HR: 08:05h
AN: S51E-01 INVITED     [Abstracts]
TI: IRIS Controlled Source Seismic Experiments: Continental Structure, Instrumentation, and Education
AU: * Mooney, W D
EM: mooney@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd. MS 977, Menlo Park, CA 94025 United States
AU: Keller, G R
EM: keller@utep.edu
AF: University of Texas at El Paso, Dept. of Geological Sciences, El Paso, TX 79968 United States
AB: The controlled-source seismology program of IRIS/PASSCAL has made major contributions to the study of continental structure and evolution. It has also undergone major developments in seismic instrumentation. The first PASSCAL experiments (1984/85) targeted the Basin and Range Province and the Ouachita orogenic belt. The Basin and Range study provided remarkably clear images of this thin, highly-extended crust, while the Ouachita experiment tested competing hypotheses for the deep structure of this Paleozoic orogen. However, both of these projects were limited by a lack of seismic instruments. The situation improved in the late 1980's with the benefit of a mixed array of 600 seismic recorders from the USGS, Stanford, and the Geological Survey of Canada. The resolution achieved with these instruments was revolutionary. Results include the imaging of such remarkable features as crustal-scale duplexes in the Brooks Range compressional orogen of northern Alaska, and of crustal "core complexes" in the extended crust of southwest Arizona. The 3-channel PASSCAL Jr. instrument was developed, leading to experiments in which $\sim$1000 instruments were deployed, including three-component recording. This complex mix of instruments served the community well for several years, but required large, complex instrument centers and lots of technical support. With input from PASSCAL and the international community, a newly designed, compact instrument (the Texan) was finalized in the spring of 1998, and the first 200 instruments was delivered to the Univ. of Texas-El Paso in late 1998. The present instrument pool of Texans exceeds 1,400 and these have been used on such projects as the high-resolution imaging of the Los Angeles and San Fernando basins (LARSE I and II experiments), where active thrust faults have been imaged. Controlled-source seismic experiments are now very numerous. During calendar year 2004 alone, portable Texan instruments have traveled from Venezuela to Denmark, Romania, Hungary, Nevada, Chesapeake Bay (VA.), the Dead Sea rift, and back to Venezuela. The scientific targets of these experiments range in scale from shallow environmental depths to the entire lithosphere. In this talk we highlight many of the key scientific achievements of IRIS/PASSCAL controlled source experiments, with an emphasis on new insights into the structure, composition, and evolution of the continental crust. We also briefly describe the experiences of the hundreds of students who have participated in past field work. Many of these students are now pursuing active careers in seismology and are using the PASSCAL facility as young professionals.
DE: 7255 Surface waves and free oscillations
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 7205 Continental crust (1242)
DE: 7207 Core and mantle
DE: 3900 MINERAL PHYSICS
SC: Seismology [S]
MN: 2004 AGU Fall Meeting