Earthquake Sensation: Integrating GPS and Intertial Sensors

Title: Earthquake Sensation: Integrating GPS and Intertial Sensors
Invited Speaker: Kenneth W Hudnut, Caltech
Date: FRIDAY, July 25th, 2003
Time: 1pm-2pm
Venue: Room # 4760, Boelter Hall, UCLA
http://www.cens.ucla.edu/seminars/seminar_summer03.html

FOR TELE-ATTENDEES: If you are attending remotely, you may wish to access the
slides at: http://www.cens.ucla.edu/censweb/CENS-Seminar-Series/ (Slides
will be available a few minutes before seminar starts.)

Abstract:

To improve our understanding of earthquake physics, we must make observations of parameters that determine friction on the fault surface during rupture. Observables may include, for example, 3D point trajectories to fully record near-field dynamic phenomena such as slip pulses, as well as details of slip variation along strike. We have devised and tested new methods for observing these quantities in nature - both new methods require highly accurate results from integrated GPS and inertial sensors. First, we observed the details of topography along the 1999 Hector Mine surface rupture using airborne laser swath mapping. This allowed us to estimate slip variation along strike with higher spatial resolution than has ever before been possible. Evidently, slip variations along strike are greater than previously recognized, implying extreme slip heterogeneity. We provide a simple explanation for how such rapid slip variations could provide the source for high-frequency seismically radiated energy, at least in the near field. Second, we have developed the concept for, and built a working prototype of, a GPS Fault Slip Sensor spanning the San Andreas fault. In addition to augmenting seismic early warning systems, such instrumentation could also provide unique records of near-field ground motions. Inertial sensors such as seismic instruments are not able to differ between a tilt and an acceleration, whereas GPS measurements can differentiate these, and can be made with respect to an absolute frame of reference. Other practical limitations exist, however, in both kinds of instrumentation and we will describe how they may best be integrated into a system that will achieve both the scientific observational objectives and support earthquake early warning. The Southern California Integrated GPS Network (SCIGN) is now operational and provides basic infrastructure for such applications. SCIGN has an open data policy, and is seeking partnerships that would allow upgrades to the telemetry system in order to support high-accuracy real-time positioning applications of all kinds.

Biographical Information:

Dr. Hudnut studies southern California's earthquakes, using the Global Positioning System (GPS), at the USGS Pasadena Office, where he is Chief of the Southern California Earthquake Hazard Assessment project, and a Visiting Associate in Geophysics on the Caltech faculty. In 1989, he received his Ph.D. from Columbia University in New York, and in 1983 he received his Bachelor's degree from Dartmouth College in New Hampshire. He has written or co-authored over 60 scientific articles, including the subjects of fault interaction & earthquake triggering, and of crustal deformation associated with recent earthquakes in southern California.