Natural Hazards Risk and Resiliency Research Center (NHR3)

Fault Displacement Hazard Initiative

Development of Empirical Database

The first step of the FDHI project is to update the existing databases with modern observations from recent earthquakes. The database will be developed as a structured relational database, populated with parameters based on input from the geoscience and modeling community. A relational database is ideal for compiling fault displacements because of the broad range of measurement types (e.g., horizontal throw vs. horizontal slip; on-fault vs. off-fault) in the published literature. As well, a relational database can easily accommodate new data types that may become available in future studies.

Analytical Modeling and Simulations

New or improved models using analytical (closed-form) solutions for tectonic deformation will be developed. Dynamic rupture simulations will be developed and validated for constraining scaling in empirical surface rupture models. Specific focus will be on secondary ruptures and distributed deformation. Current models are highly unconstrained due to small sample size of observations, limited magnitude range data, and incorporation of potentially incomplete datasets. Similar to what has been found for ground-motion PSHA, an important issue for PFDHA will be how the models extrapolate outside the range of data well constrained by the empirical rupture data sets. In particular, data sets for secondary fault rupture are very limited and extrapolation of the limited data can be constrained by numerical simulations.

Geotechnical Modeling of Site Effects on Surface Rupture

Parametric evaluations of geotechnical site conditions, such as material properties and thickness of unconsolidated sediments, will be used to develop constraints on site effects. Soil properties and geology have never been systematically addressed in past PFDHA efforts. Systematically quantifying how deformation relates to site conditions will produce more robust displacement estimates for discrete faults and deformation zones.

Evaluation of Statistical Methods

Empirical data sets of fault displacements typically suffer from unequal sampling (slip measurements) along the rupture length and biased over-sampling in areas of high slip. These issues should be addressed when developing empirical fault rupture models. Advanced statistical methods need to be developed and applied to address these features of fault rupture data sets such that the resulting empirical model is unbiased in estimating the fault rupture hazard in future earthquakes.

Development of Surface-Rupture Models for Primary and Secondary Ruptures

Next-generation models that account for not only magnitude, fault dip, and style-of-faulting, but also fault complexity and primary vs. secondary ruptures will be developed for engineering applications. This will include clear definitions of “primary” and “secondary” ruptures, and "on-fault" and "off-fault" deformation.

Implementation of Models for Engineering Applications

Trial applications of alternative models will be performed at selected sites that span the range of fault displacement hazard issues typically encountered (complex and distributed faulting, site-specific geotechnical characteristics), as well as types of infrastructure affected (e.g., bridges, dams, pipelines). This task also includes the development of written guidelines and recommendations for the use of the models in engineering applications.