Simulation of Regional Explosion S-Phases (SIRES) Project

Conference · Thu Jul 15 04:00:00 EDT 2004

OSTI ID:15014532

Myers, S; Preston, L; Larsen, S; Smith, K; Wlater, W

Generation of S-waves from explosion sources continues to be an intriguing area of seismological research. Empirical studies document a general decrease in regional S-phase amplitudes (compared to P-phases) for explosions sources. Although decreased S-phase amplitude for explosive (compressional) sources is intuitive, a comprehensive physical understanding of the many mechanisms that contribute to S-phase excitation does not currently exist. Despite the success of many regional discriminant and magnitude methods that rely on decreased S-phase amplitude for explosion sources, instances remain where explosions produce anomalous S-phases amplitudes that confound regional methods. Scattering of the Rg phase is forwarded in several studies as an important mechanism for the generation of explosion S-waves. In this study we construct a 3-dimensional model of the Nevada Test Site (NTS) and the surrounding region. Extensive databases of geologic information, including existing 3-dimensional models developed under past and ongoing NTS programs, are used in the construction of a local model. The detailed local model is merged into a regional model that extends several hundred kilometers from the NTS. In addition to deterministic geologic structure and topography we introduce stochastic variability along geologic contacts and within geologic units. Model roughness made possible by the stochastic perturbations enhances scattering, allowing realistic simulation of the local and regional wavefield. In this phase of the project we report on version 1 of the NTS model and on preliminary validation tests. Validation simulations use e3d, a fully elastic, finite difference computer code. This code allows us to introduce 3D topographic effects, as well as 3D geologic variability. Simulations are compared to recordings of the 1993 NPE experiment. The validation data set consists of local and regional distance seismograms and provides a rigorous test of the distance and time evolution of the wavefield.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 15014532
• Report Number(s): UCRL-CONF-204629
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
COMPUTER CODES
EXPLOSIONS
GEOLOGIC STRUCTURES
NEVADA TEST SITE
S WAVES
SIMULATION
VALIDATION