Geology topics

Victor F. Labson

Publications and source records attributed to Victor F. Labson.

8 recordsLinked to original sources

USGS2020

The Modern Geological Survey; a model for research, innovation, synthjesis: A USGS perspective

Geological Surveys have long filled the role of providing Earth system science data and knowledge. These functions are increasingly complicated by accelerating environmental and societal change. Here we describe the USGS response to these evolving conditions. Underpinning the USGS approach is the recognition that many of the issues facing the U.S. and the world involve the interaction among geologic, hydrologic, and biologic processes, and how these interactions in turn affect society. Therefore, a goal of USGS planning is fostering interdisciplinary science. This focus is occurring in part through implementation of the recommendations of strategic planning teams. The USGS has also put in place groups building a broad information technology infrastructure as well as identifying and disseminating new Earth science research tools. In addition, the USGS has established an analysis and synthesis center that brings together groups of scientists who address interdisciplinary Earth system science issues. The goal is for these building blocks to evolve towards a comprehensive USGS data and knowledge platform; EarthMAP (Earth Monitoring, Assessment, and Projection). We also recognize that the modern geological survey must be a member of a community of geological surveys contributing data to a global database of 3-dimensional biogeophysical observations and interpretations.

Book chapter↗

USGS2017

Grand challenges for integrated USGS science — A workshop report

Executive Summary The U.S. Geological Survey (USGS) has a long history of advancing the traditional Earth science disciplines and identifying opportunities to integrate USGS science across disciplines to address complex societal problems. The USGS science strategy for 2007–2017 laid out key challenges in disciplinary and interdisciplinary arenas, culminating in a call for increased focus on a number of crosscutting science directions. Ten years on, to further the goal of integrated science and at the request of the Executive Leadership Team (ELT), a workshop with three dozen invited scientists spanning different disciplines and career stages in the Bureau convened on February 7–10, 2017, at the USGS John Wesley Powell Center for Analysis and Synthesis in Fort Collins, Colorado. The workshop focused on identifying “grand challenges” for integrated USGS science. Individual participants identified nearly 70 potential grand challenges before the workshop and through workshop discussions. After discussion, four overarching grand challenges emerged: Natural resource security, Societal risk from existing and emerging threats, Smart infrastructure development, and Anticipatory science for changing landscapes. Participants also identified a “comprehensive science challenge” that highlights the development of integrative science, data, models, and tools—all interacting in a modular framework—that can be used to address these and other future grand challenges: Earth Monitoring, Analyses, and Projections (EarthMAP) EarthMAP is our long-term vision for an integrated scientific framework that spans traditional scientific boundaries and disciplines, and integrates the full portfolio of USGS science: research, monitoring, assessment, analysis, and information delivery. The Department of Interior, and the Nation in general, have a vast array of information needs. The USGS meets these needs by having a broadly trained and agile scientific workforce. Encouraging and supporting cross-discipline engagement would position the USGS to tackle complex and multifaceted scientific and societal challenges in the 21st Century.

Open-File Report↗

USGS2012

Preliminary velocity and resistivity models of the Loma Prieta Earthquake region

A preliminary three-dimensional velocity model of the Loma Prieta epicentral region in the Santa Cruz Mountains of California has been derived using raypaths from aftershocks recorded by the U.S.G.S. seismic network. In addition, a magnetotelluric sounding profile was completed prior to the earthquake and a two-dimensional resistivity model computed. The velocity and resistivity models include a low-resistivity (3–10 ohm-m), low-velocity (3.3–5.8 km/s) wedge of material between the Zayante and San Andreas faults that extends to depths of over 8 km and is interpreted to be largely Tertiary marine sedimentary rocks. A high-resistivity (>1000 ohm-m), high-velocity (6.4–6.7 km/s) zone between the San Andreas and Sargent faults may represent largely mafic intrusive rocks.

California↗

USGS2011

Unique U.S. magnetic anomaly data base forthcoming

The year 2004 will offer an exciting and cost-effective opportunity to acquire a new U.S. magnetic anomaly data base. High Altitude Mapping Missions Inc. (HAMM) is currently planning an airborne mission to collect high-resolution Interferometric Synthetic Aperture Radar (IFSAR) imagery at an altitude of about 15 km, with a flight-line spacing of about 14 km over the conterminous United States and Alaska. Total and vector magnetic field data will also be collected with a “piggy-back” magnetometer system as a secondary mission objective. Because HAMM would fund the main flight costs of the mission, the geomagnetic community would acquire invaluable magnetic data at a nominal cost. These unique data will provide new insights on fundamental tectonic and thermal processes and give a new view of the structural and lithologic framework of continental areas and offshore regions.

Eos Science News↗

USGS2010

Estimated minimum discharge rates of the Deepwater Horizon spill— Interim report to the flow rate technical group from the Mass Balance Team

All of the calculations and results in this report are preliminary and intended for the purpose, and only for the purpose, of aiding the incident team in assessing the extent of the spilled oil for ongoing response efforts. Other applications of this report are not authorized and are not considered valid. Because of time constraints and limitations of data available to the experts, many of their estimates are approximate, are subject to revision, and certainly should not be used as the Federal Government's final values for assessing volume of the spill or its impact to the environment or to coastal communities. Each expert that contributed to this report reserves the right to alter his conclusions based upon further analysis or additional information. An estimated minimum total oil discharge was determined by calculations of oil volumes measured as of May 17, 2010. This included oil on the ocean surface measured with satellite and airborne images and with spectroscopic data (129,000 barrels to 246,000 barrels using less and more aggressive assumptions, respectively), oil skimmed off the surface (23,500 barrels from U.S. Coast Guard [USCG] estimates), oil burned off the surface (11,500 barrels from USCG estimates), dispersed subsea oil (67,000 to 114,000 barrels), and oil evaporated or dissolved (109,000 to 185,000 barrels). Sedimentation (oil captured from Mississippi River silt and deposited on the ocean bottom), biodegradation, and other processes may indicate significant oil volumes beyond our analyses, as will any subsurface volumes such as suspended tar balls or other emulsions that are not included in our estimates. The lower bounds of total measured volumes are estimated to be within the range of 340,000 to 580,000 barrels as of May 17, 2010, for an estimated average minimum discharge rate of 12,500 to 21,500 barrels per day for 27 days from April 20 to May 17, 2010.

Louisiana↗

USGS2003

Helicopter electromagnetic and magnetic survey data and maps, Seco Creek area, Medina and Uvalde counties, Texas

A helicopter electromagnetic and magnetic (HEM) survey was completed of a 209 square kilometer (81 square miles) area of the central Edwards aquifer. This open-file report is a release of the airborne geophysical data and a summary of the hydrologic application. The survey area was centered on the Valdina Farms sinkhole along the Seco Creek drainage in western Medina County, Texas. Flight lines were flown north south with three east west tie lines to aid in leveling the magnetic data. Additional lines were flown on each side of the Seco and Little Seco Creek drainages. A five kilometer (4 mile) extension of 15 lines was flown north of the main survey block centered on Seco Creek. This digital data release contains the flight line data, grids, and maps of the HEM survey data. The Edwards aquifer in this area consists of three hydrologic zones: catchment, recharge, and confined. The Glen Rose Formation is exposed in the catchment area. The recharge zone is situated in the Balcones fault zone where the Devils River Group of the Edwards aquifer has been exposed by normal faults. The magnetic data is not discussed in depth here, but does have high amplitude closed anomalies caused by shallow igneous intrusives. The Woodard Cave Fault that separates the recharge and catchment zones is in places associated with a weak linear magnetic low. The HEM data has been processed to produce apparent resistivities for each of the six EM coil pairs and frequencies. Maps of the apparent resistivity for the five horizontal coil pairs show that the catchment, recharge, and confined zones all have numerous linear features that are likely caused by structures, many of which have not been mapped. The distribution of high resistivity areas reflects the lithologic differences within the Trinity and Edwards aquifers.

Texas↗

USGS1990

The Denali fault system and Alaska Range of Alaska: Evidence for underplated Mesozoic flysch from magnetotelluric surveys

Regional magnetotelluric surveys recently completed across the central and eastern Alaska Range of Alaska provide evidence for large volumes of conductive rocks beneath the core of the range. These conductive rocks may represent a formerly extensive, but now collapsed, Mesozoic flysch basin formed on the leading edge of the Talkeetna superterrane (amalgamated Wrangellia, Peninsular, and Alexander terranes). The docking of the Talkeetna superterrane caused large-scale oblique thrusting, folding, and metamorphism in the flysch basin, and formation of a megasuture along which the Cenozoic strike-slip Denali fault system developed. The deep magnetotelluric soundings and seismic reflection data suggest the possibility that the highly conductive rocks were tectonically emplaced beneath the thin crystalline sheet constituting the southern Yukon-Tanana terrane over a broad region of the Alaska Range. The conductive rocks are locally correlated with surface outcrops of Mesozoic black shales that are part of Upper Jurassic and Cretaceous flysch but may be composed of Paleozoic carbonaceous shales as well. In either case, their extremely low resistivities make them a valuable marker horizon for tectonic studies. The conductive rocks are interpreted to extend to depths of greater than 20 km and were mapped north and northeast of the Denali fault for more than 50 km. The magnetotelluric surveys represent the first large-scale surveys done in Alaska, but the structures mapped are similar to those observed in large, compressed flysch basins in the eastern Alps and Carpathian Mountains of Europe. The results of these surveys bear on several key tectonic questions, including development of the ancestral Denali fault, and collapse and possible underplating of an extensive Mesozoic flysch system and associated igneous arc.

Alaska↗

USGS1987

Natural-field and very low-frequency tipper profile interpretation of contacts

Anomalous vertical magnetic field (tipper) profiles acquired using natural or very low-frequency (VLF) radio transmitter sources can be interpreted simply and rapidly for a number of geologic settings. The relations between computed numerical models, and outcropping dipping and buried vertical contacts are presented here in a series of interpretation charts. Use of the tipper phase in the analysis minimizes the effect of transmitter azimuth in the VLF case.Two examples illustrate the application to field data. An audiofrequency natural-field tipper profile over a conductive bed in a north-central Washington State metasedimentary sequence demonstrates the interpretation procedure for a dipping contact. VLF profiles over covered basement faults in Ontario demonstrate the application for a buried vertical contact. In both cases the quick results are in agreement with the much more laborious trial-and-error matching to two-dimensional models.

Geophysics↗