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Richard M. Allen (1), Guust Nolet (1), W. Jason Morgan (1), Kristin Vogfjord (2), Bergur H. Bergsson (3), Palmi Erlendsson (3), Gillian R. Foulger (4), Steinunn Jakobsdottir (3), Bruce R. Julian (5), Matt Pritchard (4), Sturla Ragnarsson (3), Ragnar Stefansson (3). (1) Dept. Geosciences, Princeton University, USA. (2) Orkustofnun, Reykjavik, Iceland. (3) Vedurstofa Islands, Reykjavik, Iceland. (4) Dept. Geological Sciences, University of Durham, UK. (5) U.S. Geological Survey, Menlo Park, CA, USA. _______________________________________ We present a 3D P- and S-velocity mantle tomographic image generated using mantle and core P and S body-wave phases. The data is from two years of magnitude > 5.5 events recorded on the PASSCAL-HOTSPOT and SIL networks, a total of over 60 stations deployed across Iceland. Preliminary results show a low velocity anomaly centered beneath central Iceland from 400km depth extending up to around 200km. This structure is similar to previous images however the amplitude of the S-velocity anomaly is about four times the P-velocity (rather than two times previously). At depth the anomaly is elongated north-south (~300km) relative to east-west (~200km). Our image differs significantly from previous images in the 0-200km depth range. The primary reason for this difference is that we first obtain a crustal model using local surface waves and then correct the teleseismic travel-times for the significant lateral velocity variations in the crust. When our knowledge of crustal structure is not used and station corrections applied as in previous studies, the velocity anomaly in the 0-200km depth range changes significantly. This suggests that velocity anomalies previously imaged in the uppermost mantle are in fact crustal anomalies being projected into the mantle. We are currently in the process of including long period surface waves to obtain absolute velocities in the uppermost mantle. We expect to present our final mantle images at the meeting. |