Building and Testing an a priori Geophysical Model for Western Eurasia and North Africa

Abstract

We construct and evaluate a new three-dimensional model of crust and upper mantle structure in Western Eurasia and North Africa (WENA) extending to 700 km depth and having 1°p arameterization. The model is compiled in an a priori fashion entirely from existing geophysical literature, specifically, combining two regionalized crustal models with a high-resolution global sediment model and a global upper mantle model. The resulting WENA1.0 model consists of 24 layers: water, three sediment layers, upper, middle, and lower crust, uppermost mantle, and 16 additional upper mantle layers. Each of the layers is specified by its depth, compressional and shear velocity, density, and attenuation (quality factors, Q P and Q S ). The model is tested by comparing the model predictions with geophysical observations including: crustal thickness, surface wave group and phase velocities, upper mantle P n velocities, receiver functions, P-wave travel times, waveform characteristics, regional 1-D velocities, and Bouguer gravity. We find generally good agreement between WENA1.0 model predictions and empirical observations for a wide variety of independent data sets. We believe this model is representative of our current knowledge of crust and upper mantle structure in the WENA region and can successfully be used to model the propagation characteristics of regional seismic waveform data. The WENA1.0 model will continue to evolve as new data are incorporated into future validations and any new deficiencies in the model are identified. Eventually this a priori model will serve as the initial starting model for a multiple data set tomographic inversion for structure of the Eurasian continent.

Waveform Modeling of the Crust and Upper Mantle Using S, Sp, SsPmP, and Shear-Coupled PL Waves

“…The estimates of crustal thickness beneath these stations range between 36 km and 42 km (Figures 5a-d), comparable to regional estimates of 34 km to 40 km by Pasyanos et al (2004). We also note that the crust is slightly more thick in west Africa beneath seismic stations DBIC and MBO (~41-42 km) (Figures 5b and 5c), compared to the seismic stations TAM and MDT in north Africa (~36 km-38 km) (Figures 5a and 5d).…”

Crust and Lithospheric Structure - Global Crustal Structure

“…A major step forward was the publication of the global 2º Â 2º 3SMAC model (Nataf and Ricard, 1996) that for the first time permitted the calculation of crustal corrections to seismological and other geophysical observations. In the past decade, a tremendous amount of new seismic field observations have been made, thereby making it possible to improve the accuracy of previous global crustal models Pasyanos et al, 2004). In this chapter, we document these advances and summarize the current status of global crustal models.…”

The Prospect of Using Three-Dimensional Earth Models to Improve Nuclear Explosion Monitoring and Ground-motion Hazard Assessment

“…In nuclear explosion monitoring, for example, there is the possibility in the near term to use 3D earth models based on simple tectonic regionalization (e.g. Pasyanos et al, 2004;Johnson and Vincent, 2002) to develop travel time correction surfaces in regions where empirical ground-truth events are lacking such as in North Africa and large regions of the former Soviet Union (e.g. Flanagan et al, 2007).…”