Critical evaluation and geological correlation of teleseismic phase data from Indian seismological stations |
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| Authors: | G Mohan S S Rai |
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| Institution: | (1) National Geophysical Research Institute, 500 007 Hyderabad, India |
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| Abstract: | We evaluated the quality of seismic phase data from Indian seismological stations through the analysis of teleseismic travel
times reported during 1976–83 and infer that only WWSSN stations (NDI, SHL, POO, KOD) apart from GBA and HYB can be rated
satisfactory while the majority of stations (more than 40) produce very poor quality data sets. Detailed analysis of teleseismic
P-wave travel time residuals shows that while the average structure of the upper mantle beneath India has high velocity (negative
residuals) there are marked lateral variations. In particular, three zones of anomalous positive residuals (low velocity)
are observed: one beneath the north western part of the Deccan trap, the second covering the southernmost peninsula (granulite
terrain) and a third rather localized one, to the north of Delhi coinciding with Delhi-Haridwar ridge. New Delhi exhibits
strong negative residuals in the E-SE quadrant along with negative station anomaly, implying that it is underlain by an anomalous
high velocity crust/upper mantle. The negative residuals observed over India, continue beneath the Himalaya till the south
of Lhasa but change sign further northward, suggesting the northern limit of the Indian upper mantle structure. |
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| Keywords: | Phase data residuals seismology teleseisms |
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