise receivers to the source. Then, applications with three field datasets ranging from small-scale microseismicity to regional-scale induced seismicity are presented to investigate the feasibility, imaging resolution, and location reliability of the two stacking operators. Both of the two methods can focus the source energy by stacking the waveforms of the selected events. Multiscale examples demonstrate that the imaging resolution is not only determined by the inherent property of the stacking operator but also highly dependent on the acquisition geometry. By comparing to location results from other methods, we show that the location bias is consistent with the scale size, as well as the frequency contents of the seismograms and grid spacing values.

**Keywords:** seismic location; microseismic events; waveform stacking; hydraulic fracturing; induced seismicity
