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Group E homepage

Group E will continue to improve the SCEC Crustal-Motion Map, and apply it and other high precision geodetic measurements to the tasks in this RFP. We seek proposals that address these tasks, that are within our broad discipline, and that apply creative approaches to such problems as strain estimation, fault interaction, and post-seismic behavior.

Group E efforts are primarily divided between infrastructure and science. In the Infrastructure category, we include (1) ongoing support of observational systems, (2) data collection and routine processing relevant to the Crustal-Motion Map, and (3) collection of time-sensitive data from the region of the Hector Mine earthquake. In the Science category, we encourage projects that would use data or products from the Crustal-Motion Map project, or the SCIGN network, in innovative ways. We also include an element of documentation of the group's efforts for the legacy document.

In order to respond to the Hector earthquake, several groups within SCEC WG E re-directed funds from other projects. We will therefore consider proposals to complete such projects from those groups which did redirect funds.

I. Infrastructure:

a. Continued SCEC contribution towards operation of the SCIGN network, to provide a regional framework for other GPS studies and to begin to elucidate more details of deformation in the Los Angeles region. This also will support SOPAC contributions to the Crustal-Motion Map.

b. Operation of PFO to provide a continued detailed time history of strain variations in southern California.

c. Improvements and additions to the SCEC Crustal-motion map (formerly velocity map). This should be presented as a joint proposal with individual budgets, to include the following elements:

1. Archiving past data, and also data collected under (d), and any useful data collected by other groups. Given that most older data has been archived, the level of support for this should be less than in previous years.

2. Processing all data in a consistent fashion, to producing a time series for all locations. This could also include software support: though since the software and the processing are largely "mature", the support for either should be less than in previous years.
3. Estimating station velocities (including time variations where relevant) as the final product to be distributed.

Because of the Hector Mine earthquake, additional survey-mode GPS fieldwork will not improve the precision of velocities for most of Southern California. Such fieldwork would thus not be funded this year.

d. Survey-mode observations at points in the vicinity of the Hector earthquake. Data collection should have the purpose of (a) improving coseismic models by occupying points with pre-earthquake data close to the rupture; (b) continuing measurements at points for which a history of post-earthquake measurements exists, to construct a picture of the immediate postseismic response; (c) measurements at new points to provide a deformation "snapshot" against which later measurements might be compared. It is assumed that (a) and (c) points would be occupied only to the extent needed to create reliable data. The total plan will be submitted as a joint proposal with multiple budgets.

II. Science

a. Interpretation of crustal-motion map: how to convert from velocity to strain to hazardous strain; physical models and improved coseismic models to fit the observed velocities and offsets; stress interaction and evolution.

b. What geodetic signals are expected from geophysical or geological models, especially in the Los Angeles region?

c. Postseismic phenomena: Are there regional, long period signals? If so, how may they be explained? What observations are diagnostic for different possible mechanisms? Are there changes in aseismic slip rate on neighboring faults following moderate to large earthquakes in the region (e.g., Landers and Northridge)? What can be learned about co-seismic slip heterogeneity?

d. How can we infer stress change, especially at seismogenic depths, from surface displacements?

e. What is an accurate error model for continuous GPS data?

III. Legacy Document

It is envisaged that the Group E contribution to this would take two forms. First, a technical paper describing the production of the Crustal Motion Map: this would be suitable for publication as a journal article, though a longer version (with, for example, more tables) could be a SCEC publication. Second would be a "semi-technical" paper, intended for professionals with an interest in ground deformation, explaining in simple terms how crustal motion affects precise measurements, and what the SCEC product is. SCEC product.

Software and Tools

The online manual and online registration web page http://gipsy.jpl.nasa.gov/qoca contains GPS data post-processing tutorial and SCEC
related activities. It might be useful for SCEC community.