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Seismic Imprints of a Hurricane Landfall: Deciphering the Atmosphere-Generated Signals From Large-Eddy Simulation of Turbulence

Description: 

One potential scenario of climate change is that tropical storms could become more intense, which will pose greater impacts upon their landfalls in coastal regions. The seismic ambient noise generated by these storms provides opportunities to study their imprints from a seismological view, and potentially facilitate the observation and understanding of their evolution.

We present a case study of Hurricane Isaac in 2012 which made landfall as Category 1 on the coast of Louisiana. This storm passed through the Transportable Array (TA) seismic stations on land, which had co-located seismometers and infrasound pressure sensors. One specific station TA.645A is right on the hurricane track and provides valuable in-situ surface pressure and seismic recordings within the hurricane. High-resolution wavelet spectrograms identify a clear calm hurricane eye. We demonstrate that within the period band ~ 20 - 100 s, seismic signals are directly contributed by turbulent surface pressure fluctuations through the local quasi-static coupling mechanism. The same turbulent pressure measurement can also be connected to surface wind reanalysis snapshots obtained from atmospheric studies.

We further perform numerical modeling of the seismic signals recorded inside the hurricane eyewall, where the strong azimuthal winds dominate. We use the open-source code Cloud Model 1 (CM1, Bryan & Fritsch, 2002) to perform a Large Eddy Simulation (LES) of turbulence within the hurricane boundary layer. This turbulent pressure field provides a realistic input for modeling seismic noise from the atmosphere, and we compute synthetic signals using quasi-static elastic Green’s functions. The modeled surface pressure and vertical displacement have similar amplitudes and coherence patterns to those observed in the real data. This lays the foundation for future work that combines in-situ seismic observations of hurricane landfall with atmospheric modeling to better constrain hurricane physics. It also demonstrates how seismic data can supplement the currently limited atmospheric datasets obtained by reconnaissance flights into hurricanes.

Session: ESC-SSA Joint Session: Climate Change and Environmental Seismology - I

Type: Oral

Date: 5/3/2024

Presentation Time: 02:15 PM (local time)

Presenting Author: Qing

Student Presenter: Yes

Invited Presentation: 

Authors