Estimating local V_p/V_s ratios within similar earthquake clusters

We develop and test a method to estimate local V_p/V_s, ratios for compact similar earthquake clusters using the precise P and S differential times obtained using waveform cross-correlation. We demonstrate how our technique works using synthetic data and evaluate likely errors arising from near-source takeoff angle differences between P and S waves. We use a robust misfit function method to compute V_p/V_s ratios for both synthetic data sets and several similar event clusters in southern California, and use a bootstrap resampling approach to estimate standard errors for real data. Our technique has higher resolution for near-source V_p/V_s ratios than typical tomographic inversion methods and provides constraints on near-fault rock properties.