What Happens When 250 Years of Rapid Ice Loss Induces One of the World's Fastest Crustal Uplift Rates Directly Above One of Its Fastest-Slipping Faults? Cryosphere-Solid Earth Interactions in the Glacier Bay Region, Southeast Alaska
Date: 4/25/2019
Time: 06:00 PM
Room: Grand Ballroom
The Glacier Bay region provides a unique opportunity to study cryosphere-solid earth interactions along a major strike-slip plate boundary. Since ~1770 AD, this region has lost >3000 km3 of ice, with ice thinning by >1 km in some places. The viscoelastic response to the integrated ice loss and the elastic response to present-day melting are together driving some of the fastest geodetic uplift rates on Earth today (>3 cm/yr). Through this fast-deforming region runs the right-lateral Fairweather Fault, which accommodates ~45 mm/yr of relative Pacific-North American plate motion and ruptured in multiple M>7.5 earthquakes in the 20th century. Using detailed ice models and a Maxwell viscoelastic structure [Hu et al., submitted] that together produce the best available fit to present-day GPS uplift rates, we find that the post-1770 ice loss and viscoelastic rebound likely imparted ~0.5-MPa shear and normal stress changes to the nearby Fairweather Fault, mostly in the 20th century. The location of maximum Coulomb stress increase coincides nearly exactly with the epicenter of the 1958 Mw~7.9 Fairweather Fault earthquake, the largest recent event in this region. The earthquake then propagated along (and only along) a section of fault that we find had been unclamped, with the highest slip directly underlying the Yakutat Icefield [Doser, 2010] and possibly enhanced by heavy post-1770 unclamping there. We find in 1D and full forward models that incorporating a transient rheology would have little effect on geodetic uplift rates or stress changes. We also bring in constraints from postseismic deformation following the 2013 Mw=7.5 Craig earthquake, which we find is well fit by lower crustal afterslip plus viscoelastic relaxation in the mantle. We are also using GRACE data to better constrain the ongoing elastic-viscoelastic mass changes, accounting for concomitant changes in sea level that result from these processes’ effect on the geoid and vice versa, and linking these processes more quantitatively to seismicity using moment balance considerations and seasonal fluctuations.
Presenting Author: Chris Rollins
Authors
Chris Rollins john.c.rollins@gmail.com Michigan State University, East Lansing, Michigan, United States Presenting Author
Corresponding Author
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Jeffrey T Freymueller freymuel@msu.edu Michigan State University, East Lansing, Michigan, United States |
Yan Hu yanhu11@ustc.edu.cn University of Science and Technology of China, Hefei, , China (Mainland) |
Jeanne Sauber-Rosenberg jeanne.m.sauber-rosenberg@nasa.gov NASA Goddard Space Flight Center, Greenbelt, Maryland, United States |
James Davis jdavis@ldeo.columbia.edu Lamont-Doherty Earth Observatory, Palisades, New York, United States |
What Happens When 250 Years of Rapid Ice Loss Induces One of the World's Fastest Crustal Uplift Rates Directly Above One of Its Fastest-Slipping Faults? Cryosphere-Solid Earth Interactions in the Glacier Bay Region, Southeast Alaska
Category
General Session