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Spring 2016 Colloquia

January 18: Martin Luther King Day, no colloquium.

January 20: cancelled due to weather. David Bromwich, Ohio State University Atmospheric Sciences Program, Department of Geography. Title: Climate change in West Antarctica: Are we heading for a dramatic rise in sea level?

January 25: Doug Jerolmack, University of Pennsylvania Department of Earth and Environmental Sciences. Title: Creepy Landscapes (or, why the threshold of sediment transport is everything, and determining it is impossible).

February 1: Hydrology/Surface Processes Candidate talk Title: TBA

February 8: Heather DeShon, Southern Methodist University and Earthscope. Title: Death of a fault: a comparison of seismicity in the New Madrid Seismic Zone and North Texas

Abstract: Increased seismicity rates across the central United States have raised scientific questions and local and national concerns about the impact of shale gas production on infrastructure and subsurface structures such as faults. But the central US is not historically aseismic and intraplate faulting is not uncommon. This talk explores similarities and differences between the intraplate New Madrid seismic zone, host to the large (M7+) earthquakes of 1811-1812 and focus of the Earthscope NELE experiment, and ongoing earthquake sequences occurring in the Fort Worth (Barnett Shale) Basin. Both New Madrid seismicity and North Texas earthquakes occur along reactivated ancient faults located in the basement granites and overlying sedimentary units and release natural tectonic stresses. New Madrid has a long paleoseismic record of large earthquakes. In contrast, North Texas had no credible felt earthquakes prior to 2008 and the recent swarms have been linked to local wastewater injection associated with shale gas extraction (2008/2009 DFW; 2009 Cleburne; 2013 Azle); studies of the 2014/2015 Irving-Dallas and 2015 Venus sequences are ongoing. Both regions are currently monitored – New Madrid by the USGS and CERI permanent network and Earthscope stations and North Texas by a ~40 station temporary network operated by SMU with support from the USGS. High-resolution earthquake locations, waveform correlation, and source characteristics are combined with information on subsurface geology and fault structure, and 3D pore pressure modeling to provide insight into the relationship between fluid migration at depth and modern microseismicity along pre-existing fault structures. Understanding if and/or how injection of fluids into the crystalline crust reactivates faults have important implications for seismology (i.e., fault physics), the energy industry, and society. Comparisons of potentially induced sequences like North Texas with natural intraplate seismic zones like New Madrid may yield important insights to understanding the long-term hazard associated with the increased seismicity in the Central US.

Tuesday March 8: Brown Bag seminar Title: TBA

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March 14: No Colloquium, Spring Break

March 21: Jisou Jin, University of Western Ontario. Title: Mass extinction of continental-sized Late Ordovician "island fauna" in North America.

March 28: Emily Finzel, University of Iowa. Title: Provenance and Exhumation Response to Different Subduction Modes, Southern Alaska

April 4: Catherine Macris, IUPUI. Title: Seconds after Impact: Insights from Tektites and Experiments

Abstract: Tektites are natural glasses formed as a result of melting and quenching of distally ejected terrestrial material upon hypervelocity (>11 km/s) impact on Earth. Some tektites contain inclusions of lechatelierite (nearly pure SiO2 glass; 99-100 wt.% SiO2), thought to be the amorphous relicts of partially digested quartz grains. This study exploits the presence of these local heterogeneities to extract information about tektite thermal histories by investigating chemical diffusion between molten silica inclusions and surrounding peraluminous felsic melt in natural tektites and experimental analogues.

April 11: TUDOR LECTURE John Shaw, Harvard University. Title: Deformation in active thrust sheets through multiple earthquake cycles

Abstract: Active thrust faults pose significant earthquake hazards in the western United States and in many other convergent plate boundaries around the world. Traditional paleoseismic methods for assessing such hazards have relied primarily on fault offsets of stratigraphic horizons and/or geomorphic markers. However, recent events, such as the 1999 Chi Chi (M 7.6), Taiwan, 2008 Wenchuan (M 7.9), China, and 2015 Gorkha (M 7.8), Nepal earthquakes demonstrate the complex nature of thrust fault ruptures, which often exhibit significant components of coseismic folding, in addition to faulting. Indeed, many active thrust faults – or portions of faults – are blind, such that deformation at the Earth’s surface is characterized exclusively by folding. We will explore a series of active thrust sheets in California and the Junggar basin, China, that are constrained by fault scarps, folded marine and fluvial terraces, and subsurface geophysical data. These examples highlight how fault slip and seismic moment release at depth are partitioned into components of folding and faulting in the shallow subsurface. This, in turn, provides methods for using surface deformation patterns such as folding to infer fault behavior at depth for improved seismic hazard assessments.

April 18: Amy Townsend, University of Cincinnati. Title: Isotopic constraints on methane emissions from natural gas production: Will fugitive methane emissions overwhelm the climate benefits of a natural gas energy future?

Abstract: Methane is a powerful greenhouse gas and the dominant component of natural gas. Combustion of natural gas releases less carbon dioxide per unit of energy returned than coal or oil, but increasing natural gas production may lead to increases in methane emissions, which could overwhelm the climate benefits of a switch from coal to gas. But measurement of methane emissions from natural gas systems is complicated by the many other anthropogenic and natural sources of methane. My work explores the use of stable isotopes as source apportionment tracers of natural gas versus other methane sources.

Last month Amy published the following paper: Emissions of coalbed and natural gas methane from abandoned oil and gas wells in the United States (Geophysical Research Letters 43 (5), 2283-2290; link to paper).

April 25: Becky Lange, University of Michigan, Ann Arbor. Title: "The origin of voluminous, highly differentiated rhyolites, the most evolved magmas on Earth, and the resolution of several paradoxes.

May 2: No Colloquium, Final Exam Week