Earthquake Sensation:integrating GPS and inertial sensors

Kenneth W. Hudnut, Ph.D.Kenneth W. Hudnut, Ph.D.Chief, So. Calif. Earthquake Hazard Assessment ProjectChief, So. Calif. Earthquake Hazard Assessment ProjectEarthquake Hazards Team Earthquake Hazards Team U. S. Geological SurveyU. S. Geological Survey

CENS - UCLACENS - UCLAJuly 25, 2003July 25, 2003

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Southern California is the nation’s most Southern California is the nation’s most dangerous place for earthquakes - why?dangerous place for earthquakes - why?

Silver linings:State-of-the-art earthquake monitoring arraysMany of the world’s best researchers work within this natural laboratory

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San Andreas faultSan Andreas fault• 35 mm/yr slip rate;35 mm/yr slip rate;

• >70% of total plate >70% of total plate boundary motionboundary motion

• 1685, 1812, 1857 eq’s1685, 1812, 1857 eq’s

• Big Bend compressionBig Bend compression• 1971 Sylmar (M 6.7)1971 Sylmar (M 6.7)• 1994 Northridge (M 6.7)1994 Northridge (M 6.7)

• SoCal is now heavily SoCal is now heavily ‘wired’ (much like ‘wired’ (much like Japan & Taiwan)Japan & Taiwan)

• 150+ BB CISN stations150+ BB CISN stations• 250+ SCIGN stations250+ SCIGN stations• Catalog; SCEC CMM3Catalog; SCEC CMM3

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Improving hazard assessmentImproving hazard assessment• Temporal variations do Temporal variations do

occur:occur:• Clustering (e.g., Basin & Clustering (e.g., Basin &

Range, ECSZ, Asia)Range, ECSZ, Asia)

• Discrepant geological and Discrepant geological and geodetic ratesgeodetic rates

• Sequences involving fault Sequences involving fault interaction (e.g., Joshua interaction (e.g., Joshua Tree - Landers - Big Bear - Tree - Landers - Big Bear - Hector Mine; Anatolian Hector Mine; Anatolian system, etc.)system, etc.)

• Implement robust research Implement robust research findings into hazard findings into hazard assessmentassessment

• ““Variability does not mean Variability does not mean predictability”predictability”

Courtesy Anke Friedrich

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GPS

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1st Year• Combined time

series (1996-2002)

3rd Year• Real-time earth-

quake response

5th Year• Resolve rates on

primary LA basin

faults (and others)

SCIGN Data Products

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New methods and data integrationNew methods and data integration• Precise Precise

topographic topographic mapping of mapping of surface ruptures surface ruptures and active fault and active fault scarpsscarps• slip models for slip models for

prehistoric eventsprehistoric events• rapid assessment rapid assessment

of surface slip and of surface slip and damage patterns damage patterns after large eventsafter large events

• Requires precise Requires precise integration of GPS integration of GPS & INS for flight & INS for flight navigationnavigation

1957Gobi-Altaiearthquakesurfacerupture

High resolution topography along surface rupture of the High resolution topography along surface rupture of the October 16, 1999 Hector Mine, California Earthquake (MOctober 16, 1999 Hector Mine, California Earthquake (Mww7.1) 7.1) from Airborne Laser Swath Mappingfrom Airborne Laser Swath Mapping

Hudnut, K. W. (USGS), A. Borsa (UCSD),Hudnut, K. W. (USGS), A. Borsa (UCSD),C. Glennie (Aerotec, LLC) and J.-B. Minster (UCSD)C. Glennie (Aerotec, LLC) and J.-B. Minster (UCSD)

Bulletin of the Seismological Society of AmericaSpecial Issue on the Hector Mine earthquake (2002)

http://pasadena.wr.usgs.gov/office/hudnut/docs/

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Airborne laser swath mapping (ALSM)

• precise topographic mapping of surface ruptures and active fault scarps

• representation of actual fault ruptures recorded and preserved in unprecedented detail

Airborne platform navigationmust be highly precise andrequires high-rate GPS data

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R r

v

Geolocation Vectors and Error Sources

r

Vector from CMearth to GPS phase centerMagnitude & directional errors both arestochastic, time and location variant.

R

vVector from GPS phase center to laserMagnitude error is constant if no airframe flexing. Directional error due to constant and time-varying biases in INS.

Vector from laser to ground footprintMagnitude error due to timing, instrument and atmospheric delays. Directional errorfrom constant mirror mounting offsets and time-varying biases in reporting of scanangles (both pitch and roll).

Note: additional errors due to imperfectsynchronization of GPS, INS, mirror scanand laser firing times must be modeled and removed as well.

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Lavic LakeRoll & PitchManeuvers

Explodedordnance(crater)

pitch maneuvers

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Photo byKeith Stark(SCIGN)

Maximumslipsectionof the1999HectorMine eq.surfacerupture

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Estimating Estimating slip on slip on ‘max. slip’ ‘max. slip’ segment ofsegment ofthe faultthe fault

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Laser ScanLaser Scanof the San of the San AndreasAndreasProposal to theNSF EarthScopeScience RFP:Prof. Mike Bevis, PI (OSU)

Requireshigh-rate (1 Hz)GPS datafrom SCIGNsites alongfhe fault &special carewith IMU-INS

GPS Fault Slip SensorGPS Fault Slip SensorK. Hudnut, G. Anderson, A. Aspiotes,K. Hudnut, G. Anderson, A. Aspiotes,N. King, R. Moffitt, & K. StarkN. King, R. Moffitt, & K. Stark(all at USGS-SCIGN, Pasadena CA)(all at USGS-SCIGN, Pasadena CA)

APEC symposium Proc. Paper, Fall AGU poster,and paper in preparation for

Bulletin of the Seismological Society of America

http://pasadena.wr.usgs.gov/office/hudnut/slipsensor/

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Early WarningEarly WarningEarly WarningEarly WarningThe speed of light >> the speed of sound

Seismic

and

GPS

Stations

CentralComputers Utilities

EmergencyResponse

Transport-ation(e.g; Wu & Teng, BSSA, 2002; Allen & Kanamori, Science, 2003)

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Real-Time GPS Network - Enhancing SCIGNReal-Time GPS Network - Enhancing SCIGN

• On 15 November 2002, first-ever GPS fault slip sensor On 15 November 2002, first-ever GPS fault slip sensor deployed across San Andreas fault at Gorman, Calif.deployed across San Andreas fault at Gorman, Calif.

• Augments seismic early warning system - resolves the Augments seismic early warning system - resolves the observational deficiency inherent with inertial sensors that observational deficiency inherent with inertial sensors that cannot discern tilt from accelerationcannot discern tilt from acceleration

• Upgrade SCIGN telemetryUpgrade SCIGN telemetry• DSL, frame relayDSL, frame relay• Radio repeaters, WiGate and dedicated linksRadio repeaters, WiGate and dedicated links• Data bufferingData buffering

• Augment SCIGN real-time acquisition and processing systemAugment SCIGN real-time acquisition and processing system• Implemented sub-daily processing (4 hr) for ~100 SCIGN stations Implemented sub-daily processing (4 hr) for ~100 SCIGN stations

(down from 24 hr)(down from 24 hr)• Implementing multiple real-time streaming GPS processors Implementing multiple real-time streaming GPS processors

(commercial software)(commercial software)

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Lone Juniper Ranch and Frazier Park High SchoolLone Juniper Ranch and Frazier Park High School

First prototype GPS fault slip sensor

Spans the San Andreas fault near Gorman, California

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Cleaned-up test resultsCleaned-up test resultsLJRN position variation

-0.500000

0.000000

0.500000

1.000000

1.500000

2.000000

2.500000

76000 78000 80000 82000 84000 86000 88000 90000

seconds

meters

Why is real-time GPS processing noisy and less robust than post-processing?Ambiguity resolution, multipath, atmosphere and clock errors - what can be done?

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Upgrading SCIGN telemetryUpgrading SCIGN telemetry

Low cost options such as frequent FTS dial-up, radio nets, and DSLDevelopment & testing of near real-time GPS precise processing, etc.

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Conclusions:Conclusions:• GPS and inertial sensor integration for high-GPS and inertial sensor integration for high-

accuracy applications is practical in SoCal accuracy applications is practical in SoCal because SCIGN can be readily upgraded to because SCIGN can be readily upgraded to

support centimeter-level accuracy in real-timesupport centimeter-level accuracy in real-time • Earthquake applications of Earthquake applications of

GPS/INS integration are:GPS/INS integration are:

• societally relevant - significant societally relevant - significant economic impact and economic impact and consequences would result from consequences would result from technological innovationstechnological innovations

• scientifically exciting for the very scientifically exciting for the very dynamic SCEC research dynamic SCEC research community - major breakthroughs community - major breakthroughs in earthquake source physics are in earthquake source physics are likely to result from collaborationslikely to result from collaborations