Depth to bedrock using gravimetry in the Reno and Carson City, Nevada, area basins

Geophysics ◽  
2000 ◽  
Vol 65 (2) ◽  
pp. 340-350 ◽  
Author(s):  
Robert E. Abbott ◽  
John N. Louie
Keyword(s):  
Urban Areas ◽  
Sedimentary Basins ◽  
Maximum Depth ◽  
Oil Well ◽  
Gravity Fields ◽  
Gravity Measurements ◽  
Geothermal Wells ◽  
Data Coverage ◽  
Western Side ◽  
Well Data

Sedimentary basins can trap earthquake surface waves and amplify the magnitude and lengthen the duration of seismic shaking at the surface. Poor existing gravity and well‐data coverage of the basins below the rapidly growing Reno and Carson City urban areas of western Nevada prompted us to collect 200 new gravity measurements. By classifying all new and existing gravity locations as on seismic bedrock or in a basin, we separate the basins’ gravity signature from variable background bedrock gravity fields. We find an unexpected 1.2-km maximum depth trough below the western side of Reno; basin enhancement of the seismic shaking hazard would be greatest in this area. Depths throughout most of the rest of the Truckee Meadows basin below Reno are less than 0.5 km. The Eagle Valley basin below Carson City has a 0.53-km maximum depth. Basin depth estimates in Reno are consistent with depths to bedrock in the few available records of geothermal wells and in one wildcat oil well. Depths in Carson City are consistent with depths from existing seismic reflection soundings. The well and seismic correlations allow us to refine our assumed density contrasts. The basin to bedrock density contrast in Reno and Carson City may be as low as −0.33 g/cm3. The log of the oil well, on the deepest Reno subbasin, indicates that Quaternary deposits are not unusually thick there and suggests that the subbasin formed entirely before the middle Pliocene. Thickness of Quaternary fill, also of importance for determining seismic hazard below Reno and Carson City may only rarely exceed 200 m.

Gravity Measurements of the Juno Spacecraft Matched with Jupiter Models that rely on a Dilute Core and Deep Winds

2021 ◽  
Author(s):  
Burkhard Militzer ◽  
Sean Wahl ◽  
William Hubbard
Keyword(s):  
Phase Separation ◽  
Inner Core ◽  
Interior Layer ◽  
Gravity Fields ◽  
Gravity Measurements ◽  
Theoretical Predictions

<div><span>Since its arrival at Jupiter in 2016, the Juno spacecraft has measured the planet’s gravity fields with unprecedented precision. The interpretation of these measurements has been challenging because the magnitudes of the gravity coefficients J</span><sub>4</sub><span> and J</span><sub>6</sub><span> were smaller than predicted by traditional interiors models that included a dense inner core composed of rock and ice. Here we instead present models with dilute cores [Geophys. Res. Lett. 44 (2017) 4649] and deep-winds that conform to theoretical predictions of hydrogen-helium phase separation in the interior layer from approximately 0.8 to 0.85 Jupiter radii. Such models match the entire set of zonal gravity measurements by the Juno spacecraft. Our work is based on the accelerated version of the Concentric Maclaurin Spheroid method [Astrophysical J. </span><strong>879</strong><span> (2019) 78]. We conclude by comparing with models for Saturn’s interior. </span></div>

The 2018 update of the US National Seismic Hazard Model: Overview of model and implications

2019 ◽  
Vol 36 (1) ◽  
pp. 5-41 ◽  
Author(s):  
Mark D. Petersen ◽  
Allison M. Shumway ◽  
Peter M. Powers ◽  
Charles S. Mueller ◽  
Morgan P. Moschetti ◽  
...  
Keyword(s):  
United States ◽  
Los Angeles ◽  
Seismic Hazard ◽  
San Francisco ◽  
Urban Areas ◽  
Salt Lake ◽  
Sedimentary Basins ◽  
Hazard Model ◽  
Eastern United States ◽  
Ground Shaking

During 2017–2018, the National Seismic Hazard Model for the conterminous United States was updated as follows: (1) an updated seismicity catalog was incorporated, which includes new earthquakes that occurred from 2013 to 2017; (2) in the central and eastern United States (CEUS), new ground motion models were updated that incorporate updated median estimates, modified assessments of the associated epistemic uncertainties and aleatory variabilities, and new soil amplification factors; (3) in the western United States (WUS), amplified shaking estimates of long-period ground motions at sites overlying deep sedimentary basins in the Los Angeles, San Francisco, Seattle, and Salt Lake City areas were incorporated; and (4) in the conterminous United States, seismic hazard is calculated for 22 periods (from 0.01 to 10 s) and 8 uniform VS30 maps (ranging from 1500 to 150 m/s). We also include a description of updated computer codes and modeling details. Results show increased ground shaking in many (but not all) locations across the CEUS (up to ~30%), as well as near the four urban areas overlying deep sedimentary basins in the WUS (up to ~50%). Due to population growth and these increased hazard estimates, more people live or work in areas of high or moderate seismic hazard than ever before, leading to higher risk of undesirable consequences from forecasted future ground shaking.

scholarly journals Seismological Investigations in the Olduvai Basin and Ngorongoro Volcanic Highlands (Western Flank of the North Tanzanian Divergence)

2020 ◽  
Vol 91 (6) ◽  
pp. 3286-3303 ◽  
Author(s):  
Laura Parisi ◽  
Ian Stanistreet ◽  
Jackson Njau ◽  
Kathy Schick ◽  
Nicholas Toth ◽  
...  
Keyword(s):  
Sedimentary Basins ◽  
Quality Analysis ◽  
Fault System ◽  
Conservation Area ◽  
Data Set ◽  
The North ◽  
Western Flank ◽  
Passive Seismic ◽  
African Rift ◽  
Western Side

Abstract We present data and results of a passive seismic experiment that we operated between June 2016 and May 2018 in the Ngorongoro Conservation Area (northern Tanzania), located on the western side of the eastern branch of the Eastern African Rift (EAR) system. The motivation for this experiment is twofold: (1) investigating the extension of the Olduvai basin, referred to also as the “Cradle of Human Mankind,” as it hosted a variety of paleoenvironments exploited by hominins during their evolution; and (2) studying the link between the fault system in the main EAR and in its western flank. We conduct detailed data-quality analysis of the seismic recordings based upon ambient noise characterization and numerical waveform simulations. Our data set is of good quality, and we observe that local magnitude can be overestimated up to at least 0.23, due to wave-amplifications effects occurring at sites with loose sedimentary material. Based on a new but simple approach using power spectral density measurements, we calculate the thickness of sedimentary basins. This allows us to map the bottom of the Olduvai paleolake confirming that its sedimentary record may be at least 200 m deeper than previously inferred from core drilling. We also map the bottom of the Olbalbal depression for the first time. In addition, we present a seismicity map of the Ngorongoro Conservation Area with unprecedented detail. The seismicity depicts the suture zone between the Tanzanian craton and the Mozambique belt and reveals that the fault system in the western flank of the rift merges at depth into a single detachment that joins the Manyara fault on the western side of the main rift valley.

scholarly journals An Investigation of Seismic Velocity Variation through a Tectonic Boundaries-Case Study in Central Iraq

2021 ◽  
pp. 2614-2626
Author(s):  
Ahmed S. AL-Banna ◽  
Hassan E. Al-Assady
Keyword(s):  
High Velocity ◽  
Seismic Velocity ◽  
Velocity Model ◽  
Seismic Inversion ◽  
Velocity Variation ◽  
Time Model ◽  
3D Velocity Model ◽  
Western Side ◽  
Well Data ◽  
Seismic Lines

      A 3D velocity model was created by using stacking velocity of 9 seismic lines and average velocity of 6 wells drilled in Iraq. The model was achieved by creating a time model to 25 surfaces with an interval time between each two successive surfaces of about 100 msec.  The summation time of all surfaces reached about 2400 msec, that was adopted according to West Kifl-1 well, which penetrated to a depth of 6000 m, representing the deepest well in the study area. The seismic lines and well data were converted to build a 3D cube time model and the velocity was spread on the model. The seismic inversion modeling of the elastic properties of the horizon and well data was applied to achieve a corrected velocity cube. Then, the velocity cube was converted to a time model and, finally, a corrected 3D depth model was obtained. This model shows that the western side of the study area, which is a part of the stable shelf, is characterized by relatively low thickness and high velocity layers. While the eastern side of the study area, which is a part of the Mesopotamian, is characterized by high thickness and low velocity of the Cretaceous succession. The Abu Jir fault is considered as a boundary between the stable and unstable shelves in Iraq, situated at the extreme west part of the study area. The area of relatively high velocity gradient is considered as the limit of the western side of the Mesopotamian basin. This area extends from Najaf-Karbala axis in the west to the Euphrates River in the east. It is found that the 3D stacking velocity model can be used to obtain good results concerning the tectonic boundary.  

scholarly journals Linking zonal winds and gravity: the relative importance of dynamic self-gravity

2020 ◽  
Vol 492 (3) ◽  
pp. 3364-3374 ◽  
Author(s):  
Johannes Wicht ◽  
Wieland Dietrich ◽  
Paula Wulff ◽  
Ulrich R Christensen
Keyword(s):  
Zonal Flow ◽  
Order Effect ◽  
Radial Dependence ◽  
Spherical Harmonic Degree ◽  
Zonal Flows ◽  
Gravity Fields ◽  
Gravity Measurements ◽  
Density Perturbations ◽  
Self Gravity ◽  
The Impact

ABSTRACT Recent precise measurements of Jupiter’s and Saturn’s gravity fields help constraining the properties of the zonal flows in the outer envelopes of these planets. The link is provided by a simplified dynamic equation, which connects zonal flows to related buoyancy perturbations. These can result from density perturbations but also from the gravity perturbations. Whether the latter effect, which we call dynamic self-gravity (DSG), must be included or is negligible has been a matter of intense debate. We show that the second-order differential equation for the gravity perturbations becomes an inhomogeneous Helmholtz equation when assuming a polytrope of index unity for density and pressure. This equation can be solved semi-analytically when using modified spherical Bessel functions for describing the radial dependence. The respective solutions allow us to quantify the impact of the DSG on each gravity harmonic, practically independent of the zonal flow or the details of the planetary interior model. We find that the impact decreases with growing spherical harmonic degree ℓ. For degrees ℓ = 2 to about ℓ = 4, the DSG is a first-order effect and should be taken into account in any attempt of inverting gravity measurements for zonal flow properties. For degrees of about ℓ = 5 to roughly ℓ = 10, the relative impact of DSG is about 10 per cent and thus seems worthwhile to include, in particular since this comes at little extra cost with the method presented here. For yet higher degrees, it seems questionable whether gravity measurements or interior models will ever reach the precision required for disentangling the small DSG effects, which amount to only a few per cent at best.

Full Reproduction of Surface Dynamometer Card Based on Periodic Electric Current Data

2021 ◽  
pp. 1-10
Author(s):  
Dandan Zhu ◽  
Xiaoting Luo ◽  
Zhanmin Zhang ◽  
Xiangyi Li ◽  
Gao Peng ◽  
...  
Keyword(s):  
Short Term Memory ◽  
Current Method ◽  
Current Data ◽  
Oil Well ◽  
Financial Investment ◽  
Pumping System ◽  
The Mean ◽  
Lstm Network ◽  
Well Data ◽  
Dynamometer Card

Summary The surface dynamometer card is composed of ground load and ground displacement, which is of great significance to reflect the operation of rod pumping and the exploitation of crude oil. However, the current method of obtaining the surface dynamometer by sensors is a huge financial investment on the sensor installations and maintenance. In this paper, we propose an innovative method based on deep learning to reproduce the surface dynamometer card directly from electrical parameters. In our method, the convolution neural network is used as the basic layer to automatically extract the spatial characteristics of input data. A long short-term memory (LSTM) network as the core component is used for the output layer to consider the time dependence of the dynamometer card. Finally, the experimental shows that the proposed method achieves the mean relative error (MRE) of 4.00% on the real oil well data in A-oilfield, and the dynamometer card calculated by our model is basically consistent with the field data. In addition, the method has been tested in new wells with a rod pumping system, and the results show that the accuracy of the model is close to 90%, which has already greatly outperformed the previous methods.

scholarly journals Mechanisms of overburden deformation associated with the emplacement of the Tulipan sill, mid-Norwegian margin

2017 ◽  
Vol 5 (3) ◽  
pp. SK23-SK38 ◽  
Author(s):  
Tobias Schmiedel ◽  
Sigurd Kjoberg ◽  
Sverre Planke ◽  
Craig Magee ◽  
Olivier Galland ◽  
...  
Keyword(s):  
Host Rock ◽  
Shear Failure ◽  
Sedimentary Basins ◽  
Rock Deformation ◽  
3D Seismic ◽  
Elastic Bending ◽  
Hydrocarbon Maturation ◽  
Dome Structure ◽  
Well Data ◽  
Host Rocks

The emplacement of igneous intrusions into sedimentary basins mechanically deforms the host rocks and causes hydrocarbon maturation. Existing models of host-rock deformation are investigated using high-quality 3D seismic and industry well data in the western Møre Basin offshore mid-Norway. The models include synemplacement (e.g., elastic bending-related active uplift and volume reduction of metamorphic aureoles) and postemplacement (e.g., differential compaction) mechanisms. We use the seismic interpretations of five horizons in the Cretaceous-Paleogene sequence (Springar, Tang, and Tare Formations) to analyze the host rock deformation induced by the emplacement of the underlying saucer-shaped Tulipan sill. The results show that the sill, emplaced between 55.8 and 54.9 Ma, is responsible for the overlying dome structure observed in the seismic data. Isochron maps of the deformed sediments, as well as deformation of the younger postemplacement sediments, document a good match between the spatial distribution of the dome and the periphery of the sill. The thickness [Formula: see text] of the Tulipan is less than 100 m, whereas the amplitude [Formula: see text] of the overlying dome ranges between 30 and 70 m. Spectral decomposition maps highlight the distribution of fractures in the upper part of the dome. These fractures are observed in between hydrothermal vent complexes in the outer parts of the dome structure. The 3D seismic horizon interpretation and volume rendering visualization of the Tulipan sill reveal fingers and an overall saucer-shaped geometry. We conclude that a combination of different mechanisms of overburden deformation, including (1) elastic bending, (2) shear failure, and (3) differential compaction, is responsible for the synemplacement formation and the postemplacement modification of the observed dome structure in the Tulipan area.

scholarly journals Pleasant Bayou Geopressured-Geothermal Reservoir Analysis—October 1991

1992 ◽  
Vol 114 (4) ◽  
pp. 315-322 ◽  
Author(s):  
T. D. Riney
Keyword(s):  
Gulf Coast ◽  
Sedimentary Basins ◽  
Department Of Energy ◽  
Well Test ◽  
Deep Wells ◽  
Geological Information ◽  
Fluid Properties ◽  
Southeast Texas ◽  
Reservoir Simulation Model ◽  
Well Data

Many sedimentary basins contain formations with pore fluids at pressures higher than hydrostatic value; these formations are called geopressured. The pore pressure is generally well in excess of hydrostatic and the fluids are saline, hot, and contain dissolved methane. The U.S. Department of Energy (DOE) has drilled and tested deep wells in the Texas-Louisiana Gulf Coast region to evaluate the geopressured-geothermal resource. Geological information for the Pleasant Bayou geopressured resource in southeast Texas is most extensive among the reservoirs tested. Testing of the DOE well (Pleasant Bayou No. 2) was conducted during 1979–1983; testing resumed in May 1988. A numerical simulator is employed to synthesize and integrate the geological information, formation rock and fluid properties data from laboratory tests, and well data from the earlier (1979–1983) and the ongoing testing (1988–1991) of the well. A reservoir simulation model has been constructed which provides a detailed match to the well test history to date.

Sign in / Sign up

Export Citation Format

Share Document