Role of Spatial Variability in Liquefaction Consequence Severity

Oregon State University, Corvallis OR

Investigators

Abstract

Earthquake-induced liquefaction can occur when strong ground shaking causes saturated, loose sand and silt sediments to lose their strength and ability to support structures, such as buildings, bridges, and port and harbor infrastructure. Unfortunately, population centers are often founded above and within the kinds of sediments that are susceptible to soil liquefaction. The periodic earthquakes produced in seismically-active zones tend to lead to widespread damage that can affect housing, critical infrastructure, utility, and emergency service networks. For example, $15B of damage was attributed to soil liquefaction resulting from the 2010-11 Canterbury Earthquake Sequence in New Zealand. More than 25,000 homes experienced liquefaction-related damage in the Tohoku and Kanto districts in Japan. The breadth of damage and disruption to the residents of earthquake-prone areas pose significant economic consequences if the liquefaction hazard is not sufficiently explored and mitigated, impacting the ability of communities to recover from an earthquake event. This project aims to leverage the significant dataset gathered within the New Zealand Geotechnical Database (NZGD) to identify the role of spatial variability of liquefaction-susceptible soil deposits on the severity of liquefaction-induced consequences. An improved understanding of the liquefaction phenomenon and resulting consequences may be obtained by linking those detectable geomorphological signatures to the performance of existing liquefaction triggering and severity models and the actual responses observed during the 2010-11 Canterbury Earthquake Sequence. Sites identified in the NZGD that have a sufficient number of soil explorations to establish the vertical and horizontal inherent variability of liquefiable soil deposits will form the basis for this work. One doctoral student and one undergraduate research assistant will work on this project, under the supervision of the Principal Investigator and in collaboration with researchers from the University of Canterbury, New Zealand. The analytical procedures necessary for evaluating the inherent spatial variability of soils will be distilled into a broadly-, and freely-distributed user-friendly framework to spur greater application of random field methods to the evaluation of liquefiable soil sites. This study will address potential shortcomings in existing techniques to assess liquefaction severity by considering the geologic and geomorphological signature of potentially-liquefiable soils deduced from measures of soil spatial variability quantified using random field theory (RFT). Observations of post-earthquake liquefaction severity following the Canterbury Earthquake Sequence provide a ready source of observations by which to test whether or not knowledge of spatial variability can reduce the inaccuracy of liquefaction severity measures. Measures of soil autocorrelation and inherent variability will be directly quantified using cone penetration test data in the NZGD using rigorous statistical methods to improve our understanding of the range in vertical and horizontal measures of spatial variability of liquefaction susceptible soils. Furthermore, this work will evaluate the potential for correlation of quantified random field model parameters and geomorphologic controls to relative accuracy or inaccuracy in liquefaction severity measures. This work will lay the groundwork for future studies by significantly increasing the number of sites characterized within the RFT framework, particularly measures of horizontal variability, as well as train current and future earthquake engineering educators and students in RFT to promote awareness of this interpretational framework by teaming with the NSF-sponsored Geotechnical Extreme Events Reconnaissance Association. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.