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PERFORMANCE BASED STATEMENT OF WORK

1.0 INTRODUCTION AND BACKGROUND

The National Seismic Hazard Model will be updated in 2023. This will entail revisions to a variety of its components, including the earthquake rate model, seismicity rate model, and fault rupture probabilities. A key ingredient of the earthquake rate model is a set of fault slip rates and their uncertainties. These rates have been traditionally estimated using geologic fault slip rates, with minimal input from slip rates derived from the geodetically-measured interseismic crustal motions. The existence of well-vetted geodetic datasets of interseismic deformation rates

(principally GPS velocities) and derived products, as well as the maturing of several interpretational models over the past decade, prompts a renewed effort to incorporate geodesy into the NSHM. The Tectonic Geodesy Working Group of the current NSHM requires advanced geophysical models to guide the development of deformation models that will contribute to the earthquake rate model.

Geodetically-based fault slip rates were introduced into both the Uniform California Earthquake

Rate Forecast (UCERF) in their last update in 2013 and the National Seismic Hazard Model

(NSHM) update of 2014. This was based on the recognition that geologically-based fault slip rates have many limitations, that geodetic data (e.g., GPS) can provide independent estimates of fault slip rates, and that the abundance of geodetic data permits these rates to be estimated along many fault zones where geologically-based fault slip rates are not available. At the same time, it is recognized that geodetically-based fault slip rates require special attention because GPS networks measure instantaneous deformation rates rather than long-term rates, hence geophysical models must be constructed to interpret these data in terms of long-term fault slip rates.

2.0 SCOPE

Geodetically-based fault slip rates rely on data from Global Positioning System networks, which measure the crustal velocity field from tectonic deformation. Under the auspices of the Tectonic

Geodesy Disciplinary Group, these data are currently being assembled and will be interpreted by a team of geophysicists using physical models of crustal deformation. While a variety of models will be used (e.g., block models), all require the use of GPS data that is not contaminated by aseismic slip (also known as fault creep).

The Contractor will focus on several aspects of a key component of the geodetic slip rates models – aseismic slip on creeping faults. The fault creep not only removes fault slip from the budget of total slip dictated by tectonic plate motions, but it affects the overall interpretation of the geodetic data in terms of fault locking effects that matter for seismic hazard. The effects of fault creep must be corrected for in order for geophysical models of long-term fault slip rates to be constructed. Estimating these effects is challenging and requires considerable effort to assemble relevant data that permit identification of creeping and the discrimination of aseismic slip from fault locking. The Contractor’s efforts will include gathering the relevant data and preparing them for geophysical inversions by other members of the Tectonic Geodesy

Disciplinary Group.

3.0 APPLICABLE DOCUMENTS – NOT APPLICABLE

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4.0 TECHNICAL REQUIREMENTS

Contractor shall have the following minimum technical requirements:

a) post-graduate experience with visualization and modeling of crustal deformation data;

b) post-graduate experience with geoinformatics, particularly with radar satellite measurements of ground deformation;

c) any experience working in one or more groups on seismic hazards-related objectives.

The Contractor will collect and provide data that guides model development of aseismic fault creep, which will in turn enable other members of the Tectonic Geodesy Disciplinary Group to more accurately interpret GPS rates with fault slip rates. The Contractor will contribute to this effort in several ways:

(1) update the UCERF3 surface creep rate data set with new data that has been published in the last 10 years. This includes creepmeter, alignment array, GPS, and InSAR data. The data will be gathered from diverse sources and involve the compilation of multiple data types that must be organized, checked for quality, and evaluated for their use as constraints in geophysical inversions to characterize fault creep.

(2) Assist other group members with running inversions of geodetic data including the newly constructed creep database for the spatial distribution of fault-creep on NSHM faults in central and northern California.

(3) Evaluate estimates of the distribution of aseismic fault creep using a range of models.

This will result in a range of estimates of the distribution of fault creep that can be used as a correction to the GPS velocity field that the group will be interpreting.

The Contractor will work in concert with other members of the Tectonic Geodesy Disciplinary

Group to discuss details of the data sets and models, appraise them of progress, and coordinate how to use the suite of models to produce best estimates and associated errors of the distribution of fault creep.

5.0 DELIVERABLES

Deliverables include datasets of crustal deformation rates around recognized creeping faults, including direct measurement of creep rate across the fault as well as the distribution of deformation broadly around the faults; suites of estimates of fault creep rates and their spatial distribution on faults deemed to have significant aseismic slip. These will be provided regularly to the leader of the disciplinary group. Reports of this group will be used in order to gauge progress and guide next steps for the Tectonic Geodesy Disciplinary Group.

6.0 PERFORMANCE STANDARDS AND MONITORING METHODS

The Contractor’s progress will be reviewed at group meetings held regularly every month. The modeling efforts of the group as a whole depend on input data from the Earthquake Geology

Disciplinary group of the NSHM, as well as on data/results from The Contractor. The initial steps in The Contractor’s contributions, i.e., the gathering of relevant geodetic datasets and first-order characterization of creeping fault sources, are expected by early 2021. Model development

140G0321Q0001 Page 22 of 24 to quantitatively characterize fault creep will follow as a group effort, with preliminary fault creep models available soon thereafter. The Contractor’s data sets and models of transient deformation will be directly used in other group member’s models and may continue to be refined beyond early 2021. As this group vets its fault creep models with the NSHMP by June, 2021, all components will be reviewed by independent panels and areas of improvement recommended. This process will continue in an iterative fashion through the end of the contract period in June, 2022.

7.0 PERIOD OF PERFORMANCE AND PLACE OF PERFORMANCE

7.1 PERIOD OF PERFORMANCE IS: Date of award – JUNE 30, 2022

7.2 OPTION YEAR: JULY 1, 2022 – JUNE 30, 2023

7.3 PLACE OF PERFORMANCE IS AT CONTRACTOR’S FACILITY