Sea Level Rise Effects on Earthquake-induced Soil Liquefaction
Description:
Global sea levels are expected to increase up to five meters by the year 2150. Higher marine water levels as well as ocean fluctuations will also raise unconfined coastal groundwater levels. These fluctuations pose multiple interrelated coastal hazards. Currently, there has been minimal attention paid to the effects of sea level rise on groundwater, specifically how rising groundwater levels interact with hazards such as earthquake-induced soil liquefaction. We propose to use a probabilistic liquefaction hazard assessment (PLHA) to obtain annual rates of nonexceedance of factor of safety of liquefaction. Our approach integrates the liquefaction uncertainty into the hazard calculation by performing a PLHA for every event in the PSHA. Existing codes for performing PLHA are decoupled as first a probabilistic seismic hazard analysis (PSHA) is required to obtain a hazard curve. Drawbacks of this method are it only accounts for the influence of magnitude on liquefaction because it uses a small number of magnitudes and selection of the magnitudes requires judgment. We adopt the UCERF3 source model, which uses over a million events. For each event, ground motion at the site is a random variable that is used to compute cyclic stress ratio (CSR). Cyclic resistance ratio (CRR) is also a random variable obtained from a liquefaction triggering model. Because CSR and CRR are log normally distributed, we can use a closed-form solution to obtain a distribution for factor of safety (FoS). The rate of the event is then multiplied by the cumulative distribution function (CDF) of FoS and the rate-weighted CDF’s are summed over all events to compute the liquefaction hazard curve. Using efficient vectorized operations, the PLHA runs within seconds for a single site despite the large number of calculations. The code is used to compute the PLHA for an example soil profile at Cardiff State Beach in Southern California for current groundwater conditions and for a 1-meter sea level rise scenario.
Session: Earthquake-triggered Ground Failure: Data, Hazards, Impacts and Models - I
Type: Oral
Date: 4/17/2025
Presentation Time: 08:15 AM (local time)
Presenting Author: Meera
Student Presenter: Yes
Invited Presentation:
Poster Number:
Authors
Meera Kota Presenting Author Corresponding Author meerakota@g.ucla.edu University of California, Los Angeles |
Scott Brandenberg sjbrandenberg@g.ucla.edu University of California, Los Angeles |
Margit Maple margitmaple@gmail.com University of California, Los Angeles |
Timu Gallien tgallien@seas.ucla.edu University of California, Los Angeles |
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Sea Level Rise Effects on Earthquake-induced Soil Liquefaction
Session
Earthquake-triggered Ground Failure: Data, Hazards, Impacts and Models