Global-Scale P-Wave Tomography Designed for Accurate Prediction of Regional and Teleseismic Travel Times for Middle East Events
Abstract
A global-scale P-wave tomography model of the crust and mantle is constructed. The model depicts both large-scale tectonic/dynamic features, as well as detailed upper mantle heterogeneities beneath the greater Middle East region. Fully three-dimensional ray tracing is employed to achieve accurate travel-time predictions of a suite of P and Pn arrivals, necessitating the characterization of irregular and discontinuous boundaries. Therefore, we explicitly represent undulating seismic discontinuities in the crust and upper mantle within a spherical tessellation modeling framework. The tessellation-based model architecture is hierarchical in that fine node sampling is achieved by recursively subdividing a base-level tessellation. Determining the required node spacing to effectively model a given set of data is problematic, given the uneven sampling of seismic data and the differing wavelengths of actual seismic heterogeneity. To address this problem, we have developed an inversion process called Progressive Multi-level Tessellation Inversion (PMTI) that exploits the hierarchical nature of the tessellation-based design and is well-suited for modeling a mixture of teleseismic and regional data. PMTI allows the data to determine the level of model complexity by progressively solving for shorter wavelength structure, thereby robustly imaging regional trends and allowing localized details to emerge where resolution is sufficient. Using the PMTI approach, we have developed a global-scale P-wave model that simultaneously predicts teleseismic P and Pn travel times for events occurring throughout the Middle East. The tomographic image provides a new glimpse of the complex upper mantle velocity anomalies associated with the convergence of the Arabian and Indian plates with Eurasia along the Tethyan margin.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2010
- Accession Number
- ADA569592
Entities
People
- Gardar Johannesson
- Nathan A. Simmons
- Stephen C. Myers
Organizations
- Lawrence Livermore National Laboratory