Examples of Integrated Geophysical Projects
The LITHOPROBE Experience: Active-source Seismology and Other Earth Science – An Essential Combination for Understanding Tectonic Evolution
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The primary points that I want to make with respect to EarthScope in the Northern Rockies are:
- For most geologists to participate meaningfully in the EarthScope program, multichannel reflection and refraction/wide-angle reflection seismology must be part of the scientific program
- The active-source seismology program must be directed at geological targets that have fundamental significance for understanding tectonic evolution
- The active-source seismology program must be coordinated with geological studies and Flexible Array
One of the issues within EarthScope might be: "How do we determine the geological targets that have fundamental significance for understanding tectonic evolution?". While I don't believe there is necessarily only one approach to address this question, that taken by LITHOPROBE is the following.
- Call for integrated, multidisciplinary proposals from a New Transects Subcommittee
- Peer-review nationally and internationally
- Internal review by 3 disciplinary subcommittees [seismic, em, geology] and the senior Scientific Committee
- Review of evaluations by New Transects Subcommittee
- Recommendation to Scientific Committee and LITHOPROBE Board of Directors
Within LITHOPROBE there are many examples that demonstrate the primary points noted above. In this presentation, I will focus on results from LITHOPROBE's Trans-Hudson Orogen (THO) and Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) transects. The THO is the world's largest and best exposed Paleoproterozoic orogen. It comprises suites of juvenile rocks and reworked Archean rocks that stitched together the Archean Hearne-Rae, Sask and likely Wyoming cratons to the west with the Archean Superior craton to the east. The SNORCLE Transect examines tectonic features from the small Archean Slave craton in the Northwest Territories westward through the Paleoproterozoic Wopmay Orogen and into the Cordillera of northern Canada. It represents the only region on Earth where 4 Ga of Earth history can be examined in one large area. In this presentation, I will exemplify results only from the Precambrian regions.
Jim Ni, Dave Wilson, Wei Gao, Steve Grand, W. Scott Baldridge, Steve Semken and Michael West
Rick Aster, New Mexico Tech
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Breakout A: Extensional tectonics on the largest scale. Why does the Sierra Nevada block move? What is the cause of Great Basin uplift? Present high elevation? What aspects of lithospheric rheology control Great Basin strength and deformation? What made the rheology as it is?
Breakout B: Rheology of the Mantle and its Relation to Current Tectonics; Why Are Some Parts of the Basin and Range More Active than Others? What does Great Basin deformation say about lithospheric rheology? The role of fluids: Can magnetotellurics reduce non-uniqueness of mantle seismic models?
Breakout C: What is the mantle and lower crust in the Great Basin doing now? What are the relevant mantle processes? How are the crust and mantle coupled?
Breakout D: Contrasts between the Eastern and Western Great Basin. What are the geophysical similarities and differences between east and west? Where is the boundary between the Proterozoic basement that underlies the E B&R and the Paleozoic/Mesozoic accreted terrain beneath the west? What drives seismicity east of the Wasatch Front?
Breakout E: How do faults behave over time? Do they turn on and off, speed up—slow down? If so, why? Where are the discrepancies between geodetic, geologic, and seismic rates of strain accumulation? Geological study and dating and mapping facilities were recognized as necessary.
Breakout F: Relations of Economic Resources to Tectonics (Structure, Magmatism, Fluid and Heat Flow) What are the large-scale controls on Eocene mineralization - Carlin Au (NNW trending) and porphyry Cu-Au-Mo (EW trending)? Industry collaborations could be mutually beneficial.
Breakout G: Walker Lane. When did it start? How does the crust accommodate simultaneous extension and strike-slip deformation in the Walker Lane?
Breakout H: Seismic and Geophysical Methods, Crust and Mantle. Three projects in sub-disciplinary self-organization were identified: (1) Promote the use of legacy data and models. (2) Develop a test site or proving ground. (3) Develop a community modeling environment (CME). Tom Jordan, drawing on successful experience with the Southern California Earthquake Center (SCEC), presented points recognized by the organizing committee as important for successful EarthScope efforts in the Great Basin: (1) Problem focus. (2) Common objectives. (3) Community data products and models. (3) Community identity and organization. (4) Collaboratory infrastructure to provide code validation, standardization of products. (5) Regular forums for assessing progress including workshops and annual meetings. (6) Funding to support collaboration/collaboratory activities.
GreatBREAK was held June 21-23, 2004 in Tahoe City, California. Powerpoint presentations and the complete workshop report are available on the web at www.seismo.unr.edu/greatbreak.
*John Anderson (Chair), Glenn Biasi, John Louie, Steve Wesnousky, University of Nevada, Reno
Rick Aster, New Mexico Tech
Geoff Blewitt, James Faulds, Jon Price, Nevada Bureau of Mines and Geology
Lew Gustafson, Independent Consultant
Gene Humphreys, University of Oregon
Phil Wannamaker, University of Utah
download PowerPoint presentation (PowerPoint 3.8MB Oct24 05)
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