Ali Asghar Mottaghi
Rezapour - Institute of Geophysics, University of Tehran

Using the data base of Tehran Seismic Telemetry Network, from 1996 through 2006, we analyze the 9 stations reporting the most arrivals. For these stations and events within study area, we demonstrated that there is a need for consideration of systematically biases, with their importance to improve earthquake location accuracy at local / regional distances. On the other hand, this procedure is a way to identify "pathological" stations. Using such procedure, we obtain station offsets by fitting an azimuthally dependent equation. For these stations the results can be interpreted in terms of or attributed to several major factors. Some of these factors such as geology structure underneath the station, errors in instruments and unqualified analysts would be found. In this research local velocity curves for Pg, Pn, Sg, Sn phases of events within the study area , using the data base of last ten years, are obtained and computed the Vp/Vs ratio.