The upper mantle structure under South-East Europe derived from GRF broadband records of Greek earthquakes
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Vols. 1-18 (1924-1944), ISSN 0044-2801
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Abstract
Broadband recordings from the GRF (Grafenberg) Array of the strongest earthquakes from Greece are examined. A P-wave seismogram section of a number of events in the range between 1,300 and 2,100 km epicentral distance is constructed. The dominant feature in this section is the second arrival, which is the reflection from the 400 km discontinuity. Characteristic amplitude changes of this phase across the array are observed. The apparent velocity across the array of the first arriving P phase is very slow, indicating a slower upper mantle in SE Europe than in other regions. There is also a very weak indication of a third phase. The resulting model of the upper mantle, which was derived with the aid of theoretical seismograms, shows a pronounced discontinuity at a depth of 400 km. The time difference between the observed first two phases can be used for a fast estimation of the epicentral distance.
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