A Simple, Causal Method to Incorporate Anelastic Attenuation into Finite-Difference Calculations.
Abstract
Current nuclear treaty monitoring interest has shifted to the verification of a comprehensive test ban treaty (CTBT), including the detection of the first test of potential proliferators. Predictive modeling capabilities are crucial, not just desirable, in the context of CTBT and proliferation monitoring. Synthetic seismograms generated with the linear-finite-difference (LFD) code are particularly useful for regions where earthquake or explosion data are not available. However, to date many LFD modeling exercises are still limited to the elastic case only. This report describes a simple approach to include inelastic attenuation in the LFD calculations. The algorithm gives a damping effect equivalent to what would be obtained by solving the viscoelastic wave equation. Testings of this algorithm with planar P, Rg, and Lg waves demonstrate that this method generates a frequency-independent damping over a rather broad band, which is equivalent to a Q increasing linearly with frequency. Any Q model that has a form other than Q = Qo f1 can be simulated easily by superposing LFD results generated at several separate LFD runs corresponding to sampled Q-f pairs of the desired Q structure. One shortcoming is that the performance of this attenuation operator degrades slightly at very low frequencies. Nevertheless, the shortcomings of this algorithm are outweighed by the simplicity. Most importantly, this procedure preserves the causality.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 21, 1995
- Accession Number
- ADA310750
Entities
People
- Rong-song Jih
Organizations
- Phillips Laboratory