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 CENS - UCLA July 25, 2003

2 CENS - UCLA 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

3 CENS - UCLA San Andreas fault 35 mm/yr slip rate;35 mm/yr slip rate; >70% of total plate boundary motion>70% of total plate boundary 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 ‘wired’ (much like Japan & Taiwan)SoCal is now heavily ‘wired’ (much like Japan & Taiwan) 150+ BB CISN stations150+ BB CISN stations 250+ SCIGN stations250+ SCIGN stations Catalog; SCEC CMM3Catalog; SCEC CMM3

4 CENS - UCLA Improving hazard assessment Temporal variations do occur:Temporal variations do occur: Clustering (e.g., Basin & Range, ECSZ, Asia)Clustering (e.g., Basin & Range, ECSZ, Asia) Discrepant geological and geodetic ratesDiscrepant geological and geodetic rates Sequences involving fault interaction (e.g., Joshua Tree - Landers - Big Bear - Hector Mine; Anatolian system, etc.)Sequences involving fault interaction (e.g., Joshua Tree - Landers - Big Bear - Hector Mine; Anatolian system, etc.) Implement robust research findings into hazard assessmentImplement robust research findings into hazard assessment “Variability does not mean predictability”“Variability does not mean predictability” Courtesy Anke Friedrich

5 CENS - UCLA GPS

6 CENS - UCLA 1 st Year Combined time series ( ) 3 rd Year Real-time earth- quake response 5 th Year Resolve rates on primary LA basin faults (and others) SCIGN Data Products

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8 CENS - UCLA New methods and data integration Precise topographic mapping of surface ruptures and active fault scarpsPrecise topographic mapping of surface ruptures and active fault scarps slip models for prehistoric eventsslip models for prehistoric events rapid assessment of surface slip and damage patterns after large eventsrapid assessment of surface slip and damage patterns after large events Requires precise integration of GPS & INS for flight navigationRequires precise integration of GPS & INS for flight navigation 1957 Gobi-Altai earthquake surface rupture

High resolution topography along surface rupture of the October 16, 1999 Hector Mine, California Earthquake (M w 7.1) 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)

10 CENS - UCLA 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 navigation must be highly precise and requires high-rate GPS data

11 CENS - UCLA R r v Geolocation Vectors and Error Sources r Vector from CM earth to GPS phase center Magnitude & directional errors both are stochastic, time and location variant. R v 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.

12 CENS - UCLA Lavic Lake Roll & Pitch Maneuvers Exploded ordnance (crater) pitch maneuvers

13 CENS - UCLA Photo by Keith Stark (SCIGN) Maximum slip section of the 1999 Hector Mine eq. surface rupture

14 CENS - UCLA Estimating slip on ‘max. slip’ segment of the fault

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19 CENS - UCLA Laser Scan of 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

GPS Fault Slip Sensor K. Hudnut, G. Anderson, A. Aspiotes, N. King, R. Moffitt, & K. Stark (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

21 CENS - UCLA Early Warning The speed of light >> the speed of sound Seismic and GPS Stations Central Computers Utilities Emergency Response Transport- ation (e.g; Wu & Teng, BSSA, 2002; Allen & Kanamori, Science, 2003)

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23 CENS - UCLA Real-Time GPS Network - Enhancing SCIGN On 15 November 2002, first-ever GPS fault slip sensor deployed across San Andreas fault at Gorman, Calif. 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 Augments seismic early warning system - resolves the observational deficiency inherent with inertial sensors that cannot discern tilt from acceleration Upgrade SCIGN telemetry Upgrade SCIGN telemetry DSL, frame relay DSL, frame relay Radio repeaters, WiGate and dedicated links Radio repeaters, WiGate and dedicated links Data buffering Data buffering Augment SCIGN real-time acquisition and processing system Augment SCIGN real-time acquisition and processing system Implemented sub-daily processing (4 hr) for ~100 SCIGN stations (down from 24 hr) Implemented sub-daily processing (4 hr) for ~100 SCIGN stations (down from 24 hr) Implementing multiple real-time streaming GPS processors (commercial software) Implementing multiple real-time streaming GPS processors (commercial software)

24 CENS - UCLA Lone Juniper Ranch and Frazier Park High School First prototype GPS fault slip sensor Spans the San Andreas fault near Gorman, California

25 CENS - UCLA 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?

26 CENS - UCLA 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.

27 CENS - UCLA 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-timeGPS 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: Earthquake applications of GPS/INS integration are: societally relevant - significant economic impact and consequences would result from technological innovations 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 scientifically exciting for the very dynamic SCEC research community - major breakthroughs in earthquake source physics are likely to result from collaborations