Horizontal depth sections of V_p perturbations (upper row) and V_p/V_s ratios (lower row) after the inversion. The reference model (background model) is given in Table 1. V_p perturbations show the lateral variation of the subduction zone. The star indicates the 1999 August 20, M_w= 6.9 Quepos earthquake. Location of CCRDB indicated by dashed lines.