The impact of tectonic plate movement on the modernized 2022 NSRS - GPS World (2023)

It's early 2022 and the new modernized NSRS is only three years away. I hope everyone readsNGS Model Documentsupdated throughout 2021 and attendingSeries of webinars NGS. Together they provide the latest information on changes from the existing NSRS to the new NSRS.

My previous columns have highlighted many aspects of the new geopotential geometry and data framework. In this month's column I will highlight the time sensitive aspect of the modernized NSRS and why it is necessary for the new system.

As I said earlier, NOAA's National Geodetic Survey (NGS) is developing models and tools for users to transform coordinates between the four National Earth Reference Frames and the International Earth Reference Frame, Geopotential Datum and Vertical Datum. North America 1988 (NAVD 88) and the estimation of coordinates at times different from the time of observation of the survey, taking into account the movement.

What does NGS mean with estimated coordinates at times different from when the survey was made and why does the switch to the new and modernized SNRS need to be considered? This column will address these questions.

January 2022 NGS (27th edition) byNSRS modernization updatesannounced an article about the modernized NSRS and a name change to Intra-Frame Velocity Model (IFVM). See the diagram below. Users can subscribe to these newslettersHere, and you can access previous newslettersHere.

The new paper was published in October 2021 and is titled "The mathematical relationship between IFVM2022 expressed in ITRF2020 with IFVM2022 expressed in the four terrestrial reference frames of the modernized NSRS with dependency on EPP2022". is available for downloadHere.

The paper describes the mathematical relationship between the Intra-Frame Velocity Model (IFVM2022) and the Euler Pole Parameters (EPP2022).

IsNSRS modernization updatesThe announcement indicates that the name IFVM2022 has changed to Intraframe Deformation Model (IFDM2022). Helatest version of Plan 1and the October 2021 Report (NOS NGS 90) were published before the name changes, so they refer to IFVM2022 rather than IFDM2022.

Why does movement need to be considered? The coordinates change fundamentally because the earth's surface moves due to the movement of large tectonic plates. See the table below for information on why this is called plate motion or tectonic displacement. NGS understands this and tries to handle the change of coordinates by providing a time dependent component.

The NGS will define the four geometric terrestrial reference frames based on plate tectonics (see map below):

• 2022 North American Earth Reference Frame (NATRF2022)
• Pacific Land Reference Framework 2022 (PATRF2022)
• Caribbean Country Reference Framework 2022 (CATRF2022)
• Marianas Terrestrial Reference Framework 2022 (MATRF2022)

As indicated above, NGS develops models and tools to allow users to transform the coordinates between the four national reference frames and the international terrestrial reference frame and estimate the coordinates at different points in time of the survey observation time, taking into account the movement of score. These models are called EPP2022 and IFDM2022.

So what are EPP2022 and IFDM2022? And what does that mean for surveyors and cartographers?

EPP meansParameter des Eulerpols(a way to describe the rotation of a disk) and IFDM2022 is a way to calculate the offset in coordinates.

Why Euler's pole? See box Who Was Euler?

NGS's 2021 Revised Blueprint 1, NOAA Technical Report NOS NGS 62,Plan for the modernized EREN, Part 1: Geometric coordinates and ground reference framesprovides an explanation of Euler poles and "plate fixed" structures. As in "Who was Euler?" In the box, the definition of Euler's fixed point theorem states that any motion of a rigid body on the surface of a sphere can be represented as a rotation about a suitably chosen pole of rotation, called the Euler pole. The following is stated in the NOS NGS 62 report in "Plate-Fixed Frames and Euler Poles", Section 4:

If only the rigid (non-deformable) part of a tectonic plate is considered, the plate's horizontal motion (relative to a plate-independent global reference frame such as the ITRF) can be modeled as rotation about a geocentric axis. pass a fixed point. point on the earth's surface. Although such models must make certain assumptions (e.g. plate stiffness), the dominant motion of most points on most tectonic plates is rotation about a fixed point. This point is known as the "Euler Pole".

It is important to note that determining the location of a plate's Euler pole and the angular velocity at which the plate is rotating can be determined empirically using GNSS observations from a CORS mesh distributed across the plate. Figure 1 of the NOS NGS 62 report shows a graph of the Euler pole and the horizontal velocity vectors of the North American plate at selected CORS (see box titled "NOS NGS 62 Figure 1").

Figure 1 of NOS NGS 62

Every place on earth is moving. This includes adjacent markers on the same tectonic plate. This means that after removing the Eulerian motions, the remaining motions change the relative differences in the coordinates of neighboring landmarks located on the same tectonic plate. Figures 2 and 3 of the NOS NGS 62 report show plots of estimates of these remaining velocities (see boxes titled "NOS NGS 62 Figure 2" and "NOS NGS 62 Figure 3").

Figure 2 is a plot of non-Eulean motion east of 110°western longitudes. As stated in the report, most velocities are less than 2 mm/year. The concept is that the EPP2022 and IVDM2022 models eliminate both Eulerian and non-Eulerian motion of marks.

Figure 2 of NOS NGS 62

Figure 3 is a plot of non-Eulean vectors west of 110°western longitude. As indicated in the graph, the large vectors in western California, western Oregon, and western Washington show areas of deformation near plate boundaries that do not appear to be adequately captured by plate rotation alone.

Figure 3 of NOS NGS 62

It should be noted that the magnitude vectors in Figures 2 and 3 represent a different magnitude of motion. Figure 2 shows the vectors at 1-3 mm/year and Figure 3 shows the movement at 10-30 mm/year.

To better visualize the potential magnitude of the movement, I downloaded the CORS ITRF2014 coordinates and velocitiesWebsite NGSand compiled the results. See boxes titled "Cors ITRF 2014 Horizontal Velocity" and "Table of ITRF 2014 Horizontal and Upward Velocity of U.S. CORSs".

CORS ITRF 2014 horizontal speeds

Calculated speeds only (downloaded on January 13, 2022)

The graph titled CORS ITRF 2014 Horizontal Velocity provides the horizontal vectors based on the NGS file downloaded on January 13th. Only the CORS speed identified as operational and calculated has been included in the graph.

I've also created a table summarizing the ITRF rates for CORS marked as part of the United States. The table includes the following information for each U.S. state and territory:

1. Number of CORS
2. Minimum horizontal speed (mm/year)
3. Maximum horizontal speed (mm/year)
4. Average horizontal speed (mm/year)
5. Minimum ascent rate (mm/year
6. Maximum ascent rate (mm/year),
7. Average ascent rate (mm/year).

See table below.

US CORS ITRF 2014 horizontal and rate of climb chart

Calculated speeds only (downloaded on January 13, 2022)

The areas highlighted in the table are not on the North American plate (GU, HI, PR, and VQ), and the highlighted states are partially on or near the North American plate boundary (CA, OR, WA). This is one of the reasons why its minimum and maximum horizontal speed values ​​are different from most other state values.

To visualize the relative differences in horizontal velocities between neighboring CORS, I have plotted the ITRF 2014 horizontal velocities for the CORS in North Carolina (see box titled "Cors ITRF 2014 Horizontal Veloties in North Carolina"). Looking at the figure it is obvious that all speeds are around 14 mm/year and moving in the same direction.

CORS ITRF 2014 Horizontalgeschwindigkeiten in North Carolina

Calculated speeds only (downloaded on January 13, 2022)

I have plotted the horizontal velocities for Missouri to give an example of velocities in the contiguous Midwest. The magnitude of the velocities is similar to North Carolina, but the direction of the vector is slightly different. North Carolina average horizontal velocity is 14.1 mm/year and Missouri average horizontal velocity is 14.6 mm/year.

CORS ITRF 2014 horizontal speeds in Missouri

Calculated speeds only (downloaded on January 13, 2022)

To highlight the differences along the boundaries of the tectonic plates, I've included a CORS ITRF 2014 horizontal velocity chart for the state of Oregon and a chart for states along the west coast of the United States. See boxes titled CORS ITRF 2014 Horizontal Velocity in Oregon and CORS ITRF 2014 Horizontal Velocity Along the West Coast of CONUS. As indicated in the graph, there are significant changes in horizontal velocities near the Oregon coast. Values ​​decreased from inland CORS to coastal CORS by about 10 mm/year.

CORS ITRF 2014 horizontal speeds in Oregon

Calculated speeds only (downloaded on January 13, 2022)

The graph of CORS ITRF 2014 horizontal velocities along the west coast of CONUS clearly shows the change in magnitude the closer the CORS is to the Pacific and Juan de Fuca plates.

CORS ITRF 2014 Horizontal velocities along the west coast of CONUS

Calculated speeds only (downloaded on January 13, 2022)

I've also included a graph of Alaska's horizontal speeds for completeness.

CORS ITRF 2014 horizontal speed in Alaska

Calculated speeds only (downloaded on January 13, 2022)

To better visualize the horizontal and upward velocity of CORS across states, I have plotted the average horizontal and upward velocity for each state as a function of that state's CORS. See the table titled Average Speeds by State.

Average speeds by state

I also calculated an average horizontal velocity value based on CONUS CORS east of 110°west longitude (given here as a regional horizontal velocity value). [I used CORS east of 110°west longitude to match NGS Figure 2 in NOS NGS 62.]

The chart below summarizes the average horizontal movement for each state. The table offers:

1. Or CORS number east of 110°longitude east
2. Average horizontal speed (mm/year)
3. Average horizontal velocity minus regional horizontal velocity (mm/year).

This provides an estimate of the variations in relative horizontal movement between states.

ITRF 2014 horizontal speed table minus US CORS regional speed east of 110°longitude east

The chart titled "NC Horizontal Velocities minus Average Velocity" shows the resulting horizontal velocities with average velocity removed (average velocity was based on NC CORS only) for all CORS in North Carolina. As can be seen from the diagram, most of the resulting horizontal velocities are less than 1mm/year, but still not zero. Again, this is just to give you an idea of ​​the magnitude of the relative vectors between CORS in North Carolina.

As indicated in the NOS NGS 62 report, these horizontal velocities will be small but not zero. Therefore, the NGS must provide templates and tools for users to convert the coordinates between the four national frameworks (NATRF, PATRF, CATRF and MATRF) and the International Terrestrial Reference Framework (ITRF).and estimating the coordinates at different points in time of the survey observation time, taking into account the movement within the frame of reference. California surveyors have studied this type of movement for many years.

Horizontal speeds in NC minus average speed

(Downloaded January 13, 2022)

I have plotted the 2014 ITRF slew rate values ​​from CORS in North Carolina to present an estimate of CORS vertical motion in North Carolina. See the diagram below. The values ​​of the vertical velocities are much smaller than the horizontal velocities, but they are still not zero. A future column will look at up-velocities based on ITRF 2014 rates and crustal motion models.

Upward speed from CORS ITRF 2014 in North Carolina

(Downloaded January 13, 2022)

This column explains why it is important to consider ridge movement everywhere, not just in areas affected by active earthquake-induced crustal movement, such as Southern California. Providing information on CORS movement rates based on NGS ITRF2014 coordinates and speed information. He highlighted NGS reports that describe templates that make it easier for users to transfer coordinates between frames of reference and to manipulate movements within the frame between markers based on surveys performed at different times. This isn't just a horizontal placement issue.

A future column will deal with estimates of vertical velocities in the new modernized NSRS.