Fall 2016

Tuesday Afternoons at 3:30 PM

Thim Lecture 001

September 27, 2016

Speaker: Tess Weathers, UCSC

Title: Perfluoroalkyl acids and microorganisms: Implications for groundwater transport and microbial processes

Hosts: Cara Vennari

October 4, 2016

Speaker: Travis O'Brien, Lawrence Berkeley National Laboratory

Title:  A Case for Missing Physics in Climate Models

Hosts: JP O'Brien

October 11, 2016

Speaker: Steve Constable, UC San Diego

Title: Marine EM: The Past, The Present, and The Future

Abstract: The high cost of deepwater exploration motivated the development of commercial marine magnetotelluric (MT) exploration in 1995, but it wasn’t until marine controlledsource electromagnetic (CSEM) methods burst upon the industry scene with the formation of three new contractors in 2002 that things got really exciting. Now the bubble has burst and the excitement has diminished, but marine EM remains an important tool for offshore exploration. Early mistakes were made as a result of poor instrumentation and a lack of good interpretation tools unlike seismics, EM relies heavily on inversion to produce useful results but both equipment and inversion codes have improved significantly. Still, EM images resistivity, not hydrocarbon content, and false positives occasionally occur, but false negatives are rare. That is, without an EM signature there is little chance of discovering economical hydrocarbons. In this lecture I will review the history, discuss the 10 important things you need to know about marine EM, and look to the future of the method.

Hosts: Ana Martinez Fernandez

October 18, 2016

Speaker: Zanna Chase, University of Tasmania, Australia

Title: Opal production and flux in the Southern Ocean: Past and present

Hosts: Michele Markowitz

October 25, 2016

Speaker: Ted Biddy, UC Santa Barbara

Title: Landscape evolution and the preservation of ancient ice in Ong Valley, Antarctica

Hosts: Grace Barcheck

October 27, 2016

Special Seminar in E&MS A340 from 3:00-4:30PM

Speaker: Dan Killam, Michele Markowitz and Karen Petersen, UCSC

Title: International Research Experience for Students in Coastal Zone Research (IRES) 2016

Hosts: Adina Paytan

November 1, 2016

Speaker: Michal Kopera, UCSC

Title: Title: A new computational approach to modeling of ice-sheet / ocean interactions in Greenland’s Fjords

Abstract: Ice-sheet/ocean interaction in narrow fjords around Greenland is one of the key outstanding challenges in modeling studies of climate change and sea level rise. The runoff from Greenland's ice-sheet (GiS) is a significant factor in the regional ocean dynamics and global sea-level rise, yet present-day climate models are not able to resolve fine-scale processes in the fjords without prohibitive computational costs. This is due to orders of magnitude difference of spatial scales between the open ocean (~1000km) and fjord (<1km) as well as complicated bathymetry and coastline between the ocean outside fjord and a marine-terminating glacier.

I will be presenting objectives and progress of the NUMO project (Non-hydrostatic Unified Model of the Atmosphere). The goal of the NUMO project is to develop a non-hydrostatic ocean model with an unstructured grid and local non-conforming mesh refinement, able to resolve fine scale ice-sheet / ocean interactions, the 3-dimensional circulation within Greenland fjords and exchanges with the ocean outside. As a proof-of-concept, we focus on Sermilik Fjord and its interaction with Helheim glacier and the sub-polar North Atlantic Ocean. The fine scale and most critical processes at an ice-sheet / ocean interface are modeled using a high-resolution, locally refined mesh. An unstructured mesh is used to realistically represent the geometry of the fjord, while in the areas of particular importance (i.e. glacier front) the resolution is increased by non-conforming mesh refinement. This approach allows us to transition between coarse and fine mesh quickly and robustly, ensuring relatively small overall computational cost of the simulation. Boundary conditions are prescribed from observations and passed to the model via CPL7 coupler. The model is designed such that it can be easily coupled with existing Earth System Models (ESMs) through a flux coupler. The long-term goal is to simulate all Greenland’s fjords and adjacent coastal ocean and couple this simulation to a regional or global ESM.

Hosts: Neil Foley

November 8, 2016

Speaker: Nicolas Barth, UC Riverside

Title: Tectono-geomorphic perspectives on the Alpine Fault, New Zealand

Abstract: This talk will encompass recent efforts to improve the understanding of California's sister plate boundary, the active continental strike-slip Alpine Fault in New Zealand. Topics covered include characterizing fault rocks to understand earthquake behavior, utilizing lidar data to reveal surface rupture distribution and slip partitioning, exploiting a unique regional 8km strike-slip offset to determine high-precision fault slip rates, and assessing the role very large landslides play on Alpine Fault seismic hazard. Together these studies paint a view of the Alpine Fault as a highly-localized, long-lived, very weak locus of plate boundary motion that has had relatively constant spatio-temporal displacement rates in the latter part of its history, ruptures in hazardous large-magnitude earthquakes with considerable coseismic geomorphic effects, and exerts a first-order control on landscape evolution of the South Island. Throughout the talk I will draw on comparisons to the San Andreas Fault System, highlighting what the comparatively simple Alpine Fault can possibly tell us about our messy, complex world in California.

Hosts: Alex Nereson

November 15, 2016

Speaker:Jeffrey Moore, NASA

Title: Geology of the Pluto System

Hosts: Nick Zube

November 22, 2016

Speaker:David Stevenson, CalTech

Title: The Connection between Planetary Magnetic Fields and Planetary Formation

Hosts:Jack Conrad

November 29, 2016

Speaker: John Wakabayashi, CSU Fresno

Title: Subduction Channel NOT: Strain Localization and Megathrust Slip Accommodation Modes in the Franciscan Complex, California

Abstract: Numerical models of subduction produce broad (multi-km thickness) zones of displacement that accommodate subduction megathrust displacement and exhumation of subduction complex rocks.   Such displacement zones are commonly referred to as a “subduction channels”.  Many assert that mélanges represent the exhumed analogs of such channels, and that subduction slip and exhumation results in tectonic mixing of the blocks in matrix.  Field relationships in the Franciscan Complex of California contradict such models. Franciscan mélanges with exotic blocks that have been considered type examples of exhumed subduction channels show evidence for incorporation of blocks by sedimentary sliding prior to burial and subsequent tectonic deformation. These mélanges are commonly less than 1 km in thickness and are variably deformed sedimentary packages rather than shear zones.  In contrast, more limited (tens of meters thick) fault zones show progressive deformation from imbricated ocean plate stratigraphy to block-in-matrix geometry; such zones lack exotic blocks.  Megathrust slip appears to have been accommodated in two modes, accretionary and non accretionary.  For the accretionary mode a series of faults accommodated the transfer of the unit from the subducting to the upper plate.  Whereas the megathrust slip in such cases is accommodated on faults spanning the full structural thickness of the unit (several km), most of the rock shows little if any penetrative strain. The faults accommodating the accretion range from cm-scale brittle fault zones to networks of brittle faults that may collectively span tens of meters.  Non-accretionary megathrust zones may have accommodated most of the ~13000 km of Franciscan subduction slip.  Such zones separate accreted units with notable contrasts in lithology and have a thickness of  <50 m.  Most of the exhumation of Franciscan rocks was accommodated by upper plate extension, and cross-sectional extrusion (thrust fault below, normal fault above).  Faults accommodating exhumation appear to have been discrete features of minimal thickness (also tens of meters or thinner).  This is consistent with sharp contrasts in metamorphic grade across narrow (10s of m and thinner) faults instead of broader metamorphic gradients.

Hosts: Ben Dejarnatt