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CENS - UCLA July 25, 2003 Earthquake Sensation: integrating GPS and inertial sensors Kenneth W. Hudnut, Ph.D. Chief, So. Calif. Earthquake Hazard Assessment Project Earthquake Hazards Team U. S. Geological Survey

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Earthquake sensation integrating gps and inertial sensors l.jpg

CENS - UCLA

July 25, 2003

Earthquake Sensation:integrating GPS and inertial sensors

Kenneth W. Hudnut, Ph.D.

Chief, So. Calif. Earthquake Hazard Assessment Project

Earthquake Hazards Team

U. S. Geological Survey


Southern california is the nation s most dangerous place for earthquakes why l.jpg

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

Silver linings:

State-of-the-art earthquake monitoring arrays

Many of the world’s best researchers work within this natural laboratory


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San Andreas fault

  • 35 mm/yr slip rate;

    • >70% of total plate boundary motion

    • 1685, 1812, 1857 eq’s

  • Big Bend compression

    • 1971 Sylmar (M 6.7)

    • 1994 Northridge (M 6.7)

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

  • 150+ BB CISN stations

  • 250+ SCIGN stations

  • Catalog; SCEC CMM3


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Improving hazard assessment

  • Temporal variations do occur:

    • Clustering (e.g., Basin & Range, ECSZ, Asia)

    • Discrepant geological and geodetic rates

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

  • Implement robust research findings into hazard assessment

  • “Variability does not mean predictability”

Courtesy Anke Friedrich


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GPS


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SCIGN Data Products

  • 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)


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New methods and data integration

  • Precise topographic mapping of surface ruptures and active fault scarps

    • slip models for prehistoric events

    • rapid assessment of surface slip and damage patterns after large events

    • Requires precise integration of GPS & INS for flight navigation

1957

Gobi-Altai

earthquake

surface

rupture


Hudnut k w usgs a borsa ucsd c glennie aerotec llc and j b minster ucsd l.jpg

High resolution topography along surface rupture of the October 16, 1999 Hector Mine, California Earthquake (Mw7.1) from Airborne Laser Swath Mapping

Hudnut, K. W. (USGS), A. Borsa (UCSD),

C. Glennie (Aerotec, LLC) and J.-B. Minster (UCSD)

Bulletin of the Seismological Society of America

Special 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

Airborne platform navigation

must be highly precise and

requires high-rate GPS data

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


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R

v

v

r

r

R

Geolocation Vectors and Error Sources

Vector from CMearth to GPS phase center

Magnitude & directional errors both are

stochastic, time and location variant.

Vector from GPS phase center to laser

Magnitude error is constant if no airframe

flexing. Directional error due to constant

and time-varying biases in INS.

Vector from laser to ground footprint

Magnitude error due to timing, instrument

and atmospheric delays. Directional error

from constant mirror mounting offsets and

time-varying biases in reporting of scan

angles (both pitch and roll).

Note: additional errors due to imperfect

synchronization of GPS, INS, mirror scan

and laser firing times must be modeled

and removed as well.


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Exploded

ordnance

(crater)

Lavic Lake

Roll & Pitch

Maneuvers

pitch maneuvers


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Maximum

slip

section

of the

1999

Hector

Mine eq.

surface

rupture

Photo by

Keith Stark

(SCIGN)


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Estimating slip on ‘max. slip’ segment ofthe fault


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Laser Scanof the San Andreas

Proposal to the

NSF EarthScope

Science RFP:

Prof. Mike Bevis, PI (OSU)

Requires

high-rate (1 Hz)

GPS data

from SCIGN

sites along

fhe fault &

special care

with IMU-INS


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GPS Fault Slip Sensor

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/

K. Hudnut, G. Anderson, A. Aspiotes,

N. King, R. Moffitt, & K. Stark

(all at USGS-SCIGN, Pasadena CA)


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Central

Computers

Early Warning

The speed of light >> the speed of sound

EmergencyResponse

Seismic

and

GPS

Stations

Utilities

Transport-

ation

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


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Real-Time GPS Network - Enhancing SCIGN

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

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

  • Upgrade SCIGN telemetry

    • DSL, frame relay

    • Radio repeaters, WiGate and dedicated links

    • Data buffering

  • Augment SCIGN real-time acquisition and processing system

    • Implemented sub-daily processing (4 hr) for ~100 SCIGN stations (down from 24 hr)

    • Implementing multiple real-time streaming GPS processors (commercial software)


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Lone 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 results

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 telemetry

Low cost options such as frequent FTS dial-up, radio nets, and DSL

Development & testing of near real-time GPS precise processing, etc.


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Conclusions:

  • GPS and inertial sensor integration for high-accuracy applications is practical in SoCal because SCIGN can be readily upgraded to support centimeter-level accuracy in real-time

  • Earthquake applications of GPS/INS integration are:

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

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


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