Location of Seismic “Hum” Sources Following Storms in the North Pacific Ocean

TitleLocation of Seismic “Hum” Sources Following Storms in the North Pacific Ocean
Publication TypeJournal Article
Year of Publication2019
AuthorsMaurya, S, Taira, T'aki, Romanowicz, B
JournalGeochemistry, Geophysics, Geosystems
Type of ArticleJournal Article

We investigate the spatially and temporally varying distributions of sources of the Earth's low-frequency seismic hum at high space-time resolution during a seismically quiet 7-day period in December 2015, when two large storms with different reaches propagate across the North Pacific Ocean. We integrate information from a variety of data from ocean wave height, infragravity wave prediction model, and broadband seismic data. We analyze seismic data to understand the seismic hum better: power spectral density at stations for detection and location of sources using array beamforming and backprojection methods, with a ~3-hr temporal and ~5° spatial resolution. For storms propagating west to east across the northern Pacific hitting the west coast of North America broadscale, we show that the distribution of hum sources is consistent with a model of seismic energy generated via infragravity waves, produced near the impact location of the storm, and propagating along the coast as well as toward the open ocean. The generation of seismic hum depends strongly on the reach of the storm and is very weak for a storm with more northerly propagation toward Alaska. At shorter periods (e.g., ~70 s), the seismic hum is generated in a narrow band that follows the coast, reaching progressively further to the north, while at longer periods (e.g. 150 s), it covers a broader area reaching far into the deep ocean. It may thus be possible to predict the distribution of the strongest “hum” sources, to first order, from the knowledge of the direction of propagation and strength of northern Pacific storms.


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