An updated Canadian GPS velocity field using NRCan’s Precise Point Positioning (PPP) Software – Plans and preliminary results J. Henton 1, M. Craymer 2, M. Piraszewski 2 and E. Lapelle 2 1 Geodetic Survey Division, Natural Resources Canada (Sidney, BC) 2 Geodetic Survey Division, Natural Resources Canada (Ottawa, ON)

National-Scale PPP Processing  Introduction & Rationale  Scope of Processing Effort  Preliminary Results  Summary of Plans  Acknowledgements Examples of Other NRCan Applications for PPP Results (Successes, Opportunities, Challenges) Presentation Outline

 In an effort to continuously improve and refine previous continental-scale GPS velocity fields for Canada (in particular), we process data from nearly all continuous GPS (cGPS) sites in Canada, the northern portions of the US including Alaska, Greenland as well as a set of global sites used to define the reference frame.  In addition, repeated high accuracy campaign surveys of the Canadian Base Network (CBN) are included in our analyses.  Results from NRCan’s PPP software will be integrated with cGPS & CBN solutions for increased redundancy. Introduction

 Contribute to the NAREF initiative  Generate a national Canadian velocity grid for interpolation to any point  Support national and regional NRCan studies of geophysical processes Rationale

NORTH AMERICAN REFERENCE FRAME (NAREF) OBJECTIVES IAG Sub-commission 1.3c (Regional Reference Frames for North America)  To densify the ITRF reference frame in North America  Consolidate regional networks into a continental one  Integrate into ITRF via IGS global network  Produce coordinate solutions – Weekly solutions/combinations – Cumulative solutions with velocity estimates Rationale – NAREF Initiative

 High accuracy cGPS sites in Canada, northern US (Great Lakes) & Alaska, and Greenland;  Data spanning 2000 (TBC) to “current”  Processing with Bernese 5.2 & NRCan PPP (using latest IGS satellite products);  Global IGS sites included to define reference frame;  Cumulative solution (coordinates and velocities) produced using NRCan’s updated SINEX_COMBINE software;  Using ITRF-published set of time series discontinuities for ITRF sites  Examine time series of all sites for additional discontinuities Scope of Processing Effort - Continuous GPS (I)

Scope of Processing Effort - Continuous GPS (II) CBN Sites RF Sites Based upon previous “GSB” (GSD Bernese v5.0) Solution & Combination: ▪ 568 sites ▪ 2000– ▪ 589 weekly solutions  New effort will include more cGPS sites.

Scope of Processing Effort - Continuous GPS (III) Global RF Sites Based upon previous “GSB” (GSD Bernese v5.0) Solution & Combination: ▪ 117 global IGS sites used to define reference frame (RF).  New effort will be updated to include current IGS RF sites.

 Repeated survey campaigns of the Canadian Base Network (CBN)  Network of stable pillar monuments  Forced centering antenna mounts  Covers mainly southern half of Canada (sparser in north)  Multiple (3-4) 24 hr occupations of each site  60 survey campaigns from 1994 to “current”  1st national campaign1994 – 2000 (no 1998)  2nd national campaign2001(east) – 2002(west)  3rd national campaign2005(east) – 2006(west)  4th national campaign2010(east) – 2011(west)  Many smaller campaigns occupied a few CBN sites Scope of Processing Effort - Episodic GPS (I)

CBN Sites RF Sites Scope of Processing Effort - Episodic GPS (II) ▪ Use identical procedures & softwares as for continuous processing; ▪ Stack daily solutions into campaign solutions

Results: Vertical Rates (Previous Combination) ▪ GSB & CBN solutions (rates & coordinates both aligned and integrated with ITRF2008 ▪ GIA signal is apparent across Canada. ▪ Also, signals from western plate margin deformation processes are present.

Results: Regional Preliminary PPP Vertical Rates [from: James et al (2012), 2012 AGU Fall Meeting]

Results: Regional Comparison of Vertical Velocities Plot Courtesy of Andrea Darlington (NRCan & UVic)

 We have begun to process GPS data with NRCan’s Precise Point Positioning (PPP) software using the most current IGS orbits, precise clocks and absolute antenna calibrations together with the Vienna Mapping Function (VMF1) for the tropospheric model.  The PPP software is efficient for processing large arrays and preliminary rate results have proven comparable to those from Bernese (v5.0).  Soon, we will initiate PPP processing (and integrated solutions) for all GSB & CBN sites to provide complete redundancy for the Bernese (v5.2) results. Summary – General Plans for National PPP Processing

 Evaluate other processing and analysis products (e.g.):  VMF1 products from University of New Brunswick (UNB)  Atmospheric pressure loading (and other loading) corrections  Implement procedures to produce PPP “network” coordinate files using GSD’s updated SINEX software  Begin integration with new GSB solutions (and NAREF?)  Automate search for discontinuities in all time series  Generate cumulative (coordinate & rate) solutions  Using updated SINEX_COMBINE software  Routine cumulative solutions (rather than as-needed) Summary – Specific (Near) Future Plans

 Provincial geodetic agencies for providing access to their cGPS data;  GSD and provincial geodetic agencies for installation of highly stable CBN monumentation;  GSD field survey personnel for consistently providing highly accurate GPS survey campaigns;  François Lahaye (GSD) for support with PPP software (on behalf of the PPP development team);  Rémi Ferland (GSD) for SINEX combination software and support;  Andrea Darlington (GSC & UVic) for preliminary PPP analyses. Acknowledgements

 Relative Sea-level (RSL) Projections  Spatial variation in vertical land motion  Direct downstream application for national PPP analyses  Episodic Tremor & Slip (ETS) Studies  Looking for improved (e.g. sub-daily) temporal sampling  Specialized, as-needed, and regional  Earthquake Rupture Monitoring  Real-time kinematic positioning  Discrimination of potential tsunamigenic events  Focus of upcoming talk by Schmidt et al. Applications – Successes, Challenges & Opportunities

Regional RSL Studies: GPS Vertical Rates (PPP) ▪ Land subsidence in Nova Scotia, with transition to uplift at the mouth of St. Lawrence River ▪ Pattern is consistent with paleo-sea-level record, and with models of postglacial rebound (PGR) from: James et al (2012), 2012 AGU Fall Meeting

Regional RSL Studies: Tide Gauge Trends [from: James et al (2012), 2012 AGU Fall Meeting]

Regional RSL Studies: Eustatic Sea-level Change Tide Gauge Trend minus GPS Trend ▪ Average observed sea-level change is 1.8 ± 0.7 mm/yr (tg analysis ends 2006) ▪ (Weighted average 2.0 mm/yr) ▪ IPCC AR4 20 th century global estimate is 1.8 ± 0.5 mm/yr  Success: Comparison gives confidence in GPS uplift rates. [from: James et al (2012), 2012 AGU Fall Meeting]

Cascadia ETS Studies - Introduction Image Courtesy of Herb Dragert (NRCan) Deep Slip Event

Cascadia ETS Studies – Signal from Strainmeter Site ▪ Borehole strainmeters (BSM) provide a continuous precise deformation signal. However the distribution of these instruments is more limited than GPS sites and they can be affected by large non-tectonic signals (e.g. drift & hydrological loading).

Cascadia ETS Studies – Signal from GPS Site  Challenge: To better constrain the timing of ETS migration, can we achieve precise sub-daily positions through PPP?

Earthquake Monitoring Studies ▪ For the Tōhoku earthquake (and aftershocks) NRCan’s carrier-phase correction service HPGPSC is used to simulate real-time epoch-by-epoch positions.

Earthquake Monitoring Studies – Offsets I Elastic model deformation from a simplified Nootka Fault Zone strike-slip earthquake (M w = 7.35) ELIZ ΔE = m ΔN = m ΔU = m NTKA ΔE = 0.281m ΔN = m ΔU = 0.023m

ELIZ ΔE = m ΔN = m ΔU = m NTKA ΔE = m ΔN = m ΔU = m Elastic model deformation from a simplified Explorer Plate subduction earthquake (M w = 8.15) Earthquake Monitoring Studies – Offsets II