Congcong Yuan , Song Han, Jie Zhang

The construction of accurate anisotropic velocity models for the monitoring region plays a very important role in microseismic monitoring. Due to ignorance of anisotropy, serious distortions may happen in the results of microseismic location and interpretation. Several effective methods have been developed to invert for VTI parameters and event locations using microseismic traveltime, while the results have a strong dependent on the initial velocity model and enough ray coverage due to strong nonlinearity of the problem. Meanwhile, microseismic waveform inversion for anisotropic parameters is still challenging because of low signal-noise ratio (SNR) of the data and high computation cost. Based on the assumption of small horizontal velocity variation, we develop a method jointly inverting event locations and velocity updates using traveltimes and vertical slowness estimates. The vertical slowness estimates are independent of the source information and easy to be obtained. We apply the method and currently developed method into four synthetic examples under different circumstances, the comparison demonstrates that our method is more stable than the other one, especially under the poor coverage. In addition, the field data test indicates that our proposed approach constrains the event locations better comparable to the other method.