Geotechnical lessons from the M_w 7.1 2018 Anchorage Alaska earthquake

Abstract

The 2018 Mw 7.1 Anchorage, Alaska, earthquake is one of the largest earthquakes to strike near a major US city since the 1994 Northridge earthquake. The significance of this event motivated reconnaissance efforts to thoroughly document damage to the built environment. This article presents the spatial variability of ground motion intensity and its correlation with subsurface conditions in Anchorage, the identification of liquefaction triggering in the absence of surficial manifestations (such as sand boils or sediment ejecta), cyclic softening failure in organic soils, and the poor performance of anthropogenic fills subjected to cyclic loading. In addition to lessons from observed ground deformation and geotechnical effects on structures, this article provides case studies documenting the satisfactory behavior of improved ground subjected to cyclic loading and the appropriateness of current design procedures for the estimation of seismically induced sliding displacements of mechanically stabilized earth walls.

National liquefaction loss database and event-level fragility functions

“…After the loss data for this study were collected and finalized, additional information has been publicly released regarding liquefaction losses in the 2018 Anchorage and the 2019 Ridgecrest events (Cabas et al, 2021; Zimmaro et al, 2020). These details increase liquefaction loss values in historical events and would therefore increase estimates of loss in section “Correlations between liquefaction costs and LHMs.” In some cases, it would also slightly increase theoretical probabilities of exceeding DSs in sections “Cost-based fragility function plots” and “Relative damage-based fragility function results.”…”

“…After the loss data for this study were collected and finalized, additional information has been publicly released regarding liquefaction losses in the 2018 Anchorage and the 2019 Ridgecrest events (Cabas et al, 2021;Zimmaro et al, 2020). These details increase liquefaction loss values in historical events and would therefore increase estimates of loss in section ''Correlations between liquefaction costs and LHMs.''…”

Acoustic emission induced by sand liquefaction during vibration loading

“…The issue of the time of liquefaction triggering 8 was studied in the frequency domain while the frequency content of a ground motion changes rapidly upon triggering of liquefaction: namely, high-frequency components are weakened and low-frequency components are amplified upon triggering. The phenomenon was explained due to the changes in soil stiffness that is different before and after the triggering of liquefaction when the soil behaves almost like a liquid 8 , 12 . Such an accelerogram-based approach was shown to be a promising tool for liquefaction occurrence 12 – 18 .…”

“…The phenomenon was explained due to the changes in soil stiffness that is different before and after the triggering of liquefaction when the soil behaves almost like a liquid 8 , 12 . Such an accelerogram-based approach was shown to be a promising tool for liquefaction occurrence 12 – 18 .…”