SOPAC's Instantaneous Global Plate Motion Model:

1. SOPAC's Instantaneous Global Plate Motion Model: Contributions to a North America Fixed Reference Frame Yehuda Bock, Linette Prawirodirdjo, Peng Fang, Paul Jamason, Shimon Wdowinski (TAU, UMiami) Scripps Orbit and Permanent Array Center Institute of Geophysics and Planetary Physics Scripps Institution of Oceanography University of California San Diego La Jolla, California 2004 Joint Assembly Montreal, CANADA May 18, 2004

2. Introduction • SOPAC estimates monthly a global plate motion model (17 major and minor plates) based on its daily CGPS position time series. • Longest time series are 13 years old, beginning during the “GIG” experiment in January 1991. Shortest time series are about 4 years old. • Plate motion model is based on CGPS stations whose data are publicly available so that it can be easily used/replicated by other researchers.

3. GPS Data Analysis • Entire daily time series have been re-estimated by SOPAC in a consistent manner after a reconciliation of all site metadata in the SOPAC archive. • Time series are from 24-hour GAMIT solutions of 20 sub-networks, including 4 global and 16 regional sub-networks with overlapping sites. • Sub-networks are combined daily with the GLOBK glorg module, aligned by a 7-parameter similarity transformation to ITRF2000 as realized by the IGS, thereby maintaining the No-Net-Rotation condition of ITRF2000 wrt to NNR-NUVEL-1A.

4. Time Series Analysis • Modeled with linear rates (velocities), annual and semi-annual parameters, offsets (instrumental and coseismic), and postseismic decay. • Coefficients of a white noise plus flicker noise model are estimated by MLE approach, and propagated to uncertainties of time series parameters.

5. 13-Year Daily (Unfiltered) Time Series at PIN1 & PIN2 PIN1 velocities: N5.4±0.5;8.0±0.8 E-27.1±0.6;-27.0±0.8 U2.8±1.7;2.7±2.6 PIN2 velocities: N5.4±0.5;7.5±0.7 E-27.4±0.7;-26.6±1.0 U2.6±1.3;4.1±1.9 RMS: H 3-4mm;V 9mm

6. Typical NA Time Series Used in PMM

7. NA Time Series Excluded from PMM

8. Plate Motion Model • Stations that exhibit “anomalous” behavior are excluded (e.g., elastic and seismic deformation, significant vertical motion). • Estimate Euler poles by minimizing site velocities relative to ITRF2000. • Include in the rigid plate motion estimates only stations whose velocity residuals are less than the 2 s velocity uncertainties. • This leaves us with about 110 global sites.

9. Velocity differences between SOPAC and ITRF velocities and comparison of velocity error ellipses – 95% confidence).

10. Vertical Motions

11. SOPAC Plate Motion Model

12. North America Reference Frame

13. Examples of Use of Plate Motion Model

14. SOPAC Online Map Interface

15. Analysis of SCEC III Crustal Motion Model Shen et al., 2003

16. LatitudinalComponent Longitudinal Component

17. California Spatial Reference Center (CSRC) • Provide the necessary geodetic services to ensure the availability of accurate, consistent, and timely spatial referencing data. • Monitor temporal changes in geodetic coordinates due to tectonic motion, earthquakes, volcanic deformation and land subsidence. • Establish the legal spatial reference system for California (the “CSRS”).

18. California Spatial Reference System

19. SECTOR and CSRS Epoch 2004.0 CSRS Epoch 2004.0 is defined as the coordinates (and velocities) computed by CSRC on 14 April 2004 using data up to an including 27 March 2004, and will not change.

20. Monthly SOPAC PMM Updates • SOPAC estimates monthly a global plate motion model (17 major and minor plates) to improve precision and reliability as new data become available. • Plate motion model is based on CGPS stations whose data are publicly available so that it can be easily used/replicated by other researchers. • The SOPAC PMM provides a baseline against which anomalous motions (tectonic or otherwise) can be detected.