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| | Abstract | | Anomalous coherence functions, and as consequence strange SPAC coefficient curves were detected during the processing of data in Kathmandu Basin, Nepal for exploring deep sedimentary layers using long period microtremor. This anomaly is abrupt sag of the coherence functions that result in a winding dispersion curves of Rayleigh waves at around the period of the predominant peak of the power spectra and that of Horizontal-to-Vertical-Spectral-Ratio. In some station pairs of long distance, the bottom of sags reached to -0.6 The distorted dispersion curves can be interpreted as the influence of the first higher mode. By elimination of disturbed part, the inversion could be done and the results consistent with existing information were given. However, more detailed investigation seems necessary in consideration on wave generation and propagation because this doesn't explain the sag of the coherence function. |
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