Controls on surface wave overtone interference
| العنوان: | Controls on surface wave overtone interference |
|---|---|
| المؤلفون: | Jordyn C. Babikoff, A. Hariharan, Göran Ekström, Colleen A. Dalton |
| المصدر: | Geophysical Journal International. 228:1665-1683 |
| بيانات النشر: | Oxford University Press (OUP), 2021. |
| سنة النشر: | 2021 |
| مصطلحات موضوعية: | Geophysics, Optics, Geochemistry and Petrology, Surface wave, business.industry, Overtone, Astrophysics::Solar and Stellar Astrophysics, Interference (wave propagation), business, Geology |
| الوصف: | SUMMARY Measurements of fundamental-mode (FM) surface waves along the minor arc are impacted by overtone interference. This interference is primarily due to major-arc overtones for Rayleigh waves and minor-arc overtones for Love waves. In both cases, interference contaminates measurements of phase and amplitude and can introduce bias in seismic images. Here, we use synthetic seismograms computed via normal mode summation to probe how interference can vary as a function of the surface wave group velocities, source mechanism and depth, which control the relative excitation of the FM and overtones, and period. By comparing seismograms that include all overtones to those that include only the FM, we can quantify the interference, i.e., how the presence of the overtones perturbs the FM phase and amplitude. We compare the strength of this interference to calculations of excitation of the overtones and FM. We show that these calculations explain well the varying strength of interference for different source mechanisms and depths. Notably, these calculations illuminate source depths where Love wave overtone excitation is quite low and therefore interference is unusually weak, and depths where Rayleigh wave FM excitation is low and therefore interference is unusually strong. Our analysis also reinforces the dependence of the interference on the FM and overtone group velocities. For Love waves, this results in weak minor-arc overtone interference at long periods and, for continental paths, short periods. For Rayleigh waves, the differing overtone and FM group velocities and the relative excitation of the overtones and FM explain rapid variations in the strength of Rayleigh wave major-arc overtone interference as a function of epicentral distance. We then show that real data are affected by the relative excitation of the FM and overtones. We find that errors in Rayleigh wave phase velocities determined at the EarthScope USArray stations are larger when the ratios of overtone to FM excitation are larger. We also find a dependence of phase velocity error on excitation ratio for Love waves, and we identify the presence of major-arc overtone interference in Love wave measurements. Our results highlight opportunities for more nuanced quality control of surface wave measurements. The relative excitation ratio of the overtones and FM may be a better criterion for event selection than source depth, allowing deeper events that well excite FMs to be included and shallower events with large overtone excitation to be excluded. This would allow the collection of more accurate measurements that will increase the precision of seismic images. |
| تدمد: | 1365-246X 0956-540X |
| الوصول الحر: | https://explore.openaire.eu/search/publication?articleId=doi_________::fe2a8925a9d83c954f69dde690f27930Test https://doi.org/10.1093/gji/ggab424Test |
| حقوق: | OPEN |
| رقم الانضمام: | edsair.doi...........fe2a8925a9d83c954f69dde690f27930 |
| قاعدة البيانات: | OpenAIRE |
| تدمد: | 1365246X 0956540X |
|---|