Integrating GPS with rotational and inertial sensors Early Warning & DamageMap
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Integrating GPS with rotationaland inertial sensorsEarly Warning & DamageMap
Kenneth W. Hudnut, Ph.D.
Geophysicist
USGS, Pasadena
Measuring the Rotation Effects
of Strong Ground Motion
USGS, Pasadena
16 February 2006
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San Andreas fault 35 mm/yr slip rate;
>70% of plate motion 1685, 1857 eq’s
SoCal is now well ‘wired’
Likely source of most future ‘Big Ones’
Fault physics experiment GPS/INS in near-field ALSM & DG scan ‘net’
Great place to test EEW
Build “zipper” arrays Cholame - Simmler Coachella Valley
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GPS network infra-structure forms afoundation for real-timestructural damagedetection and response
• Telemetry upgrades• Algorithm develop-
ment and testing• Implementation
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Sensor technology
Frequency response
positiondisplacement velocity acceleration
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Proper transducers for the EEW job:borehole strain, tilt, strong motion, GPS, gyros?
Courtesyof JohnLangbein(USGS)
Gyros
Langbein & Bock (2003)
GPS
Gyros
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GPS/INS (RLG) inairborne imaging: GPS aircraft trajectory
relative to ground-based GPS array
INS (gyro) for aircraft attitude
Laser mirror and/or camera position and orientation very well known
New imaging capabilities (also for satellite imagery)
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Sagnac Interferometer
RLG’s&
FOG’s
Designedto sleep
for decadesthen wakeup quickly
and performflawlessly for
several minutes
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Gyros and MEMS with GPS• Stable gyro technology is costly but MEMS-gyro
and FOG are lower cost and approaching accuracy
Barbour & Schmidt, 1998
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San Andreas - place two betsboth ~120 km from Los Angeles (LA)
Coachella Valleysegment is ~60 kmto San Bernardino
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Lone Juniper Ranch and Frazier Park High School
Prototype GPS fault slip sensor; up to 10 Hz
Spans the San Andreas fault near Gorman, California
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GPS high-rate (1 Hz) analysis
• Larson, Billich and Choi - see Ji et al.– Sidereal filtering
(Larson, Choi)
– Stacking (Billich)
• Significant reduction in long-period drift
• Compares well now with our static GPS displacements
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Doubly-integrated seismic vs. GPS for Parkfield 2004 (co-located @ PHOB)
Raw GPS solution in blueFiltered GPS in greenSeismic in red (Boore)
These show results prior tofinal GPS analysis step ofstacking, shown previously
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Simplifying assumptions…
Sensor technology exists: Inertial
BB seismic, accelerometers, gyros
GPS - will keep improving
Telemetry technology exists
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San Andreas - instrument majorlifeline infrastructure crossings
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•Satellite
•Telemetry
•Internet
SENSOR PACKAGE
-Accelerometer-Tiltmeter-GPS sensor
REAL-TIME DAMAGE ASSESSMENT
Courtesy ofErdal Safak (USGS)
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Factor Building at UCLAPrototype for DamageMap
PI’s Erdal Safak, Monical Kohler and Paul Davis
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Initial GPS Data from Factor Building
Y RMSE = 5 cmX RMSE = 9 cm
100 times better than normal GPS accuracy (SPS now near PPS performance of 6-20 m @ 95% w/ S/A off)
Available worldwide $1400/yr.
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Summary
Future earthquake monitoring systems will allow faster and better response
Tools support rapid and accurate decision-making by emergency responders Fault Slip Sensor and DamageMap concepts Measure fault slip or structural damage directly - don’t need to know anything
else - ‘quick & easy’ and simple, robust reliable design obtain more accurate displacement observations, esp. at lifeline fault crossings new instrumentation for dynamic and static displacement address deficiencies
due to double-integration of accelerometer records
Same R&D effort as for DamageMap instrumentation - now under way with USGS Venture Capital and ANSS start-up funds, but major funding and long-term support for implementation has not yet been identified
We are far from being prepared for a Big One in California - it is time to “step it up” - use new technology, fix problems ahead of time
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Ken Hudnut
Dept. of the Interior - U. S. Geological Survey
525 South Wilson Ave.
Pasadena, CA 91106
626-583-7232