Kim Welford

Investigating Precambrian sills in the crystalline crust of Alberta, Canada...3-D seismic reflection

Woods Hole Oceanographic Institute (WHOI)
Host: R. Snieder

Gerard Schuster

Nancy Glenn

Jessica Schwark
Eugenia Rojas
Dave Balogh

Gerald Bawden

Ingrid Johanson
GP Day Speaker

Active Tectonics Group
University of California, Berkeley

Neil Dannemiller
Michael Ewing
Kjetil 'KJ' Jansen

GP581/681-- Grad
Student Presentations

J. Kim Welford
Postdoctoral Fellow
Department of Earth and Ocean Sciences
University of British Columbia
Thursday, January 13, 2005

Abstract
While 3-D seismic reflection surveying has become the dominant tool for oil and gas exploration within shallow sedimentary strata, crustal-scale tectonic investigations in academic projects (such as Canada's Lithoprobe project and the older U.S. COCORP effort) have focused on the generation of cross-sectional images of the crust from 2-D seismic reflection profiling. However, 3-D techniques have rarely been used for such studies. In a pioneering effort in Canada to examine upper-middle crustal structure to depths of 15 km using 3-D seismic reflection techniques, a deep 3-D reflection dataset collected by the Canadian petroleum industry in northwestern Alberta is used to investigate the Winagami Precambrian plutonic sill complex within the crystalline upper crust, previously identified on Lithoprobe 2-D multichannel reflection lines. The goals of the investigation are to determine the 3-D geometry and reflective characteristics of the sill complex.

Clear evidence of the Winagami reflection sequence emerges from the dataset acquired
to 5.1 seconds two-way-traveltime (approx. 15 km depth) over an area of 400 km^2. Data sections outline a 3-D reflective sheet dipping to the southeast. From a combination of 1-D and 3-D forward modelling, the sheet's depth and thickness are estimated. Comparisons of waveform polarities from the sedimentary sequence with those from the sill complex provide impedance constraints for the deep reflectors. Based on inferences from the seismic results, the sill complex is interpreted to have been intruded horizontally into the crust from multiple injections of magma during tectonic compression. The emplacement of these sills may have ultimately strengthened the crust and helped stabilize this portion of the North American craton. Furthermore, the sills may have provided the strength and rheological contrasts to generate uplift in the presence of weak intraplate stresses, uplift that may have resulted in the development of the Peace River cratonic arch. This arch influenced later depositional patterns
and thus dictated the present-day distribution of oil and gas resources in northwestern Alberta.

Biography
J. Kim Welford is a Postdoctoral Fellow within the Teleseismic and Active Source Seismology Group in the Department of Earth and Ocean Sciences at the University of British Columbia. She holds a B.Sc. in Planetary Sciences from McGill University, an M.Sc. in Geophysics from UBC and received her Ph.D. in Geophysics from UBC in the fall of 2004. Generally, her research interests focus on the application of controlled-source seismic methods to solve Earth science problems. More specifically, she uses crustal-scale seismic techniques to image crustal and upper mantle structure and integrates these results with both geological information and results from other geophysical methods in order to better understand the "big picture" tectonics that have shaped our planet. Her doctoral work focused on the use of industry-acquired 3-D seismic reflection data for the investigation of Precambrian sills beneath the Western Canada Sedimentary Basin of Alberta. Her M.Sc. work with Lithoprobe (a Canada-wide Earth science research project) involved the use of 2-D refraction/wide-angle reflection seismic data to determine the lithospheric velocity structure across northeastern British Columbia.

Colin G. Farquharson
Assistant Professor
Department of Earth and Ocean Sciences
University of British Columbia
Thursday, January 13, 2005

Abstract
Geophysical electromagnetic methods are primarily sensitive to the electrical conductivity of the subsurface. In turn, the conductivities of subsurface materials can depend on many factors,
including rock type, the presence or absence of ground-water and its salinity, and the displacement of ground water by more electrically resistive hydrocarbons. To get the most from the data obtained with a geophysical electromagnetic survey, one would ideally construct a three-dimensional model of the variation of conductivity within the subsurface via inversion of the data. Unfortunately, this is currently impractical because of the substantial computation time it requires, especially for the large amounts of data that are routinely collected in airborne surveys. A compromise that works well for airborne data is to invert the observed data at each measurement location for a one-dimensional model of the variation of conductivity with depth below that location. The one-dimensional models can then be displayed next to each other to give a multi-dimensional image of the subsurface. This procedure is considerably quicker than a three-dimensional inversion of the data-set as a whole, but yet allows all available aspects of modern inversion methodology to be brought into play (for example, using something other than a sum-of-squares measure for the misfit, perhaps the Huber M-measure, which affords a robust fit to data that contain non-Gaussian noise, and using an l ₁-norm or similar measure of model structure that enables piecewise constant, blocky models to be constructed). Two examples of this strategy will be given, both illustrating the use of airborne electromagnetic methods in the exploration for unconventional hydrocarbon reserves in Alberta, Canada: a frequency-domain survey for shallow gas, and a time-domain survey for oil sands.

Biography
Colin G. Farquharson currently holds a term-limited Assistant Professor position in the Department of Earth and Ocean Sciences at the University of British Columbia, Vancouver, Canada. He obtained a B.Sc. in Geophysics in 1990 from the University of Edinburgh, and a Ph.D. in 1995 from the University of British Columbia. His supervisor was Prof. Douglas W. Oldenburg, and his thesis project involved the development of approximations useful to the geophysical electromagnetic inverse problem. Since receiving his Ph.D., Colin has held post-doctoral and Research Associate positions with Prof. Oldenburg in the Geophysical Inversion Facility at U.B.C., before becoming an Assistant Professor in July 2002. His research interests are in the development of theory and algorithms for the forward modelling and inversion of geophysical electromagnetic data. His current work includes: the testing and application to field data of a three-dimensional magnetotelluric inversion program; finalizing a one-dimensional inversion program for time-domain electromagnetic data that, amongst other things, can handle most typical survey geometries and incorporates general measures of misfit and model structure; and comparing forward modelling results from a new three-dimensional integral equation formulation with those from physical scale modelling. He has written three inversion programs, and contributed to a fourth, that have been distributed to the industrial sponsors of the Geophysical Inversion Facility and the wider geophysical community. Colin has taught a number of applied and theoretical undergraduate geophysics courses, and has been and continues to be involved in the supervision of undergraduate and graduate student theses.

Chris Okubo
Ph.D. Candidate
Department of Geological Sciences and Engineering
University of Nevada, Reno
Thursday, January 20, 2005

Abstract
A detailed mechanical understanding of the tendency for the nucleation and propagation of fault slip-induced plastic yielding is a key to evaluating the origins of fault-related damage zones and their effect on fault growth, stress transfer, and energy budget, as well as to evaluating the effect of strain localization on the morphology, fracture structure, and fluid conductivity of fault-related folds on Earth and other planetary surfaces. In this talk, I will present results from a series of studies in which the tendency and mode of plastic yielding (dilatancy vs. compaction) in porous granular rocks are quantified using strain energy density-based criteria and laboratory-defined yield curves. Specifically, critical volumetric and distortional strain energy densities are used to separately describe the tendencies for the nucleation and propagation of localized brittle strain in the form of deformation bands. This method successfully predicts the geometries and intensities of fault-related damage zones within reservoir-scale folds and thereby provides insight into attendant changes in the porosity and permeability of the host rock, which has a potential for compartmentalizing reservoir fluids and influencing subsequent fault growth.

Results of laboratory testing and numerical modeling of strain energy density predict distributions and intensities of deformation bands that are consistent with field observations of damage zones within the Laramide-aged Uncompahgre fold in western Colorado, as well as in other field sites in Utah and Nevada. Deformation band nucleation is a precursor to the formation of through-going faults within porous granular rock (e.g. sandstone or tuff). Because of the strain-hardening nature of deformation bands, erosional exposures of deformation band
damage zones form high-relief ridges that are on the order of meters, to in excess of hundreds of meters, in length. Accordingly, these damage zones are readily apparent in aerial photographs of Earth.

Morphologically similar high-relief ridges are present on Mars within erosional exposures of the 'Interior Layered Deposits' in the Valles Marineris region. These candidate fault-related deformation band damage zones are found along-strike of 'wrinkle ridges' that are apparent along the tops of the surrounding plains. Inverse numerical modeling of satellite-based wrinkle ridge topography reveals these morphologic features to be the surface expressions of thrust fault-related folds. This finding supports the interpretations of down-strike (and down-dip) deformation band damage zones within the Interior Layered Deposits.

Interpretations of deformation band damage zones within the Interior Layered Deposits provides insight into the mechanical character of these enigmatic deposits. The growth of deformation band damage zones here implies that these deposits are porous and granular in nature, supporting photogeologic interpretations of volcanic airfall origins. Further, evidence for near-surface volatiles on Mars is abundant, and the existence of deformation band damage zones within the Interior Layered Deposits suggests a potential for significant compartmentalization and directed flow within local volatile reservoirs.

Biography
Chris Okubo is a graduate student with the Department of Geological Sciences and Engineering, Mackay School of Earth Sciences and Engineering, at the University of Nevada, Reno. He holds a B.S. (1997) in Geology & Geophysics from the University of Hawai`i, and is on track to receive a Ph.D. in Geological Engineering from the University of Nevada, Reno in May 2005. He is a recipient of two 'Honorable Mentions' from the Geological Society of America for presentations at the Lunar and Planetary Science Conference (2002, 2004). He has seven published papers, and four in review, and has previously presented invited talks at the Lunar and Planetary Institute and at Shell International Exploration and Production. His main research interests are in rock mechanics, fault mechanics, volcano stability, remote sensing, and planetary tectonics. Further information is available at http://equinox.unr.edu/homepage/chriso.

Abstract
Seismic depth imaging consists of two steps: velocity estimation and migration. The interdependence of the two steps increases with increasing complexity of the velocity function (e.g. subsalt). In complex depth imaging problems, velocity estimation and migration are
applied in an iterative loop: a velocity model is needed for migration, and a migrated image is needed for velocity analysis. A first requirement for convergence of the iterative seismic imaging loop is that migration and velocity analysis are consistent with each other.

Imaging under salt is difficult mainly due to strong velocity contrasts between salt bodies and
their surrounding sediments. Those large velocity contrasts, often combinedwith complex salt geometries, generate distorted wave propagation patterns. Subsalt wavefields are characterized by multiple-paths in some regions and by poor illumination in others. Furthermore, multipathing and uneven illumination are frequency-dependent phenomena, so processing outside the band of the recorded data increases the difficulty and inaccuracy of seismic imaging. Therefore, a second requirement for accurate seismic imaging is that velocity analysis be done in the band of the recorded data.

Given the complexity of subsalt velocity analysis, we need to use as much information from the recorded data as possible in order to achieve the highest accuracy. We need to use all thecomplexities contained in the seismic images for MVA, and not only the information
derived from picked reflectors. Thus, a third requirement for accurate seismic imaging is that all recorded data be used for MVA and not only sparse information picked at a few selected reflectors.

The current state-of-the-art methods of seismic imaging violate all three requirements
stated above. Migration if often performed using band-limited algorithms (e.g. migration by wavefield extrapolation), but migration velocity analysis involves traveltimes computed by ray tracing, corresponding to an infinitely-wide frequency band. Therefore, migration and velocity
analysis are inconsistent with one-another, migration velocity analysis is inconsistent with the frequency band of the recorded data, and the information used for velocity analysis is limited to a few main reflectors picked on migrated images.

Wave-equation migration velocity analysis, advocated in this presentation, aims at addressing
all these deficiencies of subsalt velocity analysis. This method is closely related to migration by wavefield extrapolation, it is formulated in the frequency band of the recorded data, and it
employs the information from the entire images to constrain the velocity model. I present the theory of the method and illustrate it with seismic and Ground Penetrating Radar applications.

Biography
Paul Sava is a Research Associate with the Bureau of Economic Geology at the University of Texas (Austin). He holds an Engineering degree in Geophysics (1995) from the University of Bucharest, an M.Sc. (1998) and a Ph.D.(2004) in Geophysics from Stanford University where he was affiliated with the Stanford Exploration Project. He is a recipient of a Stanford Graduate Fellowship (1997-2000) and of two awards of merit for best student presentations at the SEG conventions (1999, 2001). He has received a Honorable Mention in the category Best Paper in Geophysics for "Angle-domain common-image gathers by wavefield continuation methods" published in 2003 and co-authored by Sergey Fomel. His main research interests are in seismic imaging and velocity analysis using wavefield extrapolation techniques, computational methods for wavepropagation, optimization and high performance computing. He is a member of SEG, EAGE, AGU, SIAM, and RSG.

Abstract
The spatially dense observations of deformation provided by InSAR can help us constrain the kinematics of interseismic, coseismic and postseismic crustal behavior, especially when combined with seismic data and other types of geodetic observations. Our goals may range from simply providing precise hypocentral locations to characterizing the coseismic fault slip distribution and/or interactions with aftershock locations, postseismic deformation and variations in fault zone properties. As the spatial and temporal data coverage spanning these events continue to expand, it is becoming increasingly important to have consistent, semi-automatic methods for performing our inversions. We also must quantify the uncertainty in our parameter estimates in ways that are useful to the broad spectrum of users who adapt our results to their particular applications.

In this talk, I will present our work on the following two topics:

1: What can InSAR tell us about the spatial distribution and style of seismicity that characterizes zones of continental deformation in remote regions that lack dense local seismic networks? We examine the Zagros mountains of southern Iran and present examples of the precise hypocentral locations that can be inferred for events as small as Mw 4.2. We show how neglecting the spatial covariance of atmospheric noise can result in unrealistically small confidence limits on the location.

2: What are the characteristics of coseismic slip distributions for large earthquakes and how much do they vary within or between fault types such as large, continental strike-slip systems or subduction zone environments? To answer these questions, we require consistent, semi-automatic inversion techniques that can be applied to earthquakes with a wide range of signal-to-noise ratios and different amounts of pre-existing information about the fault plane geometry and crustal rheology. We apply our inversion technique to data spanning the 1995 Antofagasta, Chile, and 1998 Hector Mine, California, earthquakes and examine the dependence of the inferred slip distribution on our knowledge of the fault plane location. We also show differences between inversions using spatial roughness and spatial compactness as constraints, and compare how these different models would drive postseismic deformation.

Biography
Rowena B. Lohman is currently a postdoctoral scholar at Woods Hole Oceanographic Institution. Her research interests all involve understanding how the crust accommodates strain over timescales that span a single earthquake up to several seismic cycles. She received both her Ph.D. in geophysics and B.S. in geology from the California Institute of Technology. Her thesis involved the inversion of InSAR and GPS observations for earthquake locations in remote regions, and for properties of the coseismic slip distributions for larger (Mw >7) earthquakes. In the course of this work, she developed techniques for accounting for spatially correlated atmospheric noise, inadequate knowledge of crustal rheology, and methods for efficiently dealing with the large size of InSAR datasets. Her postdoctoral research will focus on interpreting postseismic deformation, including the use of models of fault zone dynamics and understanding the dependence on inversion methods used to generate the coseismic slip distribution. She is also examining how the neglect of realistic 3-D variations in elastic parameters may bias fault slip inversions.

Abstract
Migration, Tomography and Datuming by Seismic Interferometry

Biography
Gerard T. Schuster

Abstract
The Mw 7.9 Denali Fault earthquake on 3 November 2002 demonstrated that rupture of secondary thrust faults can trigger nearby strike-slip faults, highlighting the possibility that such dangerous earthquakes could occur in more densely populated regions with similar tectonics.
For example, previous workers [Eberhart-Phillips et al., 2003] have suggested that an earthquake similar to the Denali fault mainshock could occur in the Los Angeles metropolitan region, home to more than 13 million people. In this talk I will discuss how we have tested this proposal by modeling dynamic stress interactions between the Sierra Madre-Cucamonga thrust and San Andreas/San Jacinto strike-slip fault systems near Los Angeles. I will show that the comparison with the Denali fault mainshock breaks down due to differences in background
stress field and fault geometry. In particular, rupture of the Sierra Madre-Cucamonga system is unlikely to trigger rupture of either the San Andreas or San Jacinto fault, as the Susitna Glacier fault triggered the Denali fault during the 2002 event. However, our modeling suggests that under rare circumstances, a large earthquake on the northern San Jacinto fault could trigger a cascading rupture of the Sierra Madre-Cucamonga system, potentially growing into a dangerous Mw 7.5-7.8 earthquake on the edge of the heavily populated Los Angeles metropolitan region.

Biography
Brad Aagaard is a research geophysicist in the U.S. Geological Survey Earthquake Hazards Team in Menlo Park, California. His research focuses on understanding the physics of earthquakes to better predict damaging ground motions. He received his B.S. in engineering from Harvey Mudd College and M.S. and Ph.D. degrees in Civil Engineering from the California Institute of Technology. His thesis research focused on parameter studies of near-source ground motion using both kinematic and spontaneous rupture earthquake source models. He developed the 3-D finite-element code used in his studies. While a postdoctoral scholar in geophysics at the California Institute of Technology Seismological Laboratory and a Mendenhall Postdoctral Scholar at the Pasadena USGS office, Brad Aagaard has continued enhancing his finite-element software and has used it to study the shaking in the 1999 Chi-Chi earthquake, the complex rupture propagation in the 2002 Denali fault earthquake, and the potential for complex rupture in the Los Angeles area.

Abstract
Local event slopes capture the geometrical nature of seismic reflection data. They provide both a theoretical tool for understanding the geometry of seismic imaging and a practical tool for efficient seismic data processing.

Estimating local slopes from the input data amounts to a specially constructed inverse problem. The problem is solved efficiently by regularized iterative opitimization. Estimated slopes are useful for accomplishing common data processing tasks such as data regularization and noise attenuation.

One can also incorporate seismic slopes directly into time-domain imaging procedures such as normal and dip moveout, prestack time migration, and anisotropic Dix inversion. The new formulation does not only bring an order-of-magnitude improvement in efficiency but also changes the role of seismic velocities: instead of being a crucial processing parameter, velocity turns into a secondary attribute.

Finally, local slopes extend the time and space domain for describing the wave propagation phenomenon. The so-called oriented wave equation describes wave propagation in the local slopes domain and opens new horizons for high-resolution seismic depth imaging of the future.

Biography
Sergey Fomel is a Research Scientist at the Bureau of Economic Geology, University of Texas at Austin. He holds a Ph.D. in Geophysics from Stanford University. Sergey worked for the Institute of Geophysics in Novosibirsk (1990-1994), Schlumberger Geco-Prakla (1998), and the Lawrence Berkeley National Laboratory, where he also taught at the University of California (2001-2002). His research interests are in computational and exploration geophysics, seismic imaging, and geophysical inversion. In 2001, Sergey was honored with a J. Clarence Karcher award from the Society of Exploration Geophysicists "for numerous contributions to seismology".

Abstract
Airborne laser altimetry, also known as airborne laser swath mapping (ALSM) and light detection and ranging (LiDAR), is quickly becoming popular for generating high resolution digital elevation models (DEMs) for geomorphic and hazards mapping. While LiDAR data can easily be used to develop DEMs and provide first level ‘visual’ mapping; it can also be used to assess the surface roughness of geomorphic surfaces (e.g. landslides, moraines) and tectonic landforms (e.g. fault scarps) with statistical measures. This study uses small footprint LiDAR to define the surface morphology of two canyon-rim landslides (Salmon Falls and 1937 landslides) in southern Idaho and relate the morphology to field measured motion. Surface roughness is calculated based on local topographic slope derived from the LiDAR high resolution elevation data (5 cm relative accuracy). Semivariograms and fractal dimensions are also used to assess surface characteristics with the elevation data. Weak, unconsolidated materials comprising the toe of the Salmon Falls slide, which were heavily fractured and locally thrust upward, had relatively high surface roughness, high spatial correlation, high fractal dimension, and high vertical and lateral movement. The body of the slide, which predominantly moved laterally and consists mainly of undisturbed, older canyon floor materials, had relatively lower surface roughness, spatial correlation, and fractal dimension than the toe. The upper block, consisting of a subsided section of the canyon rim that has remained largely intact, had low surface roughness and spatial correlation, and a fractal dimension representative of smooth topography. The topographic analyses also demonstrate that the Salmon Falls landslide has a similar failure mechanism and is topographically rougher than the 1937 landslide. Results from the 1937 slide demonstrate that high resolution topographic data have the potential to differentiate failure zones within a landslide and provide insight into the material type and activity of the slide. With the potential for full waveform returns from LiDAR systems and the ability to couple this data with GPS, geophysical, and other high resolution spatial/temporal data, the opportunities for hazard analyses will only become more sophisticated.

Biography
Nancy Glenn is an assistant research professor in the Department of Geosciences at Idaho State University (ISU) Boise Center. Her area of interest involves remote sensing and geological engineering. She has both teaching and research responsibilities at ISU, as well as research obligations at the Idaho National Engineering and Environmental Laboratory (INEEL). Dr. Glenn established ISU’s remote sensing program in 2000 and has expanded this program to the Boise, Idaho area by establishing the ISU Boise Center Aerospace Laboratory (BCAL). Dr. Glenn’s experience in remote sensing processing and interpretation ranges from synthetic aperture radar (SAR), hyperspectral, light detection and ranging (LiDAR), to the visible and near-infrared. Her work also incorporates high resolution global positioning systems (GPS) and the use of geographic information systems (GIS) for field validation of high resolution hyperspectral and LiDAR data.

Abstract
Limited signal bandwidth and abundant thin layering interact to produce tuned seismic reflections with peaks, troughs and zero-crossings that rarely follow true geologic boundaries. Such interference plagues traditional seismic methods and hinders the extraction and characterization of subsurface information.

While conventional interpretation techniques require constant attention to the source wavelet and its associated tuning-thickness and dominant frequency, spectral decomposition facilitates the process. It moves detection and resolution out from under the control of the source wavelet and allows impedance and thickness interference to be examined with respect to signal and noise on a frequency-by-frequency basis. Just as remote sensing makes use of sub bands of much higher electro-magnetic frequencies to characterize the earth's surface, spectral decomposition relies on sub-bands of substantially lower seismic frequencies to characterize the earth's subsurface.

This simple and robust seismic technology has been implemented by many seismic contractors and has led to higher resolution and improved interpretation on many plays throughout the world. It reveals and facilitates assessment of stratigraphy, structure, thickness, heterogeneity and reservoir architecture. By providing higher fidelity and superior fault imaging than conventional amplitude/attributes, it often reduces uncertainty, and facilitates integration of seismic, geology and reservoir simulation.

In this talk, my goal is to leave you with a better understanding of this technology via real and model case studies. Along the way, I hope to provide insight into the creative process that led to its development. I will include a discussion of the frequency domain characteristics of a layer, analysis window size and spectral balancing, and will wrap-up with some thoughts regarding the road-ahead.

Biography
Greg Partyka received a degree in Geological Engineering from the University of Manitoba in 1987. Since 1988, he has worked for Amoco, then BP, in Canada, Poland, United States and United Kingdom.

He has moved back and forth between assignments in operations and technology. This mix of roles has allowed him to experience research, development, application, and just as importantly, the value that appropriate technology can bring to business decisions. Along the way, he has focused his efforts on multi-disciplinary problem solving and improving our ability to decipher geologic content embedded in seismic data.

In 1996 he deepened his knowledge of reservoir characterization by participating in an intensive, yearlong petrophysics training program.

In 2003 he received the SEG Virgil Kauffman Gold Medal for his work on the development of the spectral decomposition technique for reservoir characterization. This technique has been implemented by many seismic contractors and has led to improved interpretation on many plays throughout the world.

His current role at BP, allows him to collaborate with teams and individuals throughout the upstream organization, impacting BP's exploration and production activities worldwide.

Abstract
In order to better characterize seismic hazard and the properties of fault friction, we use InSAR, GPS, teleseismic, and strong motion data to constrain the location of seismic and post-seismic slip for 15 earthquakes in southern Peru and northern Chile. We invert body-wave waveforms and geodetic data both jointly and separately and find that while the location of slip in the sieismic-only, geodetic-only, and joint slip inversions is similar for the small earthquakes (Mw < 8), there are differences for the larger events, probably related to non-uniqueness of models that fit the seismic data.

By combining the GPS and InSAR data we estimate the spatio-temporal evolution of post-seismic after-slip following the four Mw > 7 earthquakes within our study area. In northern Chile, we find little after-slip (10-20% of co-seismic slip) compared to other recent subduction zone earthquakes and a 2001 earthquake in southern Peru. Furthermore, while after-slip is down-dip of the co-seismic rupture in Chile, after-slip in Peru is within the seismogenic zone. There is an aseismic pulse of deformation in northern Chile that appears distinct from the general decay of after-slip with time and may have triggered a large aftershock in 1998. We propose that the differences in after-slip in northern Chile and southern Peru are related to the amount of sediment subducted.

Biography
Matt Pritchard is an assistant professor in the Department of Earth and Atmospheric Sciences at Cornell University. His current research is focused on three main areas: 1) the subduction zone earthquake cycle; 2) magma transport; and 3) planetary geophysics. Future work includes comparing deformation rates over short time periods (as measured by InSAR and GPS) to longer term deformation rates.

During 2004 he was a Harry Hess postdoctoral fellow at Princeton University. In 2003, he received a Ph.D. in geophysics with a minor in planetary science from the California Institute of Technology. His B.A. degree is in physics from the University of Chicago.

Abstract
The method of Probabilistic Seismic Hazard Assessment (PSHA), which has been used by the United States Geological Survey (USGS) since 1976, is used to construct a set of seismic hazard maps for Iraq. Seismic hazard estimates are determined by first gathering a catalog of recorded earthquakes that occurred in Iraq. I use the International Seismological Center (ISC) Bulletin, Preliminary Determination of Epicenter (PDE), and Engdahl and Villasenor (EV) catalogs. These catalogs are combined to create a catalog of 1,359 events in and around Iraq that range in magnitude from 3.5 to 7.8. I then determine the minimum magnitude of completeness of the catalog. The minimum magnitude of completeness indicates the minimum magnitude at which the catalog contains all earthquakes that have occurred. The minimum magnitude of completeness since 1962 is 4.7. The probability of exceeding specific peak ground accelerations (PGA) and spectral accelerations (SA) over the next 50 years is estimated as a function of location. These are then contoured and plotted.

Biography
Jessica Schwark received her Bachelor’s degree in Geophysics from Texas A&M University in May 2003. Upon her arrival at Mines in the fall of 2004, she joined a group at the USGS to work on constructing seismic hazard maps for Iraq. Over the summer of 2004, she interned with Union Oil Company (Unocal) in Sugar Land, Texas where she worked as an office geophysicist mapping the suprasalt sections in the deep water Gulf of Mexico. While at Mines, she has been a teaching assistant for SYGN 101 students and has participated on the department’s intramural volleyball team. Jessica has been an SEG member and scholarship recipient since 1999.

Reservoir Characterization for Tight Gas Sands:
The Rock Physics and Seismic Aspects

Abstract
The rock physics of tight gas sandstones (low permeability and low porosity) has been relatively neglected. Today tight gas is a vast resource, especially in the Rockies, and new production technologies are being developed to exploit this natural resource.The Williams Fork formation in Rulsion Field is thick, containing up to 135 Bcf per section, but sands are lenticular and discontinuous, so the drainage area is limited. Technology improvements are needed to successfully produce low permeability gas reservoirs. My study links rock physics to well log and seismic data for prediction of better areas to develop, based on integrated reservoir characterization. I will show rock physics trends for tight gas sandstones, obtained from laboratory measurements in cores and cross dipole sonic log analyses. These trends can be used as a tool to identify “sweet spots” in Rulison for further development. Relations between P-, S-wave velocity and permeability are studied grouping and sorting rocks into hydraulic units. V p/V s ratio sensitivity to effective pressure changes, lithology, fluid content, porosity and permeability is studied to link elastic responses of tight gas sands to rock and fluid properties.

Biography
Eugenia Rojas obtained her BS degree in Geophysical Engineering from Simon Bolivar University (Caracas, Venezuela) in 2001. She worked for Schlumberger and Intevep-PDVSA (Venezuelan Research Institute). In 2003 she started work towards her MSc in Geophysics at the Colorado School of Mines with the Reservoir Characterization Project. In addition she has been doing experimental work in the Center for Rock Abuse. After finishing her degree, Eugenia plans to work for Anadarko in Houston.

Azimuthal NMO Analysis of Weyburn 3D Shear-waves

Abstract
Azimuthal analysis of p-wave data is gaining popularity for better stacking of p-wave data, stress orientation, fracture detection, etc (see Jenner 2002). I have been developing azimuthal analysis techniques using pure shear wave data. Goals of my work include: high resolution azimuthal velocity analysis, more accurate stress orientation, more accurate differentiation of azimuthal velocity anisotropy and magnitudes of velocity change, more accurate stress orientation, better fracture detection and quantification, and better processing of shear wave data.

The application of azimuthal analysis to shear-waves must overcome the low signal-to-noise characteristic of shear-wave records. To this end I have developed a horizon-based approach using weighted least-squares for the azimuthal analysis and applied it to pure shear modes from the Weyburn 3D surveys. To quantify the effects of noise on the analysis, I simulated shear-wave 3D data with residual normal moveout corresponding to a single-layer azimuthal velocity model and having the same geometry as for the Weyburn acquisition. I then applied the azimuthal analysis to the simulated data with several levels of additive noise. This noise study provides a means of judging the accuracy of results of azimuthal analysis of the actual shear-wave data.

There are several issues addressed in this study including how much noise can be tolerated, what processing can be applied to increase signal-to-noise without masking or distorting the azimuthal effects, what kind of velocities can be achieved and what degree of smoothing or averaging can be effective in producing useful results.

Abstract
Because the risk of earthquakes in Los Angeles is greater than for any other city in the United States, determining which faults are moving and how they move is an essential step in assessing earthquake hazards. After the Whittier Narrows and Northridge earthquakes revealed that blind thrust faults threaten metropolitan Los Angeles, an array of 250 continuously-recording GPS stations (Southern California Integrated GPS Network - SCIGN http://www.scign.org) was deployed to detect and monitor the motion associated with the movement of the blind thrusts (inclined faults that do not reach the surface) and the surface faults. Here we augment the GPS measurements with interferometric synthetic aperture radar (InSAR) imagery and find that the Palos Verdes peninsula is moving towards the San Gabriel mountains at a rate of 4.4 mm/yr + 0.8 (%95 confidence) (0.2 in/yr). This motion can only be explained by slip on the thrust faults that lie beneath the greater metropolitan Los Angeles region.

We also find that widespread ground water and oil pumping across Los Angeles produces measurable surface motion that is, in some locations, larger than the expected signal from slip on the blind thrust faults. SCIGN was able to detect and measure these human-induced surface motions that may have gone unnoticed for a number of years, potentially biasing geodetic seismic hazard assessments for Los Angeles. While SCIGN was developed to study how the Earth's surface deforms between and during large earthquakes, it has become a valuable resource for characterizing aquifer storage. For an interactive map, see: http://quake.wr.usgs.gov/research/deformation/modeling/socal/la.html

Biography
Gerald Bawden is a research geophysicist for the US Geological Survey, Water Resources Division, Sacramento, California. He recently established the USGS Western Remote Sensing and Visualization Center as a cross-discipline facility designed to foster new collaborative research projects among the USGS disciplines. His research group is currently: 1) using interferometric synthetic aperture radar (InSAR) and Global Positioning System (GPS) measurements to characterize and model the three-dimensional deformation field associated with Aquifer Storage and Recovery programs and overdrafted aquifers; 2) mapping the spatial extent of ground-water barriers with InSAR; 3) evaluating if InSAR can be used to identify subsidence precursors to mine shaft/tunnel collapse; 4) recognizing and removing anthropogenic deformation associated with ground-water and hydrocarbon pumping in tectonic GPS networks; 5) imaging debris flows with tripod-mounted Lidar to help mitigate the hazards following the 2003 southern California wildfires and the 2004 Carson City Fire, Nevada; 6) developing new techniques for collecting indirect flood measurements and habitat change with tripod-mounted Lidar; and 7) using tripod-mounted Lidar to map surface changes following the 2004 Parkfield earthquake.

Dr. Bawden has taught Active Tectonics in the University of California Davis summer field program and currently is co-directing two master's degree candidates. He earned a Bachelor's degree from the University of California, Santa Barbara, and Master's and Ph.D. degrees from the University of California, Davis, all in geology.

Abstract
Since their discovery, aseismic slip phenomena such as steady fault creep and slow earthquakes have changed seismic hazard assessment. Aseismic slip is an important caveat to the seismic gap hypothesis; it accommodates plate motion without large earthquakes and will lower a fault’s assessed hazard. Transient phenomena, such as triggered creep, indicate that creeping faults are very sensitive to stress changes. Creeping faults may therefore transmit input stress along the fault plane, ultimately bringing the adjacent locked portions closer to failure. Besides modifying the slip budget, the distribution of creep on a fault can indicate where large earthquakes will occur. In areas with a heterogeneous distribution of fault creep, the creeping area has been observed to be anti-correlated with the earthquake rupture area. This occurs because the frictional properties that are thought to allow creep also prevent the nucleation and inhibit the rupture propagation of large earthquakes.

For the Geophysics Day talk, I will present some of the history of creep measurements on the San Andreas fault and how advances in detection and modeling have led to the results described above. I will focus on the San Juan Bautista segment of the San Andreas fault; using it as an example of the methods used to measure creep at the surface and sub-surface, and as a illustration of how creep distribution informs seismic hazard assessment. The San Juan Bautista segment is a transitional segment between the creeping section in the south and the locked portion that last slipped in the 1906 earthquake. Here the San Andreas fault experiences steady surface creep and transient slip events. Consistent with an actively creeping fault, the largest instrumentally recorded earthquakes on the San Juan Bautista segment have been moderate; between M5.3-5.5. However, historic records suggest six M~6 earthquakes ruptured the San Juan Bautista segment between 1840 and 1899. Creepmeters, strainmeters and alinement arrays have measured surface creep since the 1960s. We now apply space geodetic methods to determine the current distribution of aseismic slip in the sub-surface. A joint inversion of GPS and InSAR data shows two low slip/locked patches with sufficient moment deficit accumulation rate to make them possible source regions for M~6 earthquakes in this area.

Biography
Ingrid is a Ph.D. candidate with the Active Tectonics group at the University of California, Berkeley. She received her B.S. in physics from UCLA in 1998. Her research has focused on the interactions between aseismic creep, creep transients and earthquakes. She uses InSAR and GPS to study the transition of the San Andreas Fault from creeping to locked behavior and the effects of the San Simeon and Parkfield earthquakes on San Andreas creep rates. She has developed techniques for using InSAR to detect the small signals produced by creep and interseismic strain accumulation. While at UC Berkeley, Ingrid was closely involved with the creation of BAVU, a comprehensive GPS dataset for the greater San Francisco Bay Area

Abstract
An image-driven visualization approach that allows images of scientific data from any software package to be treated as a source for generating a surface and overlay will be discussed. The largest barrier in using images as a means to construct three-dimensional surfaces or compare different attributes is a non-linear color map. In most cases it is difficult, if not impossible, to express the linear nature of the data by extracting the color values. It becomes necessary to find a technique that will quickly convert the color values back to linear, scalar quantities that can then be treated as being proportional to the original data.

Once an image with meaningful scalar values exists, that image can serve as a source for generating a three-dimensional surface. The surface retains the characteristics of the original data; however, it becomes a new object with the ability to carry a texture or to attach different information to the surface structure. Clearer communication of complex information in survey designs and automated three-dimensional visualization scripts are easy to accomplish. Since the approach is real-time, a series of first-look techniques are created which includes being able to sort regions of higher anisotropy in a seismic volume. In addition, the approach presents a way to validate different sources of information, such as two different interpreter’s analysis of the same data, and localize areas of interest or change between them.

Biography
Michael Ewing obtained his BS degree in Geophysical Engineering from the Colorado School of Mines in 2002. Returning to CSM for a Masters degree, he focused on visualization efforts and applications. During the summer of 2003, he interned with a research group from ChevronTexaco to develop quantitative image-based visualization techniques. Michael has spent the past two years as a teaching fellow in an 8 th grade science classroom through a National Science Foundation (NSF) project.

Abstract
The Reservoir Characterization Project obtained a nine-component, 3D seismic data set at Rulison Field, Western Colorado during the Fall of 2003. This survey is the first in a series of multicomponent seismic surveys acquired to monitor stress changes associated with reservoir depletion and to better understand the subtle fracture networks that determine gas migration and accumulation. This thesis presents the characterization of the complex wrench fault network at Rulison Field, and its linkage to enhanced natural fracture zones and their control on gas development.

Rulison Field produces out of the Cretaceous Mesaverde tight gas sandstones which have extremely low permeabilities. Economically sustainable gas production from the tight gas sandstones at Rulison is greatly enhanced by the presence of natural fractures. Therefore, locating the fracture networks is of utmost importance because they provide the permeability necessary for economic gas production. I found that the occurrence of natural fractures is linked to the regional and local fault geometry, implying that tectonic fracturing is the link to gas production at Rulison. Fracture zones are associated with fault trends and areas of deformation such as structural corners and fault intersections. The subtle, yet complex, wrench faults are difficult to detect and often overlooked in the reservoir interval. To better characterize the faults and fractures at Rulison, a newly developed tool for fault mapping was applied. The Ant Tracker ä algorithm provides a powerful 3-D automated technology for identifying and enhancing the complex faults which are responsible for the generation of natural fractures.

Biography
Kjetil Jansen obtained his BS degree in Marine Geophysics from Eckerd College in 2002. In 2003 he started work towards his M.Sc. in Geophysics at Colorado School of Mines with the Reservoir Characterization Project. After finishing his degree, Kjetil plans to work for Occidental Oil and Gas Corporation in Tupman, California.

A New Method for the Estimation of Total Magnetization Direction

Abstract
The problem of determining total magnetization direction has long been ambiguous in potential field geophysics. For proper interpretation of magnetic data or magnetic anomaly, it is imperative that the true total magnetization direction is known, or closely estimated. In most cases the induced magnetization in the Earth’s ambient field direction is assumed to be the only or dominant component of the total magnetization, therefore its direction is assumed to be known. This assumption can lead to false confidence in the interpretation of magnetic data, because in many cases remanence is present and is strong enough to affect the true magnetization direction. In actuality, the total magnetization is the vector sum of both the inducing field direction and the remanent direction.

 The method presented here is based upon the optimal correlation between two tools in magnetic data interpretation: the vertical gradient and the total gradient of the reduced to the pole field. Reduction to the pole (RTP) is an interpretation tool that transforms a measured total field anomaly to the vertical component of the field that would be generated by the same source distribution. This transformation can only occur when an accurate estimation of magnetization direction is known. When using the vertical component of the field the vertical gradient and total gradient should have the highest correlation as compared to using any other directional projection of the field. The method presented here calculates the RTP over a range of inclination and declination directional pairs. At each pair the two gradient values are determined and correlated, with maximum correlation occurring at a close approximation to the true total magnetization direction.

Biography
Neal Dannemiller obtained his BA degree in geology from Lawrence University ( Appleton, WI) in 1998. Prior to coming to CSM he did some graduate work in the geosciences department at Western Michigan University (Kalamazoo, MI) and worked in shallow geophysics for the Maryland Geologic Survey (Baltimore, MD) and Blackhawk Geoservices (Golden, CO). In January of 2003 he started work towards his MSc in geophysics at the Colorado School of Mines with the Center for Gravity, Electrical, and Magnetic Studies (CGEM). After finishing his degree, Neal plans to work for Shell in New Orleans.

Dynamic Triggering of Landslides

Abstract
The dynamic stress generated by earthquakes is one of the major causes for triggering landslides. There are many methods which try to characterize the ground motion generated by earthquakes, although, the role of dynamic effects in slope failure is not completely understood. Current methods depend on shear failure to assess landslide potential while the triggering of tensile failure is not clear. In this project I develop a model to investigate the dynamic stress associated with ground motion and show how this can be used to demonstrate the role of both shear and tensile failure in the initiation of slope instability.

This model includes a 1D finite element wave equation code to generate the dynamic stress from an incoming plane wave that is added to static stress of a homogeneous infinite slope. This allows us to test for a variety of wave propagation scenarios to gain insight into the mode of failure.

Providing examples for different failure mechanisms, I show how we find both tensile and shear failure to exist due to an incoming plane wave and their relationship to depth within the slope. This project provides valuable insight into the generation of slope failure and may help to guide landslide mitigation efforts.

Biography
Tamara Gipprich received her B.S. degree in Geology from The University of Michigan in May 2002. She was granted a National Association of Geoscience Teachers internship at the U.S. Geological Survey in Reston, VA as a cartographer where she obtained skills in mapping, GIS and satellite imagery. In 2003, she started work towards an M.S. degree in Geophysics focusing on hazards studies. After completing a satellite imagery study for Space Imaging in 2003, she began research on dynamic triggered landslides. After finishing her degree, Tamara is considering joining the government workforce in Washington, D.C.

Effects of data filtering on inversion of gravity gradient data

Abstract
Gravity gradiometer data are affected by high-frequency noise originating from the movement of the platform. Low-pass filters are often applied to remove such motion-related noise. The filtering, however, does not discriminate between signal and noise and removes both from frequencies outside the pass band. As a result, the anomalies become wider and their amplitudes become smaller. If this effect is not taken into consideration, interpretation of such data produces source bodies that are deeper and wider than the true sources. In my research, I first quantify the errors in the inverted models that result when the low-pass filtering is ignored using a simple parametric example, and then incorporate the low-pass filtering into the forward modeling and sensitivity calculations. This ensures that the forward operator includes both the physics and acquisition system characteristics, and hence, that it is consistent with the data to be inverted. Application to synthetic examples demonstrates that such an approach can largely ameliorate the adverse effect of low-pass filtering. Within this context, I will also examine the commonly accepted definition of data misfit based on the inverse of covariance matrix of data noise. I will demonstrate that the covariance matrix of filtered data set is singular and therefore alternative definition is required.

Biography
Jeongmin Lee obtained his BS degree in Earth Science education and MS degree in Science education from Seoul National University ( Seoul, Korea). He worked for Korea Resources Corporation (KORES). In 2003 he started work towards his MSc in Geophysics at the Colorado School of Mines with the Center for Gravity, Electrical, and Magnetic Studies (CGEM). Jeongmin is planning to return to KORES and work in mineral exploration after completing his MSc

Improving UXO discrimination using magnetic quadrupole moments

Abstract
Land contamination with unexploded ordnance (UXO) is a sleeping giant for the US military. The UXO cleanup problem is a large-scale undertaking involving 10 million acres of land with current estimations of cleanup cost in the tens of billions of dollars. A major factor in reducing the cost of cleanup is to improve upon the UXO discrimination capabilities. Total-field magnetic measurements have proven to be a viable tool for guiding UXO cleanup. The current practice for UXO discrimination recovers the dipole moment of a metallic object and uses the recovered moment to determine the likelihood that a particular target is UXO.

Currently there are no UXO discrimination techniques, based on total-field magnetic data, that rely on moments of higher order than the dipole. In some cases, however, it can be advantageous to characterize a UXO target with both dipole and quadrupole moments. The magnetic quadrupole moment provides valuable information about the shape and orientation of a metallic object.

In this talk I explain these ideas and present synthetic examples that illustrate the behavior of the quadrupole moment for an arbitrarily shaped body. Additionally I present diagnostic parameters of the quadrupole moment that allow for a practical interpretation of the observed UXO response. Preliminary results of the application of this technique to a total-field data set show the value of using the quadrupole moment diagnostic parameters as discrimination criteria.

Biography
David Sinex obtained his BSc degree in geophysics from the Colorado School of Mines in 2000. After graduation he worked for Western Geco for almost two years as a seismic processor. In fall 2002 he started work towards his MSc in geophysics at the Colorado School of Mines with the Center for Gravity, Electrical, and Magnetic Studies (CGEM). After finishing his degree, David plans on continuing research in the field of UXO.