Unit:
Κατεύθυνση Εφαρμοσμένη Γεωλογία - ΓεωφυσικήLibrary of the School of Science
Author:
Kalaitzis Konstantinos
Supervisors info:
Φίλιππος Βαλλιανάτος, Καθηγητής, Τμήμα Γεωλογίας και Γεωπεριβάλλοντος, ΕΚΠΑ
Original Title:
Αpplications of Αmbient Νoise Τomography in Νortheast Ιndia
Translated title:
Αpplications of Αmbient Νoise Τomography in Νortheast Ιndia
Summary:
In recent years, Ambient Noise Tomography (ANT) has become a reliable passive seismic method for constraining the seismic velocity structure of the Earth's subsurface. ANT uses surface-wave tomography derived from ambient seismic noise. This method capitalizes on the principle that cross-correlation of ambient seismic noise recorded at two stations produces a deterministic wavelet, approximating the Green's function of the medium between them. This empirical Green's function serves as an approximation of the seismic response. It is similar to one station acting as an impulsive source. The retrieved Green's function encodes the velocity structure between stations, allowing for the utilization of inter-station travel times for surface waves across the network in tomographic inversion. This enables the visualization of seismic velocity perturbations across the entire network.
This thesis utilizes ambient noise tomography to probe the shallow structure of a region in Northeast India. A shear wave velocity model was computed using ambient noise techniques on continuous seismic recordings from 340 seismometers over two periods, 30 days in January and 10 days in July 2022. This is achieved through a linear stacking approach, which enhances the signal-to-noise ratios of cross-correlation functions, thereby enabling the acquisition of reliable velocity measurements over various periods. A database of vertical component cross-correlation functions and corresponding Rayleigh wave group velocity dispersion curves has been comprehensively established.
Main subject category:
Science
Keywords:
Ambient Noise Tomography, Shear Wave Velocity Model, Large-N Seismic Network, Signal-to-Noise Ratio, Rayleigh Wave Dispersion
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Αpplications of Αmbient Νoise Τomography in Νortheast Ιndia Master Thesis Kalaitzis Konstantinos.pdf
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