Testing a Local-Distance Rg/Sg Discriminant Using Observations from the Bighorn Region, Wyoming

2020 ◽  
Vol 110 (2) ◽  
pp. 727-741 ◽  
Author(s):  
Jonas A. Kintner ◽  
K. Michael Cleveland ◽  
Charles J. Ammon ◽  
Andrew Nyblade
Keyword(s):  
Sedimentary Basins ◽  
Site Amplification ◽  
Source Material ◽  
Spectral Amplitude ◽  
Single Shot ◽  
Mountainous Terrain ◽  
Geometrical Spreading ◽  
Propagation Models ◽  
Local Distance ◽  
Mine Blasts

ABSTRACT This study explores the effectiveness of local-distance (<200  km) seismic discriminant to distinguish between surface mine blasts, single-shot borehole explosions, and earthquakes in the Bighorn Mountains region, Wyoming. We focus on the ratio between local-distance fundamental-mode surface waves (Rg) and the crustal shear-wave (Sg) signals. The observed spectral amplitude measurements are fit to propagation models that account for distance-dependent geometrical spreading and attenuation, and site amplification factors. The results support previous observations that Rg attenuates rapidly, is amplified in sedimentary basins, and has suppressed amplitudes in isolated mountainous terrain. Sg attenuates less rapidly than Rg but exhibits a similar spatial site amplification pattern. We compute an Rg/Sg source discriminant by taking the ratio between site- and distance-corrected Rg and Sg amplitude measurements. The results suggest that the site- and distance-corrected Rg/Sg ratios can distinguish events larger than ML∼1.5 (in the Bighorn region). The discriminant may also be sensitive to explosion emplacement conditions, where the ratios are higher for borehole shots in sedimentary strata and lower for explosions within the basement. The analysis shows that the Rg/Sg discriminant is effective for events in the Bighorn region for events larger than ML∼1.5 if proper considerations are made to account for event size and near-source material.

Single-shot reconstruction of spectral amplitude and phase in a fiber ring cavity at a 80  MHz repetition rate

2016 ◽  
Vol 41 (20) ◽  
pp. 4641 ◽  
Author(s):  
Jonas Hammer ◽  
P. Hosseini ◽  
C. R. Menyuk ◽  
Philip St.J. Russell ◽  
Nicolas Y. Joly
Keyword(s):  
Repetition Rate ◽  
Ring Cavity ◽  
Spectral Amplitude ◽  
Single Shot ◽  
Fiber Ring

High-frequency Pn attenuation in the Canadian shield

1989 ◽  
Vol 79 (4) ◽  
pp. 1039-1053
Author(s):  
Kin-Yip Chun ◽  
Richard J. Kokoski ◽  
Gordon F. West
Keyword(s):  
Velocity Structure ◽  
Epicentral Distance ◽  
Spectral Amplitude ◽  
Common Source ◽  
Spatial Decay ◽  
Geometrical Spreading ◽  
Eastern Canada ◽  
Frequency Dependent ◽  
Low Frequencies ◽  
Head Waves

Abstract Frequency-dependent spatial attenuation of Pn waves, incorporating the combined effects of geometrical spreading and anelastic dissipation, is investigated in eastern Canada between 3 and 15 Hz. Measurement of this total attenuation, instead of the two separate effects, circumvents the usual need for making a priori assumptions regarding the Pn geometrical spreading rate. The data consist of 77 Pn spectra, all amplitude-normalized using a set of previously measured spectral ratios of eastern Canadian earthquake sources. The normalization procedure eliminates the need for explicit source spectral assumptions, another common source of error in Pn attenuation measurements. An unconventional technique is introduced to account for differences in observed Pn spectra, which arise from geological site effects and instrument response error, both of which are frequency-dependent phenomena. We conclude that, at each frequency, the Pn amplitude falls off with distance according to: Δ−n, where Δ is epicentral distance. The exponent n is weakly frequency-dependent and takes the form: 2.2 + 0.02f. A unique interpretation of the behavior of the Pn spectral amplitude decay is unattainable, owing to the difficulty in separating the effects due to anelastic dissipation and the velocity structure in the uppermost mantle. It is interesting to note, however, that the spatial decay of pure elastic head waves follows the classical Δ−1/2L−3/2 relation, where L is the distance the waves travel in the mantle refractor. For the distance range of our interest (260-1087 km), this amounts to Δ−2.2. This indicates that towards low frequencies our n approaches a value which is consistent with the spatial decay rate expected of pure elastic head waves.

scholarly journals Representing Absence: Contemporary Ekphrasis in “Apesh-t”

Text Matters ◽  
2020 ◽  
pp. 118-143
Author(s):  
Agata Handley
Keyword(s):  
Source Material ◽  
Music Videos ◽  
The Other ◽  
Visual Images ◽  
Single Shot ◽  
Cultural Resistance ◽  
Works Of Art ◽  
Jay Z ◽  
The Way

Traditionally, ekphrasis has been defined as the description and analysis of works of art in poetry, and so it has been understood as the verbalization of visual images (Sager Eidt). The article examines the concept in the light of contemporary definitions that include non-verbal media as targets (Cariboni Killander, Lutas and Strukelj; Sager Eidt; Bruhn; Pethö) in order to analyze its applicability to music videos. It concentrates in particular on “Apesh-t,” a video for a track by Beyoncé and Jay-Z from the album Everything Is Love (2018). The video is filmed in different interiors of the Louvre, where the singers appear, together with an ensemble of dancers, in front of selected artworks. The discussion focuses on an analysis of a single shot which presents an ekphrastic re-configuration of one particular work of European art, Jacques-Louis David’s Portrait of Madame Récamier (1800). The author argues that the use of ekphrasis in the video—through elaboration (close-ups and editing) and repurposing of the source material (painting)—plays an important role in the construction of the theme of “absence”: invoking not only what is represented, but what is not represented in David’s painting. It also foregrounds the potential of ekphrasis as a tool of political and cultural resistance, in the way it intervenes in the representation of the “other” in art and in the museum space.

Shallow landslide occurrence and propagation in tropical mountainous terrain with open source models. A case study in the Colombian Andes.

2021 ◽  
Author(s):  
Johnnatan Palacio ◽  
Edier Aristizábal ◽  
Martin Mergili ◽  
Oscar Echeverri
Keyword(s):  
Open Source ◽  
Limit Equilibrium ◽  
Shallow Landslide ◽  
Climatic Conditions ◽  
Mountainous Terrain ◽  
Model Combination ◽  
Propagation Models ◽  
Landslide Occurrence ◽  
Flow Parameters ◽  
Source Models

<p>Colombia is located in a tropical environment with mostly warm and humid climatic conditions and complex mountainous terrain, where landslides triggered by intense rainfall are very common. Therefore, determining the occurrence and propagation of these events is of great interest in risk management and territorial planning programs.</p><p>Landslide propagation is difficult to predict due to uncertainties of rheological properties as well as initiation and dynamics of rock or sediment mobilization.  In Colombia, methodologies and models for landslide propagation have been less addressed than those corresponding to the occurrence, even though the consequences on people and infrastructure are generally are strongly related to travel distances and impact areas. Most propagation models are based on empirical methods to establish the travel distance of the sliding material, employing geometric approximations or geomorphological interpretation. In the last decades, physically based dynamic landslide propagation models have been proposed. These models use digital elevation models in combination with flow parameters. Their application represents a complex task because of the difficulty in constraining – depending on the model – sometimes the large number of relevant flow parameters.</p><p>In this study, we apply two open source models that work as extensions to the GRASS GIS software: (i) the <em>r.slope.stability</em> model for slope stability assessment using a limit equilibrium model for different sliding surface geometries, together with a probabilistic analysis applied to a range of geotechnical parameters (cohesion, internal friction); and (ii) <em>r.avaflow </em>for landslide propagation, which employs a multi-phase model considering solids and fluids. The models are implemented in the catchment area known as La Arenosa (9.9 km<sup>2</sup>), located in the municipality of San Carlos (Antioquia, Colombia). On September 21, 1990, an event of rainfall of short duration and high intensity precipitated on La Arenosa catchment. approx. 200 mm of precipitation fell within the study area in less than 3 hours, triggering approx. 700 landslides many of which have converted into hillslope debris flows. The zones categorized with a high probability of failure through <em>r.slope.stability</em> are defined as source areas and propagated down with <em>r.avaflow.</em> The results are evaluated against the landslide inventory in order to evaluate the potential of the proposed model combination for predictive simulations.</p>

A general inverse method for modelling extensional sedimentary basins

2000 ◽  
Vol 12 (3-4) ◽  
pp. 219-226 ◽  
Author(s):  
P. Bellingham ◽  
N. White
Keyword(s):  
Inverse Method ◽  
Sedimentary Basins
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