Subsurface Geometry and Emplacement Conditions of a Giant Dike System in Elysium Fossae, Mars

2020 ◽  
Author(s):  
Sam Rivas‐Dorado ◽  
Javier Ruiz ◽  
Ignacio Romeo
Keyword(s):  
Subsurface Geometry

Fault Attitude of the North Section of Huangzhuang-Gaoliying Fault at Beijing, China and Its Effects on the Ground Rupture

2019 ◽  
Vol 24 (4) ◽  
pp. 549-555
Author(s):  
Shuai Zhao ◽  
Yongqi Meng ◽  
Zhenning Ma ◽  
Jiajun Sun
Keyword(s):  
Human Life ◽  
Geophysical Methods ◽  
Beijing Area ◽  
The North ◽  
Refraction Tomography ◽  
Surface Ruptures ◽  
Earthquake Faults ◽  
Subsurface Geometry ◽  
Seismic Images ◽  
Beijing China

Worldwide, slip on earthquake faults causes numerous disasters, resulting in large losses in human life and built structures. To minimize future losses associated with earthquakes along such faults, it is important to precisely locate the faults relative to the built environment and to determine the subsurface geometry of the faults. In Beijing, China, we used shallow-depth geophysical methods to evaluate the location and subsurface geometry of the Huangzhuang-Gaoliying fault (HGF), one of the principal tectonic faults of Beijing area. We used seismic reflection and refraction tomography, multi-channel analysis of surface waves (MASW), and paleoseismic trenching to characterize the north section of HGF near the Gaoliying section of Beijing. Our seismic images indicated that there are at least two strands of the HGF that are distributed over an approximately 200-m-wide zone. We identified a principal fault strand (F1) that is observed in all the seismic images, as well as in a paleoseismic trench. The F1 strikes approximately N49°E and dips southeastward at 70° to 75°. Over the past few years, surface ruptures have occurred along the HGF in several locations, but it is unclear if the surface ruptures were the result of tectonic slip on the HGF or were related to land subsidence along the fault.

Tectonic significance of potential-field anomalies in western Canada: results from the Lithoprobe SNORCLE transect

2005 ◽  
Vol 42 (6) ◽  
pp. 1239-1255 ◽  
Author(s):  
C Elissa Lynn ◽  
Frederick A Cook ◽  
Kevin W Hall
Keyword(s):  
Cross Sections ◽  
Upper Mantle ◽  
Potential Field ◽  
Precambrian Rocks ◽  
Reflection And Refraction ◽  
Gravity And Magnetic ◽  
Tectonic Significance ◽  
Geometrical Constraints ◽  
Subsurface Geometry ◽  
Local Anomalies

Potential-field anomalies within the Lithoprobe SNORCLE (Slave – Northern Cordillera Lithospheric Evolution) transect area provide geometrical constraints for regional crustal and lithospheric structures, as well as for local anomalies when coupled with subsurface geometry visible on nearly 2500 km of deep seismic reflection and refraction profiles. Areal distribution of gravity and magnetic anomalies permit structures to be projected away from seismic cross sections, and forward modelling provides tests of different interpretations of deep (crustal and upper mantle) density structures. In a key result from modelling, a Paleoproterozoic subduction zone beneath the Wopmay orogen probably consists of high-density rocks, such as eclogite, within the upper mantle. This result supports the concept of moderate- to low-angle intra-lithospheric sutures. On an even larger scale, applications of bandpass and directional filters assist in detecting anomalies according to wavelength or azimuthal orientation and thus provide means to track patterns across structural grain. For example, gravity and magnetic trends that are associated with Precambrian rocks of the Canadian Shield can, in some cases, be followed across much of the Cordillera. This result is consistent with North American Precambrian rocks composing much of the crust in the Cordillera and thus that the addition of "new" lithosphere during Mesozoic – early Tertiary accretion has been relatively minor.

Joint inversion of full-waveform ground-penetrating radar and electrical resistivity data: Part 1

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. H97-H113 ◽  
Author(s):  
Diego Domenzain ◽  
John Bradford ◽  
Jodi Mead
Keyword(s):  
Electrical Conductivity ◽  
Electrical Resistivity ◽  
Ground Penetrating Radar ◽  
Joint Inversion ◽  
Geophysical Methods ◽  
Data Types ◽  
Full Waveform ◽  
Electrical Permittivity ◽  
Ground Penetrating ◽  
Subsurface Geometry

We have developed an algorithm for joint inversion of full-waveform ground-penetrating radar (GPR) and electrical resistivity (ER) data. The GPR data are sensitive to electrical permittivity through reflectivity and velocity, and electrical conductivity through reflectivity and attenuation. The ER data are directly sensitive to the electrical conductivity. The two types of data are inherently linked through Maxwell’s equations, and we jointly invert them. Our results show that the two types of data work cooperatively to effectively regularize each other while honoring the physics of the geophysical methods. We first compute sensitivity updates separately for the GPR and ER data using the adjoint method, and then we sum these updates to account for both types of sensitivities. The sensitivities are added with the paradigm of letting both data types always contribute to our inversion in proportion to how well their respective objective functions are being resolved in each iteration. Our algorithm makes no assumptions of the subsurface geometry nor the structural similarities between the parameters with the caveat of needing a good initial model. We find that our joint inversion outperforms the GPR and ER separate inversions, and we determine that GPR effectively supports ER in regions of low conductivity, whereas ER supports GPR in regions with strong attenuation.

Subsurface geometry and structural evolution of La Gomera island based on gravity data

2011 ◽  
Vol 199 (1-2) ◽  
pp. 105-117 ◽  
Author(s):  
Fuensanta González Montesinos ◽  
José Arnoso ◽  
Ricardo Vieira ◽  
Maite Benavent
Keyword(s):  
Gravity Data ◽  
Structural Evolution ◽  
Subsurface Geometry ◽  
La Gomera

Toward Seismic Microzonation—2-D Modeling and Ambient Seismic Noise Measurements: The Case of an Embanked, Deep Alpine Valley

2005 ◽  
Vol 21 (3) ◽  
pp. 635-651 ◽  
Author(s):  
Corine Frischknecht ◽  
Philippe Rosset ◽  
Jean-Jacques Wagner
Keyword(s):  
Resonant Frequency ◽  
Seismic Noise ◽  
Ambient Seismic Noise ◽  
Alpine Valley ◽  
Noise Measurements ◽  
Soil Site ◽  
Surficial Deposit ◽  
The One ◽  
Shape Ratio ◽  
Subsurface Geometry

In the Sion area of Switzerland, part of a deep, embanked sediment-filled valley, investigations on soil site effects have been conducted using two independent methods. Two-dimensional (2-D) modeling was performed with a program based on the Indirect Boundary Element Method (Pedersen et. al. 1994). Numerical simulations allow taking into account the subsurface geometry of the valley and its peculiar characteristics, such as a variable shape ratio and a high shear-wave velocity contrast. The H/V method has been applied on ambient seismic noise measurements recorded on sites as close as possible to the 2-D modeling. This technique allows capturing the fundamental resonant frequency of the deepest sediments as well as identifying the existence of a surficial deposit. Both approaches agree on the fact that the fundamental resonant frequency of the valley is below 1 Hz. The amplification level of the predominant frequency obtained with numerical simulation is up to two times higher than the one given by the H/V ratio. These results provide the basis for further investigations in order to resolve differences.

scholarly journals Recent faulting along Gorontalo fault based on seismicity data analysis and lineament mapping

2021 ◽  
Vol 325 ◽  
pp. 01013
Author(s):  
Hasan Arif Efendi ◽  
Gayatri Indah Marliyani ◽  
Subagyo Pramumijoyo
Keyword(s):  
Fault Scarp ◽  
Seismic Catalogue ◽  
Seismicity Distribution ◽  
Time Period ◽  
Shallow Earthquakes ◽  
Continuous Record ◽  
Surface Manifestation ◽  
Weak Surface ◽  
Lineament Analysis ◽  
Subsurface Geometry

We focused our study to characterize the geometry and activity of Gorontalo fault. We analysed reviewed the ISC seismic catalogue and the BMKG relocated earthquake events available for the time period of 1960 to 2021, located along the expected location of this fault. In addition, we analysed continuous record from local seismic observatory available for the same period. Further, we mapped the lineaments using 8.3-m resolution DEMNAS data. Tens on shallow earthquakes occurred in the vicinity of this fault with a range magnitude of M 2 to 3. Our lineament analysis however does not reveal distinctive pattern that may indicate the fault manifestation at the surface. The NW-SE trending lineaments are coincidence with the mapped trace of Gorontalo Fault. The weak surface manifestation of the fault scarp may be related to the tropical climatic condition of the area which may obliterate the faulting topography. However, we observed alignment of the seismicity distribution with the mapped NW-SE lineament, indicating that the lineament is likely representing active fault and these earthquakes are associated with faulting along this fault. Our study provide indication that the Gorontalo Fault is active and further study is necessary to investigate subsurface geometry and mitigate its seismic hazards.

Determining Grain Boundary Position and Geometry from EBSD Data: Limits of Accuracy

2021 ◽  
pp. 1-13
Author(s):  
David T. Fullwood ◽  
Sarah Sanderson ◽  
Sterling Baird ◽  
Jordan Christensen ◽  
Eric R. Homer ◽  
...  
Keyword(s):  
Electron Backscatter Diffraction ◽  
Finite Size ◽  
Sample Surface ◽  
Accurate Method ◽  
Crystalline Materials ◽  
Backscattered Electrons ◽  
Ebsd Data ◽  
Subsurface Geometry ◽  
Backscatter Diffraction ◽  
Transition Curves

As the feature size of crystalline materials gets smaller, the ability to correctly interpret geometrical sample information from electron backscatter diffraction (EBSD) data becomes more important. This paper uses the notion of transition curves, associated with line scans across grain boundaries (GBs), to correctly account for the finite size of the excitation volume (EV) in the determination of the geometry of the boundary. Various metrics arising from the EBSD data are compared to determine the best experimental proxy for actual numbers of backscattered electrons that are tracked in a Monte Carlo simulation. Consideration of the resultant curves provides an accurate method of determining GB position (at the sample surface) and indicates a significant potential for error in determining GB position using standard EBSD software. Subsequently, simple criteria for comparing experimental and simulated transition curves are derived. Finally, it is shown that the EV is too shallow for the curves to reveal subsurface geometry of the GB (i.e., GB inclination angle) for most values of GB inclination.

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