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Revisiting Earth’s Inner Core: Historical Data Using Modern Approaches

Description: 

Careful analysis of what, at the time, were considered high-quality compressional phase data led Inge Lehmann to interpret the existence of a solid inner core in 1936. Greater understanding of the physical properties of the inner core came through normal mode observations studied by Adam Dziewonski and Freeman Gilbert in 1971. What makes the discovery of the inner core by Inge Lehmann even more remarkable was that it was done by way of analog records before any idea of broadband seismology or digital data existed. Along with identifying the existence of the inner core she was also able to estimate the radius of the inner core to be 1405 km (more modern models, such as ak135 estimate the inner core to be 1218 km).

To identify potential limitations produced by phase identification on historical instruments, which had less accurate timing and potentially higher noise than modern broadband instruments, we compare International Seismological Centre (ISC) archived phase arrivals between 1906 and 1935 to those obtained on modern broadband data. We also revisit Inge Lehmann’s observations from a modern perspective by estimating uncertainties in the phase arrival information of the core triplication phases PKPdf, PKPab, and PKPbc. We then look at how these uncertainties propagate into uncertainty in the radius of the inner core by comparing these phase arrivals to those predicted by ray tracing using perturbations of the inner core radius of ak135.

Session: Legacy Seismic Data Collections: The Present State of and Future Outlook for Data from the Past [Poster]

Type: Poster

Date: 4/18/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Adam Ringler

Student Presenter: No

Invited Presentation: 

Authors