Surface Wave Attenuation in the Tibetan Plateau from Ambient Noise
Abstract
In this project, we explore methodologies to extract amplitude information from the empirical Green functions (EGF) derived from ambient noise correlations and to map attenuation of surface waves. Our approaches are to combine theoretical derivations, numerical simulations, and practical considerations. A particular problem in retrieving amplitudes from noise is that the ambient seismic noise source is not uniform and changes with time. Theoretical insights show that even in the case of incompletely diffuse noise fields, we can robustly recover not just travel times, but also ray arrival amplitudes, the ambient field s specific intensity, the strength and density of its scatterers if any, and most importantly, attenuation. We propose two approaches: linear array methods and more general methods for 2D station networks. Numerical simulations show that amplitudes and attenuations can indeed be extracted from noise correlations for a linear array or for a more general 2D array. We propose a temporal flattening procedure to speed up convergence while preserving relative amplitudes. For real data, we propose an asynchronous temporal flattening procedure that does not require all stations to have data at the same time. Tests on real data suggest attenuations are extracted that are comparable with those from earthquakes.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 14, 2013
- Accession Number
- ADA623521
Entities
People
- Richard Weaver
- Xiaodong Song
- Xiaoning Yang
Organizations
- University of Illinois Urbana–Champaign