Stress Promotion of the 1958 M_w∼7.8 Fairweather Fault Earthquake and Others in Southeast Alaska by Glacial Isostatic Adjustment and Inter‐earthquake Stress Transfer

Abstract

Introduction 1.1. Background and Motivation Southeast Alaska provides a unique opportunity to study the influence of glacial isostatic adjustment (GIA) on fault stress and earthquake activity. Since ca. 1770 AD, the Glacier Bay Icefield alone has lost >3,000 km 3 of ice, with ice thinning up to 1.5 km (Figure 1a, grayscale squares). Deglaciation began throughout the rest of southeast Alaska ca. 1900 and accelerated toward the end of the 20th century (Larsen et al., 2004, 2005). This past ice loss induces a prolonged viscoelastic response in the solid earth, while continuing ice loss induces an (effectively instantaneous) elastic response. In southeast Alaska, these two responses combine to produce present-day surface uplift rates of up to ∼4 cm/yr, among the fastest on Earth, coupled with several mm/yr of horizontal motion (

CitcomSVE: A Three‐Dimensional Finite Element Software Package for Modeling Planetary Mantle’s Viscoelastic Deformation in Response to Surface and Tidal Loads

“…The deviatoric stress $${\tau }_{ij}$$ is used as the pre‐stress for calculations for the next time step. $${\tau }_{ij}$$ is also used for other geophysical applications including stress‐dependent viscosity modeling (Bellas & Zhong, 2021; Kang et al., 2022; Zhong & Watts, 2013) and GIA induced seismicity (e.g., Rollins et al., 2021). In fact, the total stress $${\sigma }_{ij}$$ is never computed in CitcomSVE.…”

Climate- and Weather-Driven Solid-Earth Deformation and Seismicity

“…This combined glacial unloading effect can influence seismicity in volcanic (e.g. Sigmundsson et al, 2010), and tectonic dip-slip and strike-slip settings (Sauber et al, 2000(Sauber et al, , 2021Rollins et al, 2021). Rollins et al (2021) illustrate the viscoelastic stress changes associated with a scenario of 1 m/yr glacial unloading over 200 years, alongside a vertical strike-slip fault.…”

“…Similarly, Sauber and Ruppert (2008) suggest that the rapid ice wastage between 2002 and 2006 in the Icy Bay may have affected seismicity rates in the area. At longer timescales, Rollins et al (2021) show that rapid GIA following the thinning of the Bay Icefield since 1770, and elsewhere in southeast Alaska since 1900, likely promoted Coulomb stress at the location of the 1958 Mw 7.8 Fairweather Fault earthquake and of at least 23 of 30 known Mw≥5.0 earthquakes in southeast Alaska (Figure 8B).…”

“…Sigmundsson et al, 2010), and tectonic dip-slip and strike-slip settings (Sauber et al, 2000(Sauber et al, , 2021Rollins et al, 2021). Rollins et al (2021) illustrate the viscoelastic stress changes associated with a scenario of 1 m/yr glacial unloading over 200 years, alongside a vertical strike-slip fault. Rapid GIA acts to unclamp the fault, promoting fault failure, and the Coulomb stress (Figure 4) amplitude reaches 0.5 MPa with an asymmetrical distribution caused by the unloading location with respect to the fault (Figure 8A).…”

Climate change and seismic resilience: Key considerations for Alaska’s infrastructure and built environment

“…For instance, the melting of glaciers can lead to changes in the stress distribution along major faults throughout Alaska, potentially increasing the frequency and magnitude of earthquakes. Rollins et al [ 12 ] discussed the impact of glacial melt on the 1958 moment magnitude, M w , 7.8 earthquake in Alaska, which triggered a landslide in Lituya Bay, resulting in a tsunami with a record-breaking maximum wave height of 1720 meters. Furthermore, the authors found that 23 of the 30 instrumentally constrained M w ≥5.0 earthquakes in Southeast Alaska were promoted by glacial isostatic adjustment.…”