Numerical simulation of P-wave velocity structure of subduction zones

Numerical simulation shows that high velocity anomalies exist in most depth s of subduction zones with the maximum velocity at the depth of about 400km and 550km, which is consistent with the wave velocity structure determined by seismic tomography. Though resolution is low, seismic tomography shows the basic properties of P wave speed variation in subduction zones. The dat a from regional stations indicate that P-wave velocity anomalies can be pos itive or negative,in the range from - 10 % to 9 %. Low velocity anomalies e xist at the depth of about 700km, and metastable olivine causes low speed r egions that decline along the dip direction of subduction zones. Low resolu tion of seismic tomography is an obstacle to show detailed P-wave speed str ucture of subduction zones. To investigate fine structure of subduction zon es,we should use high-resolution data obtained from regional networks.