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September 4, 2015
3:00pm in PLS 1140
Wenjie Jiao
Microseismic Studies for Unconventional Reservoirs
September 11, 2015
3:00pm in PLS 1140
Melodie French from University of Maryland
Creep and the potential for seismicity along the central segment of the San Andreas Fault

Abstract: The central segment of the San Andreas Fault (SAF) currently accommodates displacement by a combination of aseismic creep and microseismicity. In the past, earthquakes on the adjacent locked segments of the SAF have arrested at the boundaries of the creeping segment, indicating that it is a barrier to rupture propagation. Although historically aseismic, we still do not know whether a sufficiently large rupture could initiate on a locked segment and propagate into and through the creeping segment of the SAF.

The San Andreas Fault Observatory at Depth (SAFOD) program recovered fault rock from two clay-rich gouge zones at 2.7 km depth along the creeping segment of the SAF, near its boundary with the southern locked segment. The Southwest Deforming Zone (SDZ) and Central Deforming Zone (CDZ) are cumulatively four meters thick and are believed to accommodate most of the plate boundary displacement at SAFOD. I present results from deformation experiments conducted on gouge from the CDZ at shear rates that range from in-situ creep to seismic slip. The strength of the gouge varies with shear rate and this strength variation reflects an evolution in deformation processes that is recorded in the microstructure of the sheared gouge. I will discuss how the mechanical and microstructural properties are critical to constraining the potential for seismic slip along the creeping segment of the SAF. Finally, I will discuss how results from the SAFOD community have revealed the long-term evolution and seismic cycles of creeping plate boundary faults.

September 18, 2015
3:00pm in PLS 1140
Bruce Buffett from University of California, Berkeley
Geomagnetic reversals and excursions: Insights into the origins of Earth's magnetic field

Abstract: Palaeomagnetic observations offer important insights into the origin of Earth's interior, but a detailed reconstruction of the underlying dynamics is not feasible. A practical alternative is to construct a stochastic model for the time evolution of the dipole field. Slow changes in the field are described by a deterministic (drift) term, whereas short-time fluctuations are represented by a random (noise) term. Estimates for the drift and noise terms can be recovered from a time series of variations in the axial dipole moment over the past 2 million years. The results are used to predict a number of statistical properties of the palaeomagnetic field, including the average rates of magnetic reversals and excursions. A physical interpretation of the stochastic models suggests that reversals and excursions are part of a continuum of time variations in Earth's magnetic field, arising from convective fluctuations in the core. Relatively modest changes the amplitude of convective fluctuations can produce large changes in reversal rates, including the well-known occurrence of superchrons lasting longer than 10 million years.

October 2, 2015
3:00pm in PLS 1140
Phil Candela from University of Maryland, College Park
October 16, 2015
3:00pm in PLS 1140
Kanani Lee from Yale University
October 30, 2015
3:00pm in PLS 1140
Mary Anne Holmes from Univ. Nebraska and NSF
November 6, 2015
3:00pm in PLS 1140
Diana Roman from Carnegie - DTM
November 13, 2015
3:00pm in PLS 1140
Jessica Irving from Princeton University
December 4, 2015
3:00pm in PLS 1140
Marcia McNutt from American Association for the Advancement of Science
Geoscience Problem Solving for Sustainability: Focus on Climate and Energy

Abstract: Geoscientists are and will continue to be at the forefront of finding solutions to many of the world¹s most pressing challenges for how to find solutions to many of problems in maintaining and enhancing the quality of life for the billions of people on Earth in a sustainable manner. At the center of this challenge is the energy-climate change nexus: how to provide abundant energy to power modern society without continuing to contribute to the risk of climate change. Geoscientists are solving these problems by helping to find energy sources with lower CO2 emissions, providing the science for climate change adaptation, and exploring the prospects for climate intervention. Hand-in-hand with these issues, geoscientists need to be cognizant of the continuing need for abundant critical materials and water for alternative energy technologies and energy production.

The coordinator for the Colloquium Series is Dr. Vedran Lekic. You can contact him at