Lawrence Livermore National Laboratory



Introduction

The Geophysical Monitoring Programs (GMP) group at LLNL generates global-scale tomographic images of the Earth's interior for the advancement of seismic event monitoring capabilities. The project is funded by the Ground-based Nuclear Detonation Detection (GNDD) program within the National Nuclear Security Administration (NNSA). The most recently released Earth models (LLNL-G3D series) and supporting software (LLNL-Earth3D) are available for download on this webpage.

The LLNL-G3Dv3 Model

LLNL-G3Dv3 ( Simmons et al., 2012) is a global-scale model of the crust and mantle P-wave velocity with regional-scale details. The model is parametrized using a spherical tessellation with node spacing of ~1 degree in the upper mantle and ~2 degrees in the lower mantle. Although a spherical tessellation was used to define the latitude and longitude positioning of nodes, the model itself is aspherical with Earth’s ellipticity, mantle stretching, and undulating discontinuities in the crust and upper mantle built-in. In total, the model consists of 57 layers from the surface to the core and ~1.6 million nodes. 3-D ray tracing and a multi-scale imaging technique (PMTI, Simmons et al., 2011) were employed to create the image. The model was developed using over 2.8 million groomed and reprocessed P and Pn travel times with events located using the Bayesloc global multiple event location technique ( Myers et al., 2007, 2009, 2011). Original data sources include the EHB bulletin ( Engdahl et al., 1998) provided by the International Seismological Centre (ISC), the National Earthquake Information Center (NEIC) bulletin, a variety of regional bulletins. Arrival time measurements made by LLNL and other researchers augment bulletin data.  Waveform data sources used in this study include seismic deployments for Peaceful Nuclear Explosions (PNE’s), large refraction surveys, the USARRAY Transportable Array (TA), and temporary PASSCAL deployments around the world (IRIS).

Downloads

LLNL-G3Dv3_Vp_Model.zip P-wave model published in Simmons et al. (2012). (plain text files, 34 Mbytes) LLNL-MI-586552

LLNL-G3Dv3.e3d.binary P-wave model published in Simmons et al. (2012). (binary file version formatted for LLNL-Earth3D software, 85 Mbytes) LLNL-MI-586552

The LLNL-Earth3D Code for Extracting Model Parameters, Tracing Rays, and Computing Travel Times

LLNL-Earth3D is a java-based software package designed to support the use of the LLNL-G3D series of models. The primary purpose of the code is to compute 3-D ray paths for body waves and calculate travel times between a seismic source and a seismic station. The code navigates the hierarchical spherical tessellation framework of the LLNL-G3D models and is multi-threaded so that a number of ray paths and travel times can be computed concurrently. The current version of the Earth model (LLNL-G3Dv3) is based only on first arriving P-waves (P and Pn), but the code will attempt to compute travel times and 3-D ray paths for several secondary seismic phases which are currently being tested. Earth3D functionality includes outputting model parameters, such as seismic velocity and the depth (or radius) of velocity discontinuities. Output formats include Generic Mapping Tool (GMT) compatible ascii files, which can be used to create map projections of model parameters,1D and 2D velocity profiles, and profiles of the ray path from source to receiver.

Downloads

LLNL-Earth3D Java-based code package for 3-D ray tracing through the LLNL-G3D binary models. (.jar, 30 Mbytes) CODE-644272

LLNL-Earth3D-Manual User manual with examples. (.pdf) LLNL-SM-652345

Contacts

References

Simmons, N.A., S.C. Myers, G. Johannesson, and E. Matzel (2012). LLNL-G3Dv3: Global P-wave tomography model for improved regional and teleseismic travel time prediction, J. Geophys. Res., 117, doi:10.1029/2012JB009525.

Myers, S.C., G. Johannesson, and N.A. Simmons (2011). Global-scale P-wave tomography optimized for prediction of teleseismic and regional travel times for Middle East events: 1. Data set Development, J. Geophys. Res., 116, B04304, doi:10.1029/2010JB007967.

Simmons, N.A, S.C. Myers, and G. Johannesson (2011). Global-scale P-wave tomography optimized for prediction of teleseismic and regional travel times for Middle East events: 2. Tomographic inversion, J. Geophys. Res., 116, B04305, doi:10.1029/2010JB007969.

Simmons, N.A., A.M. Forte, L. Boschi, and S.P. Grand (2010). GyPSuM: A joint tomographic model of mantle density and seismic wave speeds, J. Geophys. Res., Vol. 115, B12310, doi:10.1029/2010JB007631.

Myers, S. C., G. Johannesson and W. Hanley (2009). Incorporation of probabilistic seismic phase labels into a Bayesian multiple-event seismic locator, Geophys. J. Int., 177 193-204, doi:10.1111/j.1365-246X.2008.04070.x

Myers, S. C., G. Johannesson and W. Hanley (2007). A Bayesian hierarchical method for multiple-event seismic location, Geophys. J. Int., doi:10.1111/j.1365-246X.2007.03555.x.


This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Web content release number LLNL-MI-652664.