Detection of Teleseismic P‐waves in the Correlation Wavefield from Significant Secondary Microseism Events
Date:
Boue, P.* and Tomasetto, L., “Detection of Teleseismic P‐waves in the Correlation Wavefield from Significant Secondary Microseism Events”, vol. 2021, Art. no. S35A‐10, 2021.
Abstract
When computed from continuous seismic recording (a.k.a. ambient noise) in the 3 to 10-second period band, the Earths correlation wavefield is dominated by surface waves, but it also shows prominent P-waves teleseismic phases. It has already been shown that these body waves signals, which travel through the mantle and core, carry valuable information about the deep Earth structures and could be used as a complement to earthquake data. Such a microseism-based dataset is sensitive to the deep structure between pairs of seismic receivers. Hence, an opportune selection of these station pairs could fill in the inherent lack of illumination produced by uneven source-receiver geometries. For a given station pair, only very specific microseism-events contribute to the illumination of a specific target, such as a midpoint reflector at the CMB between the two sensors. In this study, we investigate the possibility to measure P-wave teleseismic phases from specific source-receiver-receiver combinations. First a catalog of major microseism events (including timing, location and pressure field) is built from a secondary microseism model derived from oceanic global sea-state hindcast. Knowing the source location, receiver pairs are then selected based on specific interferometric patterns (PP-P, PKPPcP-PKP, …). Compared to the classical ambient-noise correlation approach, which relies on stacking months of daily correlations, this workflow allows us to observe teleseismic P wave signal propagating between pairs of receivers from a much shorter observation time-window (typically one or two days). In addition, the knowledge of the source location and timing allows to bypass the classical assumption of a sufficient convergence of the correlation functions toward the Greens function without compromising our constraint on the structural sensitivity.