An analysis of core–mantle boundary related seismic waves using full-waveform modelling and adjoint methods
نویسندگان
چکیده
SUMMARY The core–mantle boundary (CMB) is the most abrupt internal discontinuity in Earth, marking solid–fluid between mantle and outer core that strongly affects dynamics of Earth’s interior. However, good agreement models CMB topographic variations still lacking. This probably due to difficulties relating observations on seismograms lack lowermost velocity structure. Using spectral-element synthetic adjoint methods, we perform traveltime analyses seismic waves interacting with CMB. We focus reflected refracted P S waves. select some important routinely used phases: ScS, SKS, SKKS, PcP, PKP, PKKP PcS, given their path through interaction These have been widely deployed by seismologists trying image topography To analyse reliability measuring traveltimes infer topography, experiments two ways. First, compute a dominant period T ≈ 11s, for computational efficiency, using existing topography. compare perturbations measured cross-correlation synthetics those predicted ray theory. find deviations from perfect theoretical predictions time shifts without Second, calculate Fréchet sensitivity kernels respect shear compressional wave speeds. also explicitly sensitivities interface. observe overall mostly volumetric structure imprints are less pronounced. Our study explains observed inferring provides suite finite frequency computed method. allow us qualitatively explain behaviour understand trade-off They can serve as reference effects phases. From our conclude that: i) anomalies Swaves more accord predictions, ii) ScS SKS phases pronounced iii) separating greater difficult, they intricately affect traveltime. propose jointly inverting full-waveform progress understanding deep Earth waveforms.
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ژورنال
عنوان ژورنال: Geophysical Journal International
سال: 2022
ISSN: ['1365-246X', '0956-540X']
DOI: https://doi.org/10.1093/gji/ggac389