The Displacement Approach to Probabilistic Fault Displacement Hazard Analysis; Issues and an Example
Session: Fault Displacement Hazard: New Data and Modeling Advances II
Type: Oral
Date: 4/23/2021
Presentation Time: 09:45 AM Pacific
Description:
Most publications and current application of probabilistic fault displacement hazard analysis (PFDHA) are focused on the earthquake approach, whereby hazard at a site is calculated from a “traditional” fault source model (that produces the magnitude-recurrence-location distribution of earthquakes on a fault source) and one or more fault displacement models (consisting of conditional probabilities of rupture at a site and displacement exceedance equations). This is appropriate when studies lack detailed site-specific information on the timing and amount of past displacements. For cases where paleoseismic information is available, the displacement approach to PFDHA is recommended. The displacement approach relies on geologic information to estimate mean slip per event and recurrence rate directly, as opposed to estimating these parameters from an arbitrary or general fault source model. By incorporating site-specific paleoseismic data, the displacement approach has smaller aleatory variability compared to the earthquake approach leading to steeper hazard curves that result in more stable design displacement values. However, proper implementation of the displacement approach requires a clear methodology for capturing model epistemic uncertainty given the often-limited number of interpreted paleoseismic events available and the uncertainties in those interpreted events. We build on a displacement approach developed by Abrahamson that accounts for a small number of past displacement estimates using a maximum-likelihood approach that adjusts the mean site-specific displacement based on the number of observations and an average displacement “prior” calculated using earthquake approach fault displacement models. We show an example of its implementation that includes logic trees to capture uncertainties in interpretations of paleoseismic displacement-per-event and event timing.
Presenting Author: Stephen C. Thompson
Student Presenter: No
Authors
Stephen Thompson Presenting Author Corresponding Author thompson@lettisci.com Lettis Consultants International, Inc. |
Arash Zandieh zandieh@lettisci.com Lettis Consultants International, Inc. |
Norman Abrahamson abrahamson@berkeley.edu University of California, Berkeley |
Nora Lewandowski lewandowski@lettisci.com Lettis Consultants International, Inc. |
John Baldwin baldwin@lettisci.com Lettis Consultants International, Inc. |
Brian Gray bgray@lettisci.com Lettis Consultants International, Inc. |
Ray Weldon ray@uoregon.edu University of Oregon |
William Lettis lettis@lettisci.com Lettis Consultants International, Inc. |
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The Displacement Approach to Probabilistic Fault Displacement Hazard Analysis; Issues and an Example
Category
Fault Displacement Hazard: New Data and Modeling Advances