Regional Analysis of Lg Attenuation: Comparison of 1-D Methods in Northern California and Application to the Yellow Sea/Korean Peninsula
Abstract
The measurement of regional attenuation Q(1) can produce method dependent results. The discrepancies among methods are due to differing parameterizations (e.g., geometrical spreading rates), employed data sets (e.g., choice of path lengths and sources), and methodologies themselves (e.g., measurement in the frequency or time domain). We apply the coda normalization (CN), two-station (TS), reverse two-station (RTS), source-pair/receiver-pair (SPRP), and the new coda-source normalization (CS) methods to measure Q of the regional phase, Lg (Q(Lg)), and its power-law dependence on frequency of the form Q(Of) with controlled parameterization in the well-studied region of northern California using a high-quality data set from the Berkeley Digital Seismic Network. We test the sensitivity of each method to changes in geometrical spreading, Lg frequency bandwidth, the distance range of data, and the Lg measurement window. For a given method, there are significant differences in the power-law parameters, Q(o) and eta, due to perturbations in the parameterization when evaluated using a conservative pairwise comparison. The CN method is affected most by changes in the distance range, which is most probably due to its fixed coda measurement window. Since, the CS method is best used to calculate the total path attenuation, it is very sensitive to the geometrical spreading assumption. The TS method is most sensitive to the frequency bandwidth, which may be due to its incomplete extraction of the site term. The RTS method is insensitive to parameterization choice, whereas the SPRP method as implemented here in the time-domain for a single path has great error in the power-law model parameters and eta is greatly affected by changes in the method parameterization. When presenting results for a given method it is best to calculate Q(of) for multiple parameterizations using some a priori distribution.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2007
- Accession Number
- ADA518897
Entities
People
- Douglas S. Dreger
- Kevin Mayeda
- Luca Malagnini
- Sean R. Ford
- W. S. Phillips
- William R. Walter
Organizations
- Lawrence Livermore National Laboratory