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

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

GPS network infra-structure forms afoundation for real-timestructural damagedetection and response

• Telemetry upgrades• Algorithm develop-

ment and testing• Implementation

Sensor technology

Frequency response

positiondisplacement velocity acceleration

Proper transducers for the EEW job:borehole strain, tilt, strong motion, GPS, gyros?

Courtesyof JohnLangbein(USGS)

Gyros

Langbein & Bock (2003)

GPS

Gyros

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)

Sagnac Interferometer

RLG’s&

FOG’s

Designedto sleep

for decadesthen wakeup quickly

and performflawlessly for

several minutes

Gyros and MEMS with GPS• Stable gyro technology is costly but MEMS-gyro

and FOG are lower cost and approaching accuracy

Barbour & Schmidt, 1998

San Andreas - place two betsboth ~120 km from Los Angeles (LA)

Coachella Valleysegment is ~60 kmto San Bernardino

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

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

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

Simplifying assumptions…

Sensor technology exists: Inertial

BB seismic, accelerometers, gyros

GPS - will keep improving

Telemetry technology exists

San Andreas - instrument majorlifeline infrastructure crossings

•Satellite

•Telemetry

•Internet

SENSOR PACKAGE

-Accelerometer-Tiltmeter-GPS sensor

REAL-TIME DAMAGE ASSESSMENT

Courtesy ofErdal Safak (USGS)

Factor Building at UCLAPrototype for DamageMap

PI’s Erdal Safak, Monical Kohler and Paul Davis

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.

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

Ken Hudnut

Dept. of the Interior - U. S. Geological Survey

525 South Wilson Ave.

Pasadena, CA 91106

626-583-7232

hudnut@usgs.gov