24.applications and examples

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12.540 Principles of Global Positioning SystemsSpring 2008

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12.540 Principles of the GlobalPositioning System

Lecture 24Prof. Thomas Herring


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OVERVIEW

Examination of results from Earthscope Reference frame definition: SNARF High-rate GPS results Episodic Tremor and Slip (ETS) events Two types of water events.

Tools

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PBO GPS Data Analysis

ACs (NMT and CWU) are routinely generating PBOGPS data products Rapid Sinex files: 24 hour latency Final Sinex files: 6-13 day latency, weekly run started after IGS final

products become available Supplemental Sinex files: 12-week latency, weekly run. Includes

missed sites and a 3-4 tie sites from final runs to link network. Testsshow performance similar to finals. Bias fixing not quite so good due

typically to wider site spacing. Supplemental runs also add sites to original final submission (until re-

processing generates new set of final runs). SINEX and RMS files ftpd to MIT

Recently campaign processing (Bob Smith) added to processing firstas an additional run similar to the supplemental runs and oncecaught up, included in the supplementals.

Added USGS processing of SCIGN sites (SCEC funding). Resultsappear in combined product.

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PBO Combination Analysis

ACC: Rotates, translates, and scales each AC to PBO SNARF

reference frame; check and correct meta data (when possible) Combine AC results and transforms combined product to PBO

SNARF (Stable North America Reference Frame)

Outlier checks and report generated SINEX and time-series files sent to UNAVCO via LDM The PBO realization of SNARF is updated about once-per-year:

Requires re-submission of all frame defined sinex files and time

series files. Latest version 20070919173418. At 6-monthintervals updates are made for new stations. (Reference framesites are not updated in these incremental updates and thus thetime series and SINEX do not need release.

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PBO SNARF Reference Frame

Red: IGSreference

sitesYellow

PBO/Nucleus

sites

254 sites used to estimate daily rotation, translation and scale ontothe North America Frame. Outlier detection during estimation.

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RMS dailyscatter: PBO

Sites

Daily RMS Scatters for 2004-2007.9 Combined solution for PBO Sites

Median North 1.1 mmMedian East 1.4 mmMedian Height 3.9 mm

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Daily RMS Scatters for 2004-2007.9 Combinedsolution for Nucleus Sites

Median North 1.2 mmMedian East 1.4 mmMedian Height 4.2 mm

Daily RMSScatters:

Nucleus Sites

Nucleus are pre-

existing GPSsites that will bemerged into PBOat the end of construction(10/2008).

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NorthernCaliforniasites

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Central US

The RG sites aremostly onlyprocessed byCWU and theresults are very

noisy.Only one the RGsites is meant tobe processed byCWU.

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SCIGN site analysis:

These resultshave implicationsfor how wellexternal or campaignprocessing canincorporated intoPBO.

Current analysislooks very good.

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Median North 1.1 mm

Median East 1.3 mmMedian Height 3.8 mm

RMS Scatter of

merged SGIGNsites

Quality is verysimilar to other PBO sites.

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Arrival of surface

waves from SanSimeon Earthquake(1-Hz)

GPS stationsaround Parkfieldoperate at 1-Hz

sampling rates,which allows us tostudy surface wave

arrivals from nearbyand largemagnitudeearthquakes

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Time zoom of arrivals

In addition to thesurface waves, thestatic co-seismicoffset can also beseen here.

Real time high rateGPS data useful for surveying andengineeringcommunities.

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Episodic Tremor and Slip (ETS)events in Casadia (Pacific North West)

Examine overlay of strainmeter results and GPS coordinates Strainmeters measure small displacements in bore-hole (10-cm

diameter) to measure strain (dl/l). GPS measures the integratedeffects of all strains between site and stable North America. Strain meter data downloaded from:

http://pboweb.unavco.org/?pageid=89 level 2 processed data (ASCIIform)

Files give gauge data calibrated to strain units with correctionsoffsets, trends and tides.

Four gauge readings converted to 3 components of strain in east,north and EN directions (Eee-Enn, Eee+Enn, 2Een) through gaugeorientations and least-squares (could test rms here).

Eee-Enn strain compared GPS East coordinates after removingpolynomial from strain.

Data available in a number of formats including SEED

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http://pboweb.unavco.org/?pageid=89http://pboweb.unavco.org/?pageid=89


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Image removed due to copyright restrictions.
http://www.navteq.com/http://www.terrametrics.com/http://www.europa-tech.com/


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Borehole strainmeter GPS comparisonTransient appears shorter in strain record? However is this expected fromspatially transient strain event: Position will see continued integration

Green line includes tides


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Comparison in Northern Casadia/Vancouver Island

Again short strain event but here earlier signal in Nov 2006not seen in GPS.Again short strain event but here earlier signal in Nov 2006

not seen in GPS.


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Motions in California

Red vectors relative to North America;Blue vectors relative to Pacific

Motion acrossthe plateboundary is ~50mm/yr.

In 100-years thisis 5 meters of motion which isreleased in largeearthquakes

Look atmotion here 20


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Site BBDM (using GoogleEarth)

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Courtesy of MDA EarthSat . Used with permission.
http://www.mdafederal.com/homehttp://www.mdafederal.com/homehttp://www.mdafederal.com/home


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Site BBDM (DM means Dam*)

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Water level in DAM versus site east coordinate

0.2 5

0.18

0.16

0.14

0.12

0.1

0.08

V o

l ( a c r e -

f e e

t ) 1 e

6 0

-5

E a s t R

a t e

r em ov

e d ( mm

)

Vol (acre-feet) 1e6

East Rate removed (mm)

0.06 -10

2000 2001 2002 2003 2004 2005 2006Year

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Closer Look (water change is rapid)

V o

l ( a c r e

- f e e

t ) 1 e

6

0.2

0.18

0.16

0.14

0.12

0.1

0.08

0.062004 2004 2005

Year

5

0

-5

Vol (acre-feet) 1e6

East Rate removed (mm)

-102006 2006

E a s t R

a t er

em ov

e d ( mm

)

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Another Water effect

2005-AnomalyBaldwin Park Areas

Velocity LegendRed: 2003-2005;Blue 2005-2005.5;Black 2005.5-2007

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Trend fit


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Baldwin Hills

Velocityanomaly

Change in velocity

(2003-2005) minus(2005.5-2007.)95% confidenceellipses

Grey scaledversion of 2005rate

Rapid responsethought be dueto water; reasonfor long term

change not clear 30


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Summary of Water Effects

While onset on motion in 2005 in Baldwinregion coincides with heavy rains; the motionsin this region continue well after the end of

rains. BBDM: Dam site shows rapid response to

water changes in the dam and so effect inbasin seem to be of a different nature.

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Cautions: Bad antenna artifact (several sites of this nature)


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Cautions: Bad antenna artifact (several sites of this nature)

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Repeating slow

earthquakes inPacific North West

Example of repeatingslow earthquakes (norapid rupture)

These events giveinsights into material

properties and nature of time dependence of deformation

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Please see: Larson, K., P. Bodin, and J. Gomberg . Using 1 Hz GPS Data to Measure

Deformations Caused by the Denali Fault Earthquake. Science 300 (2003): 1421-1424.


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Tools

Most modern GPS analyses now containhundreds of GPS sites

For the remainder of the lecture we examine

results with the GAMIT/GLOBK matlab toolsavailable at:http://www-gpsg.mit.edu/~tah/GGMatlab

Current programs are velview and tsview.

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http://www-gpsg.mit.edu/~tah/GGMatlabhttp://www-gpsg.mit.edu/~tah/GGMatlab

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