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Improved Modeling and Prediction of Surface Wave Amplitudes

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[Technical Report, Final Report]

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We develop a membrane surface wave code named SurfMembrane for the purpose of predicting surface wave amplitudes in heterogeneous structures. The code models diffraction and scattering in heterogeneous structures and runs orders of magnitude faster than a corresponding 3D finite difference calculation. We compared the membrane calculations with a finite difference calculation for the same complex structure and found good agreement in amplitude variations. SurfMembrane also has the capability to calculate sensitivity kernels. We ran SurfMembrane for 73 earthquakes recorded on the US Array using the CMT solutions for those events to generate the source, and compared the calculations with data. We found that while the membrane calculations produced amplitude variations comparable to those observed, the detailed results are very sensitive to small errors in both the earth model and source radiation pattern. We inverted a large Eurasian data set for Q structure. The Eurasian data set retrieved from IRIS consisted of 59,000 waveforms from 1850 Eurasian and African earthquakes, all with CMT solutions. The data were subjected to an intensive quality control procedure to remove bad or questionable data, deep events and events with inaccurate CMT solutions. The final data set contained 23,148 waveforms from 998 events. There is a band of high attenuation stretching across the Middle East from the Mediterranean Sea to India. Together with this report, we are delivering SurfMembrane 3.0, together with test cases that can be run to ensure the program is working correctly. The program manual, which includes instructions for running the program and descriptions of all file formats, is given in the appendices to this report. We are also delivering the earth structures and derived attenuation coefficients from the Eurasian Q inversion study.

Subject Categories:

  • Physical and Dynamic Oceanography

Distribution Statement:

[A, Approved For Public Release]