Publications

We investigate local variations of the P-wave velocity structure in the lower-most mantle (D") beneath Western Siberia. Data of earthquakes in the Kurile Island region recorded at short-period stations of the Israel Seismic Network show a high-amplitude phase (PdP) after P which cannot be explained by standard Earth models. We present evidence that this phase is a reflection from a low-velocity lamella in D". The best, locally valid, 1-D model consists of a low-velocity lamella 282 km (± 20 km) above the core-mantle boundary with a thickness of 8 km (± 3 km). The very high amplitudes of PdP cannot be reproduced by a 1-D model. The PdP observation reported here is a regional feature. The area north of it does not show a P-velocity anomaly, whereas further north positive jumps in P- and S-velocity have been documented. Our observation once more demonstrates the complexity of D".

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Thomas, C.; Weber, M.; Agnon, A.; Hofstetter, A. (1998): A low-velocity lamella in D". Geophysical Research Letters, 25, 15, 2885-2888.