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Séminaire ISTerre
Oceanic Sources of Seismic Body Waves at the Global Scale: Modeling and Applications.
jeudi 24 octobre 2024 - 11h00
Lisa Tomasetto - PhD Student ISTerre---
Seismic waves traveling through the Earth’s interior represent a main observable constraining the inner Earth’s physical properties, allowing Earth scientists to formulate hypotheses on the processes that govern our planet. However, major Earthquakes occur in redundant areas such as plate boundaries, and broadband seismic stations are heterogeneously distributed on continents, leading to an unevenly illuminated Earth. This limitation affects our ability to capture a global view of Earth's interior Beyond earthquakes, interactions between oceanic waves and the seafloor also generate seismic waves recorded globally and referred to as natural ambient “noise”. In particular, the 3-10s period band, known as the secondary microseismic band, corresponds to non-linear oceanic wave-wave interaction and represents the highest peak in energy in a seismic station PSD. While surface waves are prominent in this band, body waves, which sample deeper areas and are less scattered, can also be identified. These body waves are valuable for examining the properties of the deep Earth due to their sensitivity to the inner medium. Recent improvements in global oceanographic hindcast, such as the WAVEWATCHIII model, have allowed seismologists to track the spatiotemporal behavior of these ocean-generated seismic sources. Since these unconventional sources are non-impulsive, interferometry methods correlating signals between stations for a few hours are necessary to highlight body waves at the global scale. In this two-part talk, I will first introduce the WMSAN Python library, for Wave Model Sources of Ambient Noise, which allows for the visualization of ambient noise sources maps and computation of proxy for seismic observables in a user-friendly fashion. Then I will show an application to travel-time measurements evolution of mantle-sensitive interference (PP-P) for a major oceanic event in the Northern Atlantic from 9-11 December 2014. Confronting our travel times measurements to global 3D model counterparts, we show that such methodology could add measures to traditional earthquake travel times datasets with different coverage.
Equipe organisatrice : Ondes et structures
Amphithéâtre Killian, Maison des Géosciences, 38400 Saint Martin d'Hères