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SCEC Community Geodetic Model (CGM) Workshop

Conveners: Jessica Murray, David Sandwell, and Rowena Lohman
Dates: May 30-31, 2013
Location: Vallombrosa Center, Menlo Park, CA
Participation: by invitation only
SCEC Award: 13077

OVERVIEW: The goals of the 2013 Community Geodetic Model (CGM) Workshop are (1) to further develop the big-picture plan for generating the CGM including the overall approach and milestones, (2) produce a concrete list of initial tasks with a strategy and timeframe for completing them, (3) identify members of the SCEC community who will actively contribute to model development. This will involve establishing the requirements, for example, with respect to spatial and temporal resolution, for the model as driven by its envisioned applications. Also necessary will be assessments of the achievable level of precision and associated resolving power that are feasible given available data, the possible addition of new data, and the capabilities of approaches for combing GPS and InSAR time series.

Agenda items for the CGM workshop include:

  • Develop a list of anticipated applications for the CGM.
  • Define the features, spatial and temporal resolution, and precision required for each application.
  • Assess what data are available and where more data are needed to meet requirements.
  • Evaluate which approaches to GPS and InSAR time series analysis are most appropriate and what assumptions these methods embody.
  • Identify best approaches for combining data types and consider how aspects such as weighting, smoothing, or interpolation will contribute to uncertainties.
  • Consider whether more research is needed to further develop new approaches and, if so, in what areas.
  • Explore strategies for comparing and validating input and methods used in the CGM.
  • Solicit ongoing participation by investigators who will contribute and assimilate data analysis and models to produce the CGM.
  • Discuss strategies for maintaining the CGM, once developed, as new data become available.

We envision the CGM workshop to include presentations on data analysis methods and anticipated CGM applications, as well as a significant amount of time for discussion. To stimulate dialogue on analysis methods, we propose to assemble a large stack of interferograms prior to the workshop which interested participants can use to produce InSAR time series employing methodology of their choice. Results will be compared at the workshop to identify best practices for development of the full CGM. Synthetic data will also be used to frame a candidate workflow for combining InSAR and GPS data into a time series product and to explore the relative contribution of the two data types to the final product.

To achieve the workshop goals it will be necessary to bring together a diverse but targeted group of scientists representing likely CGM users and those with expertise in geodetic data analysis, integration, and modeling. At the CSM workshop held in October 2012, it became clear that the CGM will be an important resource for the CSM effort and that there is substantial overlap among researchers involved in the CSM and those whom we hope to involve in the CGM. Therefore CGM Workshop in conjunction with the 2013 SCEC CSM Workshop, which will allow us to obtain input from a broad spectrum of potential users on required features of the CGM.

PARTICIPANTS (29 total): Duncan Agnew (UCSD), Scott Baker (UNAVCO), Greg Beroza (Stanford), Roland Burgmann (UC Berkeley), Ksenia Dmitrieva (Stanford), Yuri Fialko (UCSD), Mike Floyd (MIT), Gareth Funning (UCR), Jeanne Hardebeck (USGS), Liz Hearn (USGS contractor), Tom Herring (MIT), Bill Holt (SUNY at Stony Brook), Tran Huynh (USC), Kaj Johnson (Indiana), John Langbein (USGS), Eric Lindsey (UCSD), Zhen Liu (NASA JPL), Rowena Lohman (Cornell), Betsy Madden (UMass), Sally McGill (CSU San Bernardino), Jessica Murray (USGS), Sue Owen (NASA JPL), Fred Pollitz (USGS), David Sandwell (UCSD/SIO), Manoocherhr Shirzaei (ASU), Josh Spinler (U Arizona), Wayne Thatcher (USGS), Xiaopeng Tong (UCSD), and Yuehua Zeng (USGS)

Presentation slides may be downloaded by clicking the pdf links following the title. PLEASE NOTE: Slides are the author’s property. They may contain unpublished or preliminary information and should only be used while viewing the talk.

THURSDAY, May 30, 2013

13:00-13:10 Welcome and Workshop Goals J. Murray
13:10-13:15 Opening Remarks from SCEC Leadership G. Beroza
  Session 1: Target Applications for CGM
Moderator: F. Pollitz; Recorder: L. Hearn
13:15-13:25 CGM as envisioned in the SCEC4 proposal J. Murray
13:25-13:35 CGM as input for studies of the ductile rheology of the lithosphere: report from May 1-2, 2013 workshop L. Hearn
13:35-13:45 CGM as input for developing the Community Stress Model: report from the May 29-30, 2013 workshop J. Hardebeck
13:45-13:55 CGM as a time dependent reference frame for transient detection R. Lohman
13:55-14:05 CGM as input for hazard assessment K. Johnson
14:05-14:15 CGM as input for modeling studies - Part 1 Y. Fialko
14:15-14:25 CGM as input for modeling studies - Part 2 W. Holt
14:25-15:00 Discussion
  • What level of spatio-temporal resolution is needed?
  • What level of precision?
15:00-15:15 Break  
  Session 2: GPS and Older Geodetic Data
Moderator: S. McGill; Recorder: W. Thatcher
15:15-15:25 Lessons learned from CMM and summary of pre-GPS data available D. Agnew
15:25-15:35 Continuous GPS data for southern California – the PBO combined analysis T. Herring
15:35-15:45 Continuous GPS data for southern California – JPL ARIA project S. Owen
15:45-15:55 Campaign GPS data for southern California M. Floyd
15:55-17:30 Break-Out Groups: Initial Brainstorming in Preparation for Tomorrow's Discussion
  • What is needed?
  • What is possible?
    • Velocity fields and strain rates from GPS and InSAR
    • Time series of crustal motion from GPS and InSAR
18:00-19:00 Dinner, served in Vallombrosa Dining Room  

FRIDAY, May 31, 2013

08:00-09:00 Breakfast, served in Vallombrosa Dining Room  
  Session 2: GPS and Older Geodetic Data (continued)
Moderator: S. McGill; Recorder: W. Thatcher
09:00-09:10 A reprocessed GPS velocity field for the western U.S. Y. Zeng
09:10-09:20 Noise in GPS time series 1: Appropriate noise models J. Langbein
09:20-09:30 Noise in GPS time series 2: The contribution of random walk noise K. Dmitrieva
09:30-10:00 Discussion
  • What are major noise sources?
  • How good is our spatial/temporal coverage?
  • What additional sources of GPS data might be likely to be available in the future (e.g., new CGPS sites)?
10:00-10:15 Break  
  Session 3: InSAR Data
Moderator: J. Murray; Recorder: M. Shirzaei
10:15-10:25 Current data availability in UNAVCO and ASF archives S. Baker
10:25-10:35 Limitations and noise sources of current data D. Sandwell
10:35-10:45 Future SAR missions D. Sandwell
10:45-10:55 InSAR time series analysis techniques overview R. Lohman
10:55-11:30 Discussion
  • How good is our spatial/temporal coverage?
  • What can we do with what we have?
  • What type of InSAR data are needed to do a good job of recovering things at the few mm/yr scale?
  • To what extent can we mitigate the major noise sources?
  • What opportunities might new missions present?
  Session 4: How to Bring the Datasets Together
Moderator: R. Lohman; Recorder: D. Sandwell
11:30-11:40 Approaches to combined use of InSAR and GPSs
Model-based integration assuming constant velocity
X. Tong
11:40-11:50 High spatial resolution of creeping faults E. Lindsey
11:50-12:00 Spatial and temporal resolution of Hayward Fault M. Shirzaei
12:00-13:00 Lunch, served in Vallombrosa Dining Room  
13:00-13:10 Time series monitoring of deformation Z. Liu
13:10-13:20 Combined software tools R. Lohman
13:20-13:30 Integration of GPS and InSAR for resolving postseismic deformation R. Burgmann
13:30-13:40 How to characterize the errors in the CGM and its components? G. Funning
13:40-14:30 Discussion
  • What would a combined “data product” look like? (E.g., what basic and derived quantities do we want to provide?)
  • How independent are GPS and InSAR-derived observations of crustal motion? What are the strengths and weaknesses of a combined solution?
  • What methodological advances to data analysis/combination would help?
  • What metadata must be provided with the CGM?
14:30-14:45 Break  
  Session 5: Development of Milestones and a Prioritized Task List; Distribution of Tasks Among Participants
Moderator: D. Sandwell; Recorder: R. Lohman
R. Lohman, recorder
14:45-14:55 Do we need additional data? Where? - Part 1 W. Thatcher
14:55-15:05 Do we need additional data? Where? - Part 2 S. McGill
15:05-16:00 Discussion
  • What are the basic building blocks that must be completed first?
  • Who is already conducting work that contributes to this? How to encourage additional participation (e.g., through RFP)?
  • How do we keep the CGM up-to-date in the out-years?
  • Revisit and revamp the milestones
16:00 Adjourn