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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Basement Fault Activation before Larger Earthquakes in Oklahoma and Kansas

Oklahoma and Kansas experienced unprecedented seismic activity over the past decade due to earthquakes associated with unconventional hydrocarbon development. The modest natural seismicity and incomplete knowledge of the fault network in the region made it difficult to anticipate the locations of earthquakes with larger magnitudes (M w ≥ 4). Here, we show that monitoring of microearthquakes at regional scale using a pretrained neural phase picker and an earthquake relocation algorithm can illuminate unknown fault structures, and deliver information that can be synthesized for earthquake forecasting. We found that 80% of the larger earthquakes that occurred in the past decade could have been anticipated based on the spatial extent of the seismicity clusters that were formed before these earthquakes occurred. We also found that once a seismicity cluster with a length scale enough to host a larger earthquake was formed, there was a ~5% chance that it would host one or more larger earthquakes within a year. This probability is nearly an order of magnitude higher than one based on Gutenberg–Richter statistics and preceding seismicity. Applying our approach in practice can provide critical information on seismic hazards for risk management and regulatory decision making.

58 GEOSCIENCES↗
NASA NTRS1981

Structure of the midcontinent basement. Topography, gravity, seismic, and remote sensing

Some 600,000 discrete Bouguer gravity estimates of the continental United States were spatially filtered to produce a continuous tone image. The filtered data were also digitally painted in color coded form onto a shaded relief map. The resultant image is a colored shaded relief map where the hue and saturation of a given image element is controlled by the value of the Bouguer anomaly. Major structural features (e.g., midcontinent gravity high) are readily discernible in these data, as are a number of subtle and previously unrecognized features. A linear gravity low that is approximately 120 to 150 km wide extends from southeastern Nebraska, at a break in the midcontinent gravity high, through the Ozark Plateau, and across the Mississippi embayment. The low is also aligned with the Lewis and Clark lineament (Montana to Washington), forming a linear feature of approximately 2800 km in length. In southeastern Missouri the gravity low has an amplitude of 30 milligals, a value that is too high to be explained by simple valley fill by sedimentary rocks.

Guinness, E. A.↗
NASA NTRS1986

The western Wabigoon Subprovince, Superior Province, Canada: Archean greenstone succession in rifted basement complex

The Wabigoon Subprovince, interposed between the predominantly metasedimentary-plutonic and gneissic English River and Quetico Subprovinces to the north and south respectively, exposed Archean greenstone and granitoid rocks for a strike length of greater than 700 km. Based on predominating rock types, the western part of the subprovince is divided into two terrains: the northern Wabigoon volcano-sedimentary and pluonic terrain (NWW) and the Wabigoon Diapiric Axis terrain (WDA). Both the NWW and WDA are described according to volcanic sequence, geological faults, chemical composition and evolutionary history.

Edwards, G. R.↗
NASA NTRS1986

Sr, Nd, and Pb isotopes in Proterozoic intrusives astride the Grenville Front in Labrador - Implications for crustal contamination and basement mapping

Trace element and Pb, Sr, and Nd isotopic compositions of anorthosites and related rocks, and of younger mafic dikes from Harp Lake and Mealy Mountains in Labrador, Canada are estimated and compared. The effects of crustal component contaminants on the isotopic compositions of the dikes are investigated. The correlation between the isotopic data and the crustal contamination model is studied. It is observed that for Harp Lake the initial Sr ratios are higher and the Nd values are lower than Mealy samples, and the data do not correspond to the crustal contamination model; however, the Pb isotope data favor a crustal contamination model. It is noted that the Labrador segment of the Grenville Front appears to coincide with the southern margin of the Archean North Atlantic craton, and may represent a pre mid-Proterozoic suture.

Ashwal, L. D.↗
NASA NTRS1989

Lithology and structure within the basement terrain adjacent to Clark Mountains, California, mapped with calibrated data from the airborne visible/infrared imaging spectrometer

The Clark Mountains in eastern California form a rugged, highly dissected area nearly 5000 ft above sea level, with Clark Mountain rising to 8000 ft. The rocks of the Clark Mountains and the Mescal Range just to the south are Paleozoic carbonate and clastic rocks, and Mesozoic clastic and volcanic rocks standing in pronounced relief above the fractured Precambrian gneisses to the east. The Permian Kaibab Limestone and the Triassic Moenkopi and Chinle Formations are exposed in the Mescal Range, which is the only place in California where these rocks, which are typical of the Colorado Plateau, are found. To the west, the mountains are bordered by the broad alluvial plains of Shadow Valley. Cima Dome, which is an erosional remnant carved on a batholithic intrusion of quartz monzonite, is found at the south end of the valley. To the east of the Clark and Mescal Mountains is found the Ivanpah Valley, in the center of which is located the Ivanpah Play. Studies of the Clark Mountains with the airborne visible/infrared imaging spectrometer are briefly described.

Green, Robert O.↗
DOE OSTI2023

Basement rock hybrid drilling

A method for monitoring and controlling a downhole pressure of a well during formation of a borehole of a well is provided. The method can include monitoring a downhole pressure of a well during formation of a borehole of the well using a millimeter wave drilling apparatus including a waveguide configured for insertion into the borehole. The monitoring can include determining the downhole pressure. The downhole pressure can include an amount of pressure present at a bottom of the well. The method can also include determining a lithostatic pressure of rock surrounding the well at the bottom of the well. The method can further include controlling the downhole pressure relative to the lithostatic pressure of the rock surrounding the well at the bottom of the well. Related systems performing the methods are also provided.

Araque, Carlos↗
DOE OSTI2023

Basement rock hybrid drilling

A system for monitoring borehole parameters and switching to millimeter wave drilling based on the borehole parameters is provided. The system can include a mechanical drilling apparatus for forming a first portion of a borehole of a well. The first portion of the borehole can be formed based on a permeability of the first portion of the borehole and a temperature within the first portion of the borehole. The system can also include a millimeter wave drilling apparatus configured to inject millimeter wave radiation energy into a second portion of the borehole of the well via a waveguide. The second portion of the borehole can be formed via the millimeter wave drilling apparatus in response to determining the permeability of the first portion of the borehole is below a permeability threshold value and the temperature within the first portion of the borehole exceeds a temperature threshold value.

Araque, Carlos↗
DOE OSTI2023

Basement rock hybrid drilling

A system for monitoring and controlling downhole pressure of a well borehole relative to a lithostatic pressure of rock surrounding the borehole is provided. The system can include a millimeter wave drilling apparatus including a gyrotron configured to inject millimeter wave radiation energy into a borehole of a well via a waveguide configured for insertion into the borehole. The borehole can be formed via the millimeter wave drilling apparatus and having a downhole pressure monitored at a bottom of the well. The system can also include a compressor fluidically coupled to the borehole and configured to control the downhole pressure via a gas supplied into and/or received from the borehole. The compressor can be configured to control the downhole pressure relative to a lithostatic pressure determined for rock surrounding the well at the bottom of the well.

Araque, Carlos↗
DOE OSTI2023

Thermally Significant Fluid Seepage Through Thick Sediment on the Juan de Fuca Plate Entering the Cascadia Subduction Zone

We use heat flux measurements colocated with seismic reflection profiles over a buried basement high on the Juan de Fuca plate ∼25 km seaward of the deformation front offshore Oregon to test for the presence of hydrothermal circulation in the oceanic crust. We also revisit heat flux data crossing a buried basement high ∼25 km seaward of the deformation front ∼150 km north, offshore Washington. Seafloor heat flux is inversely correlated with sediment thickness, consistent with vigorous hydrothermal circulation in the basement aquifer homogenizing temperatures at the top of the basement. Heat flux immediately above the summit of the basement highs is greater than expected solely from conduction. Fluid seepage at rates of ∼2.6–5.4 cm yr −1 in a 1–1.5 km-wide conduit through ∼800–1,300 m thick sediment sections above these basement highs can explain these observations. Observations of thermally significant fluid seepage through sediment >225 m thick on oceanic crust are unprecedented. High sediment permeability, high fluid overpressure in the basement, or a combination of both is required to drive fluid seepage at the observed rates. We infer that rapid seepage occurs because the basement highs rise above the low permeability basal sediment with their tops protruding into the base of high permeability Nitinat or Astoria Fan sediment. Seepage from basement highs penetrating into the submarine fans can affect the thermal state of crust entering the subduction zone.

58 GEOSCIENCES↗
DOE OSTI2025

E-Area Low-Level Waste Facility Inadvertent Human Intruder Limits and Doses in Support of the PA2022

This report documents the inadvertent human intruder (IHI) analysis for the E-Area Low-Level Waste Facility (ELLWF) at the Savannah River Site (SRS), near Aiken, South Carolina. This analysis supports the revised ELLWF Performance Assessment (PA), complying with the Department of Energy standard for operation of low-level waste disposal facilities (USDOE, 2017). The ELLWF is an operating waste disposal facility and is scheduled to continue accepting waste to 2065. One task of the revised PA is to establish waste inventory limits for the various disposal units at ELLWF. This is done by modeling future contaminant release and transport through applicable pathways to human receptors, comparing predicted doses per disposed curie with applicable performance measures, to obtain inventory limits which will assure that doses to receptors do not exceed performance measures. This report documents results of modeling future doses to one class of receptor, the inadvertent human intruder. It is assumed that after site closure, public knowledge of the site is lost, and IHIs will engage in activities on the ELLWF that will disrupt the closure cap, causing dose to the IHI. Following USDOE (2017), six different stylized exposure scenarios are considered, simulating activities by an IHI which could result in a radiological dose. The six scenarios are: • Acute – Basement Construction: IHI constructs a basement and encounters waste during excavation which is inadvertently mixed with clean soil and diluted. • Acute – Well Drilling: IHI drills a water well through waste and is exposed to drill cuttings mixed with clean soil that are brought to the surface. • Acute – Discovery: IHI begins constructing a basement but stops when encountering the riprap in the final closure cap and is exposed to photon radiation from unexcavated material residing in the undisturbed waste zone. • Chronic – Agriculture: Resident IHI is exposed to waste that was excavated for basement construction and mixed with native soil in the intruder’s vegetable garden. • Chronic – Post-Drilling: Resident IHI is exposed to waste from drill cuttings mixed with native soil and scattered in the garden area. • Chronic – Residential: Resident IHI is exposed to external radiation while in home located above waste with shielding provided by the concrete basement floor and any soil or engineered material remaining between the basement and waste. Dose calculations are performed using the SRNL Dose Toolkit (Aleman, 2023), following the approach of Smith et al (2019). Calculations are performed separately for 27 of the 33 disposal units (DUs) at ELLWF and are radionuclide specific. The results of the IHI analysis include: • Dose Factors: mrem per disposed curie (acute) and mrem/yr per disposed curie (chronic) for each parent radionuclide, for each DU. • Inventory Limits: in curies, for each parent radionuclide, for each DU. • Estimated Dose to IHI: mrem (acute) and mrem/yr (chronic), for each DU, given its projected closure inventory without inventory biases applied. Most DU-specific IHI inventory limits are in the range of 10 3 to 10 7 curies per nuclide. The lowest inventory limits are associated with gamma-emitters such as Sn-126, Ra-226, Th-232, and Cm-248. Radionuclides with short half-lives such as Pu-241, and nuclides which are pure beta emitters or which decay by electron capture, such as Ni-59 and Ni-63, have the highest limits. For the 27 evaluated DUs, predicted IHI doses are shown in Table ES-1. The maximum acute dose is 1.18 mrem, at ST23, much less than the DOE performance measure of 500 mrem (USDOE, 2017). The highest chronic dose is 37.2 mrem/yr at ST02, below the DOE performance measure of 100 mrem/yr. Also shown are estimated inventory sums of fractions (SOFs) at closure in 2065, for groundwater (GW) and IHI pathways. For each DU, the inventory is constrained by the GW pathway. For most DUs, the IHI SOFs are approximately 1000 times lower than the GW SOF values, and the IHI pathway does not drive risk for any disposal unit.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗