Capturing Uncertainties in Source-Specific Station Corrections Derived from a 3-D Model
Abstract
Uncertainties in Source-Specific Station Corrections (SSSCs) arise from several sources. If the SSSCs are constructed directly from empirical travel times, there are errors caused by origin time and hypocenter location errors, measurement errors, and phase misidentification. If a 3-D model is used either to interpolate an empirical surface or to compute the SSSC directly, then uncertainties in the 3-D model will also introduce errors in the SSSC. In order to capture the uncertainties in the SSSC that arise solely from the 3-D model, we trace rays through a large number of random model realizations and catalogue the fluctuations in the computed SSSCs. Each random realization of the 3-D model should fit the data used to construct the model and be drawn from information about the uncertainties at each point in the 3-D model, including both the vertical and horizontal correlation of the model uncertainties. We have made progress in estimating point-wise model uncertainties by performing a Monte-Carlo inversion of broad-band surface wave dispersion. The spatial correlation of uncertainties is more poorly known than the point-wise uncertainties, but we suggest that it is governed largely by the spatial correlation of the Earth itself. Therefore, with reasonable confidence we identify the correlation of the errors with the spatial correlation of the model. We describe the method used to generate the set of random models and report the first results of the application of this method to the CU-Boulder 3D model. Our results show that theoretical estimates of uncertainties are similar to those obtained using empirical information. We also demonstrate that the uncertainties in SSSCs depend strongly on the model properties, in particular the vertical velocity gradient and the horizontal correlation of the model errors.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2001
- Accession Number
- ADA529613
Entities
People
- L. F. Tenorio
- M. P. Barmin
- Michael H. Ritzwoller
- N. M. Shapiro
- P. B. Weichman
- W. C. Navidi
Organizations
- University of Colorado Boulder