Integrating GPS with rotational and inertial sensors Early 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 a foundation for real-time structural damage detection and response Telemetry upgrades Algorithm develop- ment and testing Implementation

Sensor technology Frequency response position displacement velocity acceleration

Proper transducers for the EEW job: borehole strain, tilt, strong motion, GPS, gyros? Courtesy of John Langbein (USGS) Gyros Langbein & Bock (2003) GPS Gyros

GPS/INS (RLG) in airborne 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 Designed to sleep for decades then wake up quickly and perform flawlessly 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 bets both ~120 km from Los Angeles (LA) Coachella Valley segment is ~60 km to 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 PHOB) Raw GPS solution in blue Filtered GPS in green Seismic in red (Boore) These show results prior to final GPS analysis step of stacking, shown previously

Simplifying assumptions…  Sensor technology exists:  Inertial  BB seismic, accelerometers, gyros  GPS - will keep improving  Telemetry technology exists

San Andreas - instrument major lifeline infrastructure crossings

Courtesy of Erdal Safak (USGS)

Factor Building at UCLA Prototype for DamageMap PI’s Erdal Safak, Monical Kohler and Paul Davis

Initial GPS Data from Factor Building Y RMSE = 5 cm X RMSE = 9 cm 100 times better than normal GPS accuracy (SPS now near PPS performance of % 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