Enhancing the Observability of Precritical PKiKP Phases with Polarization Filters and Incoherent Array Processing
Description:
The inner core plays a key role in Earth’s dynamo, which generates and maintains the magnetic field throughout Earth’s history. Seismically observable properties of the inner core, such as the impedance change and topography at the inner core boundary, provide insight into its composition and evolution. In this study, we focus on documenting and enhancing the observability of steep angle reflections (PKiKP) from the inner core boundary (ICB). At precritical distances (< ~90 degrees), PKiKP waves are uniquely sensitive to the change in density and shear wave velocity across the ICB. The coda waves following precritical PKiKP are sensitive to scatterers and other complex structure within the inner core. PKiKP has very small amplitude at precritical distances and has mostly been observed at high frequencies (1–3 Hz) using small-to-medium aperture arrays (< 50–100 km) of short-period seismometers. Occasionally, PKiKP has been observed at individual three-component broadband stations. Here we search for precritical PKiKP waves recorded at broadband seismometers deployed across North America from earthquakes in Central America. We examine how its frequency-dependent amplitude varies with focal mechanism, background noise level, and local site conditions. We experiment with frequency dependent polarization filters and incoherent array processing as means of enhancing the observability of PKiKP and its coda waves. Polarization filters can extract clear seismic phases which are strongly polarized relative to the noise, for instance by comparing horizontally rectilinear motion (HRM) and vertically rectilinear motion (VRM). This approach has recently been used to detect a solid inner core on Mars with data from a single seismometer.
Session: Earth’s Structure from the Crust to the Core [Poster]
Type: Poster
Date: 4/16/2025
Presentation Time: 08:00 AM (local time)
Presenting Author: Jiaqi
Student Presenter: Yes
Invited Presentation:
Poster Number: 94
Authors
Jiaqi Geng Presenting Author Corresponding Author jiaqi.geng@utah.edu University of Utah |
Keith Koper keith.koper@utah.edu University of Utah |
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Enhancing the Observability of Precritical PKiKP Phases with Polarization Filters and Incoherent Array Processing
Category
Earth’s Structure from the Crust to the Core