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Updating Reverse Fault PFDHA Models and Distributions

Session: Fault Displacement Hazard: New Data and Modeling Advances I

Type: Oral

Date: 4/22/2021

Presentation Time: 10:45 AM Pacific

Description: 

The FDHI (fault displacement hazard initiative) working group has assembled an improved and expanded database of surface fault rupture measurements. This database has enabled our team to reevaluate the prior reverse fault PFDHA (probabilistic fault displacement hazard analysis) models and distributions and update as needed. The FDHI database increases the data that inform the statistics on the exceedance probability of principle displacement normalized by average (D/AD) and maximum displacement (D/MD). We find that the gamma distribution is still the best fit, but the increase in data has provided a more robust estimate of the distribution moments. We also confirm that on average there is asymmetry in the displacement along the length of a fault rupture (x/L) with the majority occurring near the center (x/L~0.5) and tapering towards the ends of the rupture (x/L~0). The new statistics are used to update the prior statistics using Bayesian conjugate priors. Other distributions for performing PFDHA for reverse faults, such as the probability of surface rupture given earthquake magnitude (SR | M), probability of exceedance of principle displacement given magnitude and surface rupture (D>D₀ | M,SR), probability of distributed displacement at a site given magnitude, surface rupture and closest distance from the principal rupture (d≠0|M,SR,R), and probability of exceedance of distributed displacement given magnitude, surface rupture and distance from the principal rupture (d>d₀ | M,SR,R), are informed by other databases along with the FDHI database. PFDHA calculations for reverse mechanisms, more so than for normal and strike-slip mechanisms, are sensitive to the probability of surface rupture given magnitude (SR | M). We are addressing this by using a statistical approach as well as a geometric approach to provide more than one method for assessing the hazard and quantifying the associated epistemic uncertainty.

Presenting Author: Robb E. S. Moss

Student Presenter: No

Authors