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Ambient Seismicity on Europan Analogs using the Seismometer to Investigate Ice and Ocean Structure (SIIOS)
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  • Angela Marusiak,
  • Daniella DellaGiustina,
  • S. Hop Bailey,
  • Veronica Bray,
  • Brad Avenson,
  • Erin Pettit,
  • Renee Weber,
  • Nicholas Schmerr,
  • Natalie Wagner
Angela Marusiak
University of Maryland

Corresponding Author:[email protected]

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Daniella DellaGiustina
University of Arizona
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S. Hop Bailey
University of Arizona
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Veronica Bray
University of Arizona,Imperial College London
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Brad Avenson
Silicon Audio
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Erin Pettit
Oregon State University
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Renee Weber
NASA Marshall Space Flight Center
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Nicholas Schmerr
University of Maryland at College Park
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Natalie Wagner
University of Alaska Fairbaks
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Abstract

The Seismometer to Investigate Ice and Ocean Structure (SIIOS) project is exploring the science capabilities of seismometers in ocean world analog environments. Ocean worlds, such as Europa, Enceladus and Titan, have thick global icy shells overlying liquid oceans. The icy shells may be seismically active due to tidal stresses. SIIOS tests several seismometers in a small-aperture array in a mock-lander configuration to quantify the ability to detect, locate, and identify seismic sources, as well as constrain local ice structure. The SIIOS experiment was deployed on two terrestrial analogs for ocean worlds. We first deployed on Gulkana Glacier in Alaska in September 2017, and then deployed in Northwestern Greenland, over a subglacial lake from May 2018-August 2018. Both areas serve as analog locations for Europa due to the layering of ice, water and rock. Gulkana was a relatively noisy site due to surface runoff and drainage, higher topographic variation (inducing rockfalls), and proximity to active plate boundaries. Greenland was a quieter site, in part due to its geologic setting high on the ice sheet, as well as from the installation process. During the Greenland deployment, we covered instruments with a large aluminum box that was buried, thus reducing noise from atmospheric and thermal effects. At both analog sites, the instruments passively recorded seismicity and seismic background noise. The passive data was used to create power spectral density (PSDs) and then probability density functions (PDFs), of the background noise. The PDFs of Gulkana showed higher noise levels compared to those of Greenland. Using the passive data, we detected and identified events originating from ice quakes, and in the case of Gulkana; rockfalls and drainage from a nearby moulin. A frequency-dependent polarization analysis was also conducted to indicate the dominant directionality of the background signals through time. The results indicate how background or ambient signals could be used on ocean worlds to characterize the local seismicity.