Category Archives: PGS

Potomac Geophysical Society

PGS: Maurer on “The curse of dimensionality in exploring the subsurface”

2015 Near Surface Honorary Lecturer
The curse of dimensionality in exploring the subsurface
Presented by Hansreudi Maurer
ETH Zurich, Switzerland
The term “curse of dimensionality” refers to increases in the dimensionality of model spaces that result in undesirable increases in data sparsity, such that model parameters are no longer sufficiently constrained by the data. Although the term is usually employed in combinatorics, machine learning, and data mining, it is also directly relevant for many problems in exploration geophysics. The most obvious applications are 3D tomographic inversions, which typically include very large numbers of unknowns.
There is a further “curse of dimensionality” and related data sparsity that may impede many geophysical investigations: 3D surveys typically involve the acquisition of data using only a 2D array of sensors distributed across the Earth’s surface. As a consequence, procedures for imaging the subsurface are missing data recorded in the third dimension, depth. Similar problems affect 2D inversions of (1D) profile data.
Computational problems that need to be overcome in large-scale tomographic inversions are additional issues associated with the “curse of dimensionality”. In particular, the rapidly emerging field of realistic 3D full-waveform inversions of elastic and anisotroic data is hitting the limits of current computer facilities. Seemingly ever increasing computing power will undoubtedly be beneficial for such endeavors. Nevertheless, suitable model parameterizations that offer appropriate spatial resolution while keeping the inversion problem computationally tractable will continue to be critical elements of any high dimension inversion endeavor.
Because of the large computational costs and the difficulties to cover extensive areas with geophysical sensors in complicated terrain, many land surveys continue to involve data acquisition along profiles. Such surveys will play a significant role for the foreseeable future. When solving the associated 2D inversion problems, the “curse of dimensionality” strikes again. The underlying 2D assumption that subsurface properties and topography do not change in the third dimension, that is, perpendicular to the tomographic plane, is often unjustified.
The problem of data sparsity can be partially alleviated by employing optimized experimental design and optimized data parameterization approaches. These techniques identify experimental configurations and data representations that optimize data information content and resultant models in a cost-effective manner.
In this lecture, I will illustrate the “curse of dimensionality” by means of several examples from near-surface geophysics. I will present a variety of options for addressing the related problems, including experimental design techniques and optimized model parameterization strategies. I will also discuss problems and remedies related to out-of-plane features in 2D elastic full-waveform inversions.

Hansruedi Maurer is professor for exploration and engineering geophysics at ETH Zürich, Switzerland. His research interests span from algorithmic developments for geophysical tomography to innovative field studies concerned with natural hazards, storage of dangerous waste, exploration of deep geothermal reservoirs, cryosphere research and several other areas, where geophysical techniques provide useful information. A key aspect of his research is the tight coupling of latest developments in numerical modelling and inversion theory with the solution of problems that arise in field applications of magnetic, geoelectric, inductive electromagnetic, ground-penetrating radar and seismic methods. Moreover, he is one of the leading scientists in geophysical experimental design. His contributions in this relatively new research discipline were awarded with the Best Poster Award at the 1997 meeting of the Society of Exploration Geophysics and the 2004 Best Paper Award in Geophysics. He has served as an Editor for Geophysics, and he is an active member of several national and international scientific boards.

An invitation to join the Potomac Geophysical Society

Dear PGS Members and Associates,

It is my pleasure to invite you to join the Potomac Geophysical Society (PGS) for the 2015-2016 season. PGS is a local section of the Society of Exploration Geophysicists (SEG) and an affiliate society of the American Geophysical Union (AGU). Our goal is to encourage interaction among those in the region around Washington, D.C., who have an interest in geophysics or related earth sciences. Over the years, members of PGS have included individuals working in a broad range of government, academic, and private sector jobs.

PGS has continued to remain active and vital largely due to the interest of a dedicated group of loyal members. We would like to encourage you to be a part of this group. If you have not been a member, we ask that you join and attend this year. PGS cannot maintain its vitality without your support. PGS members receive a discounted price of $25.00 for dinner at the monthly meetings; non-members will be required to pay $30.00 for dinner. Members and non-members may attend the presentation only at no charge.

PGS will meet on September 24, 2015, (fourth Thursday); then will meet on the third Thursday of each month at the Officers’ Club at Fort Myer in Arlington, VA. The meetings typically include a social hour starting at 6:00 PM, followed by an optional dinner served at 7:30 PM, and a topical discussion by an invited speaker beginning at 8:30 PM. Our 1st Vice President, Marc Buursink, is busily working on arranging a very interesting series of talks for the upcoming season. If you have recommendations for speakers or discussion topics, any of the officers will be happy to hear from you.

For additional background, information, directions to the meetings, and breaking news about PGS, please check out our website at:

We hope you will be able to join us on a regular basis in 2015-2016. We look forward to seeing you!

On behalf of the PGS Officers,
Catherine Enomoto

President: Catherine Enomoto, U.S. Geological Survey,
1st Vice President: Marc Buursink, U.S. Geological Survey
2nd Vice President: Victor Oancea, SAIC
Secretary: Bob Fraser, U.S. Geological Survey (retired)
Treasurer: Joe Bennett, Leidos (retired)
Website Administrator: Jay Pulli, Raytheon BBN Technologies

AEG/PGS: Conventional Tunneling at Tyson’s Corner

BWH Section of the Association of Environmental &

Engineering Geologists and the Potomac Geophysical Society

Date: Thursday May 21, 2015


Baltimore MD – Washington DC – Harrisburg PA

The Meeting will be held at the Amphora Restaurant, 377 Maple Ave., Vienna VA, 6:00-8:30pm. Reservations are necessary,  we need a head count for the restaurant, so, if you wish to attend dinner ($40, members; $45, non-members), please inform Bob Fraser by May 15th at 703-624-3965 (takes both voice and cell text messages) or via E-mail at Non-members and guests are welcome but must have a reservation. Let’s make this joint meeting a success: make a reservation!

TOPIC: Conventional Tunneling (SEM) at: Tysons Corner, Virginia

PRESENTER: Vojtech Gall, Ph.D., P.E. Gall Zeidler Consultants, Ashburn, VA

BIO: Dr. Gall is a Principal of Gall Zeidler Consultants, a tunnel engineering and consulting company headquartered in Northern Virginia. He has over twenty-five years of experience in the design, construction, and construction management of tunnels and underground structures. He frequently serves on expert review panels dedicated to the investigation and improvement of tunneling schemes ranging from initial inception stages through final design development at bid document level. His services relate to a wide variety of facilities ranging from hydro-power schemes in remote settings to complex transit structures at shallow overburden in difficult, over-built urban settings. He has led tunneling efforts on large infrastructure project such as Dulles Metrorail in DC, the Caldecott 4-th bore tunnel in San Francisco and the East Side Access project in New York City. He holds M.Sc. and B.Sc. degrees in Civil Engineering from the RWTH University in Aachen, Germany, a M.Sc. in Mineral Engineering from the University of Alabama and a Ph.D. in Civil Engineering from the University of Maryland. He is a registered Professional Engineer in 18 states and has authored over 40 technical publications on the subjects of tunneling.

ABSTRACT: The Metropolitan Washington Airports Authority (MWAA) is constructing the Dulles Corridor Metrorail Project (DCMP), which will extend Washington Metropolitan Area Transit Authority’s (WMATA) rail services from the Metrorail Orange Line in Fairfax County, Virginia to Route 772 near Ashburn in eastern Loudoun County, Virginia. The extension will be known as the Silver Line and once completed will add 23 miles to the existing Washington Metro System. The project was subdivided in two phases. Phase I segment is 12 miles long and involves 5 stations (two at grade and three elevated) and was opened to public in 2014. Phase II will extend the rail by another 11 miles with a station at Dulles International Airport and a terminus station in Ashburn.

Both phases use the design-build (DB) delivery method. Phase I was constructed by Dulles Transit Partners (DTP) a Joint Venture of Bechtel and URS and included twin 1,700 feet long single track, 22 feet diameter conventional tunnels (excavated by the Sequential Excavation Method or SEM) that are situated in the urban setting of Tysons Corner.

The presentation will address design and construction of these soft ground tunnels that emerged as the most feasible alternative to practically all other tunneling methods including open and closed face TBM drives and cut-and-cover techniques. Tunneling was accomplished with shallow overburden of as low as about 7 feet from the tunnel crown. Because of the shallow depth, soft ground conditions, and the need to control settlements, the tunnel design included use of a double row grouted pipe arch canopy as pre-support for the first 300 feet of excavation and a single row pipe arch canopy for the remaining length of tunnels thereafter. A real-time monitoring of the surface when tunneling the first 90 m under International Drive was implemented to assure VDOT of the tunneling performance.

PGS: DC Clean Rivers Project

The March 19, 2015 meeting of the Potomac Geophysical Society will be held at the Fort Myer Officers’ Club in Arlington, VA ( in the Glassed-in room in the Fife and Drum (main dining room).

Timothy J. King, P.G. AECOM Germantown, Maryland

The DC Clean Rivers Project is an ongoing program being implemented by DC Water to reduce combined sewer overflows into the Anacostia and Potomac Rivers and Rock Creek. The Project involves construction of a series of storage and conveyance tunnels and related infrastructure to capture and subsequently treat combined sewer water from heavy rainfalls to reduce impacts to the region’s waterways.

Mr. King’s presentation will discuss the application of geophysical investigation methods to the planning and design of tunnels, shafts and related infrastructure associated with the project. Investigations have included seismic surveys to assess subsurface stratigraphy and depth to bedrock, borehole geophysical logging to characterize bedrock discontinuities, multichannel analysis of surface waves (MASW) to delineate buried channels, vertical seismic profiling for seismic design, and side-scan sonar surveys to delineate underwater obstructions.


Timothy King is a Principal Geologist at AECOM (formerly Woodward-Clyde Consultants and URS Corporation) in Germantown, Maryland. He built and is the leader of the geophysical services team at URS/AECOM. His experience includes engineering geophysics, engineering geology, and hydrogeology applied to site investigations to evaluate subsurface conditions related to tunnels, mines, highways, bridges, dams, and other civil infrastructure. He has been responsible for technical and management aspects of investigations at hundreds of sites across the United States and has worked on projects in Africa, South America, Europe and New Zealand.

Hatfield Gate, open 24 hours a day ( Reservations are not necessary, however, we need a head count, so, if you wish to attend dinner ($25), please inform Bob Fraser at 540-888-3001 or via E-mail at If you wish, please feel free to attend the talk without dinner. Non-members and guests are welcome. Visit the PGS web site at for new meeting announcements, etc. Please send changes of address or email to

PGS: Geology and Public Policy – Recent Issues in Virginia

The February 19, 2015 meeting of the Potomac Geophysical Society will be held at the Fort Myer Officers’ Club in Arlington, VA ( in the Glassed-in room in the Fife and Drum (main dining room).

Geology and Public Policy – Recent Issues in Virginia

David B. Spears, State Geologist

Virginia Department of Mines, Minerals and Energy

Government decision makers are faced with difficult choices when it comes to public policy regarding energy and mineral resources. Our nation is heavily dependent on fossil fuels, radioactive isotopes, and rare earth elements that often must be imported from foreign countries to meet U.S. demand. Even though developing our own domestic supplies has obvious strategic advantages, such development often conflicts with other societal priorities such as environmental protection and social justice. To further complicate matters, conflicting pressure is brought to bear on policy makers by an uninformed or misinformed populace that is generally anti-development, and by pro-development businesses who have a financial interest in resource development. In this presentation, Virginia’s State Geologist will use recent, Virginia-specific examples such as uranium mining, offshore drilling, and shale gas to highlight the ways in which government-based geoscientists play a unique role in providing scientific guidance in public debates about how to best manage our nation’s energy and mineral resources.

David Spears is the State Geologist of Virginia, a position residing in the Department of Mines, Minerals, and Energy. He is responsible for coordinating the work of the Division of Geology and Mineral Resources, a small group of geoscientists focused on mapping Virginia’s geology, mineral resources, energy resources, and geologic hazards such as earthquakes, landslides, and sinkholes. In recent years, the State Geologist has played an increasing role in responding to public policy issues such as offshore drilling, natural hazards, and hydraulic fracturing. David received a B.S. in Geology from Lafayette College and a M.S. in Geology from Virginia Tech. He began his professional career in the petroleum industry before coming to Virginia state government in 1993. A native of New Jersey, he currently resides in Buckingham County in central Virginia. In 2012, David received the Bradley Prize from the Geological Society of Washington for his presentation about geology and public policy.

Hatfield Gate, open 24 hours a day ( Reservations are not necessary, however, we need a head count, so, if you wish to attend dinner ($25), please inform Bob Fraser at 540-888-3001 or via E-mail at If you wish, please feel free to attend the talk without dinner. Non-members and guests are welcome. Visit the PGS web site at for new meeting announcements, etc. Please send changes of address or email to

PGS January meeting: Electromagnetic Survey of Potomac River headwaters

The January 15, 2015 meeting of the Potomac Geophysical Society will be held January 15 at the Fort Myer Officers’ Club in Arlington, VA ( in the Glassed-in room in the Fife and Drum (main dining room).

Electromagnetic Survey of the Headwaters of North Branch of Potomac River, Important Tributaries, and Impacting Mines

Paul Petzrick, Maryland Power Plant Research Program, Annapolis, Maryland

In 1999, the National Energy Technology Laboratory (NETL) acquired a Helicopter Electromagnetic Survey (HEM) of the Kempton/Coketon Mine Complex for the Maryland Power Plant Research Program (PPRP). NETL’s interest was in studying remote sensing as a means of identifying water quality problems from mining, and PPRP’s interest was in planning geoengineering projects to permanently restore water quality in streams degraded by abandoned pre-law mines. The 1999 HEM revealed important benefits and limitations of this type of survey that might now be performed by drones. The data from the 1999 survey is particularly important when coupled with other data collected for PPRP by Garrett College and the Western Maryland Regional GIS Center in understanding the massive two-State, 64 square kilometer, surface and underground mine complex that disturbs the headwaters of the Potomac River.

Mr. Petzrick’s presentation will discuss interpretation of the HEM data, the importance of software for conversion of the data to useful graphics for planning restoration projects, and alternate methods of remote sensing and their conversion to useful graphics. The data and its interpretation in each case has been the subject of significant review by NETL and its support contractor and similarly by experts at PPRP’s support contractor, Environmental Resources Management, Inc. The importance of historical information and utilization of water quality data as a tool in assessing environmental issues will also be addressed.


Paul Petzrick is a Senior Engineer and Scientist at the Maryland Power Plant Research Program (PPRP) with a focus on Civil and Environmental Engineering. He has been with this Program in the Maryland Department of Natural Resources for 23 years after finishing 30 years of Federal service that included 20 years as a Navy Civil Engineer Corps officer and 7 years of Senior Executive Service at the U.S. Department of Energy. He had applied mathematics education at the University of Wisconsin and has Engineering Degrees from the U.S. Naval Academy, RPI, and Princeton (M.S. 1966). At PPRP he is primarily responsible for the beneficial use of by-products (ash and CO2) of producing electricity.

Hatfield Gate, open 24 hours a day ( Reservations are not necessary, however, we need a head count, so, if you wish to attend dinner ($25), please inform Bob Fraser at 540-888-3001 or via E-mail at If you wish, please feel free to attend the talk without dinner. Non-members and guests are welcome. Visit the PGS web site at for new meeting announcements, etc. Please send changes of address or email to

PGS: Evolution of the Beaufort Sea

The October 16, 2014 meeting of the Potomac Geophysical Society will be held October 16 at the Fort Myer Officers’ Club in Arlington, VA ( in the Glassed-in room in the Fife and Drum (main dining room).

Seismic Evidence for the Geologic Evolution of the Alaska Beaufort Sea and Adjacent Canada Basin

Dave Houseknecht, U.S. Geological Survey, Reston, Virginia

Integration of 2-D reflection seismic, gravity, and sparse exploration well data from the offshore Alaska Beaufort shelf and slope provides new perspectives on the dynamic tectonic evolution of this Arctic margin. The Beaufort shelf is considered a rift shoulder that developed during Jurassic to Early Cretaceous opening of the Canada Basin, and previous work considered much of the pre-Cretaceous stratigraphy to have been eroded beneath the breakup unconformity. However, reprocessed and newly collected seismic data demonstrate the presence of highly attenuated crust and Jurassic to Lowermost Cretaceous syn-rift strata beneath much of the shelf. Moreover, older strata are present beneath the syn-rift succession, and these include Upper Paleozoic and perhaps Triassic strata, the latter of which may include oil-prone source rocks.

The north-vergent front of the Brooks Range thrust belt is extant beneath the eastern Beaufort shelf, and forms a tectonic wedge and syntectonic wedge-top basin system active since the Paleocene. Upper Paleozoic to Cretaceous strata are deformed by thrust faults and folds within this wedge, and reconstruction of syn-rift extension is difficult as a result. Paleocene through Pliocene strata display a spectrum of growth geometry beneath the shelf and slope, a reflection of syntectonic wedge-top deposition.

This ongoing research contributes to a better understanding of the tectonic evolution of the Alaska Arctic margin, and of the petroleum potential of the region. The results are being used to inform policy makers regarding a disputed maritime boundary between the U.S. and Canada, as well as potential extended continental shelf claims under the U.N. Convention on the Law of the Sea.


Dave Houseknecht is a research geologist with the U.S. Geological Survey (USGS) with a focus on basin analysis, geological controls of petroleum resource distribution, and petroleum resource assessment. This work is mainly concentrated in Arctic Alaska and adjacent Arctic regions. He frequently represents the USGS scientific perspective on petroleum resources in ANWR, NPRA, and other areas of Alaska and the global Arctic to the Administration and Congress. Dave joined the USGS in 1992, serving as Energy Program Manager through 1998 and then moving to a research position. Previously, Houseknecht was a professor of geology at the University of Missouri (1978-1992) and consultant to the oil industry (1981-1992), working on domestic and international projects. He received geology degrees from Penn State University (Ph.D. 1978, B.S. 1973) and Southern Illinois University (M.S. 1975).

Gate, open 24 hours a day ( Reservations are not necessary, however, we need a head count, so, if you wish to attend dinner ($25), please inform Bob Fraser at 540-888-3001 or via E-mail at If you wish, please feel free to attend the talk without dinner. Non-members and guests are welcome. Visit the PGS web site at for new meeting announcements, etc. Please send changes of address or email to