Olinger Seth D.

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Olinger
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Seth D.
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  • Article
    Tidal and thermal stresses drive seismicity along a major Ross Ice Shelf rift
    (American Geophysical Union, 2019-05-23) Olinger, Seth D. ; Lipovsky, Bradley P. ; Wiens, Douglas A. ; Aster, Richard C. ; Bromirski, Peter D. ; Chen, Zhao ; Gerstoft, Peter ; Nyblade, Andrew A. ; Stephen, Ralph A.
    Understanding deformation in ice shelves is necessary to evaluate the response of ice shelves to thinning. We study microseismicity associated with ice shelf deformation using nine broadband seismographs deployed near a rift on the Ross Ice Shelf. From December 2014 to November 2016, we detect 5,948 icequakes generated by rift deformation. Locations were determined for 2,515 events using a least squares grid‐search and double‐difference algorithms. Ocean swell, infragravity waves, and a significant tsunami arrival do not affect seismicity. Instead, seismicity correlates with tidal phase on diurnal time scales and inversely correlates with air temperature on multiday and seasonal time scales. Spatial variability in tidal elevation tilts the ice shelf, and seismicity is concentrated while the shelf slopes downward toward the ice front. During especially cold periods, thermal stress and embrittlement enhance fracture along the rift. We propose that thermal stress and tidally driven gravitational stress produce rift seismicity with peak activity in the winter.
  • Article
    Ross ice shelf icequakes associated with ocean gravity wave activity
    (American Geophysical Union, 2019-08-01) Chen, Zhao ; Bromirski, Peter D. ; Gerstoft, Peter ; Stephen, Ralph A. ; Lee, Won Sang ; Yun, Sukyoung ; Olinger, Seth D. ; Aster, Richard C. ; Wiens, Douglas A. ; Nyblade, Andrew A.
    Gravity waves impacting ice shelves illicit a suite of responses that can affect ice shelf integrity. Broadband seismometers deployed on the Ross Ice Shelf, complemented by a near‐icefront seafloor hydrophone, establish the association of strong icequake activity with ocean gravity wave amplitudes (AG) below 0.04 Hz. The Ross Ice Shelf‐front seismic vertical displacement amplitudes (ASV) are well correlated with AG, allowing estimating the frequency‐dependent transfer function from gravity wave amplitude to icefront vertical displacement amplitude (TGSV(f)). TGSV(f) is 0.6–0.7 at 0.001–0.01 Hz but decreases rapidly at higher frequencies. Seismicity of strong icequakes exhibits spatial and seasonal associations with different gravity wave frequency bands, with the strongest icequakes observed at the icefront primarily during the austral summer when sea ice is minimal and swell impacts are strongest.