SCEC Award Number 19222 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Development of Next-Generation PFDHA Using High-resolution Geodetic Imaging Data
Name Organization
Andrea Donnellan National Aeronautics and Space Administration Chris Milliner National Aeronautics and Space Administration Rui Chen California Department of Conservation
Other Participants Tim Dawson
Chris Madugo
James Dolan
SCEC Priorities 1a, 3d, 3e SCEC Groups Geodesy, EEII, Geology
Report Due Date 04/30/2020 Date Report Submitted 05/15/2020
Project Abstract
PFDHA is a probabilistic approach to characterize the hazard of distributed rupture that is used by engineers and hazard practitioners to safely design distributed infrastructure (e.g., gas and water pipelines, roads and bridges) that cannot avoid fault crossings. The primary limitation with the current PFDHA approach is that the probability models are constrained solely by field observations which are spatially sparse and have unknown uncertainties, which limit the model’s predictive power. Here our primary aim was to use pixel tracking techniques applied to satellite optical images to measure the magnitude, width and distribution of coseismic inelastic strain from recent surface ruptures to better constrain the probability of distributed fault rupture. Results from this project include, processing of satellite data to produce displacement maps of 9 earthquakes, modifying the PFDHA theory to incorporate the geodetic data, and generating geodetic-based fault displacement prediction equations to calculate fault displacement hazard maps. In addition, part of this work has led to an SRL publication (Milliner & Donnellan, 2020), helping understand the fracture distribution and timing during the Mw 7.1 2019 Ridgecrest earthquake sequence. Results derived from this project have been invaluable as they have helped secure a larger scale 3-year project funded by a NASA ROSES-ESI grant, to further advance the geodetic-based PFDHA approach. These next-generation geodetic-based PFDHA models will provide engineers with higher confidence on the likelihood of distributed rupture, and the data gathered here will help in validation of dynamic elastoplastic rupture simulations which could set the foundations towards a non-ergodic PFHDA approach.
Intellectual Merit The project addresses:
- What is the spatial distribution of inelastic strain? So far, most studies have provided scalar estimates of the amount of coseismic off-fault inelastic deformation. The across-fault spatial distribution has been captured in long-term geologic and geomorphic studies of faults and in specific instances along surface ruptures from offset man-made markers. Here we have attempted to define what functional form characterizes the spatial attenuation of inelastic strain with distance away from the rupture, which also allows us to create fault displacement prediction equations for PFDHA.
- What factors control off-fault deformation and distributed inelastic strain? What is the effect of fault compression and extension that is difficult to measure in the field? Here we used geodetic observations of the Ridgecrest earthquake rupture and created 2D strain maps to assess how the fault zone width and distribution of inelastic strain varied with varying amounts of fault zone compression and extension.
- Improving the PFDHA method which so far is constrained only by field-based data. We have developed an independent but complementary approach that uses high-resolution geodetic imaging data that can measure the spatial distribution of displacement across surface ruptures. Here we have developed new probabilistic theory and hazard equations.
- This project has also helped established new collaborations within SCEC including engineers at UCLA (Prof. Yousef Bozorgnia) who are developing a database of past earthquake ruptures, and hazard practitioners at consultancy firms at PG&E, LCI, and various state agencies (including Caltrans and CGS).
Broader Impacts • This project has led to training and professional development of a postdoc (C.M.).
• The research has led to increased collaboration between researchers at JPL and hazard practitioners at California Geological Survey at Sacramento and San Mateo.
• This work has important societal benefits as it will help create a better-informed design criteria for engineers to build more resilient infrastructure ultimately helping protect critical lifelines such as, road, bridges, and water, gas and telecommunication pipelines that are vulnerable to damage at fault crossings e.g., Elizabeth Lake near Palmdale and the I-5 at Cajon pass.
Exemplary Figure Figure 4