The relevance of rock shape over mass—implications for rockfall hazard assessments

AbstractThe mitigation of rapid mass movements involves a subtle interplay between field surveys, numerical modelling, and experience. Hazard engineers rely on a combination of best practices and, if available, historical facts as a vital prerequisite in establishing reproducible and accurate hazard zoning. Full-scale field tests have been performed to reinforce the physical understanding of debris flows and snow avalanches. Rockfall dynamics are - especially the quantification of energy dissipation during the complex rock-ground interaction - largely unknown. The awareness of rock shape dependence is growing, but presently, there exists little experimental basis on how rockfall hazard scales with rock mass, size, and shape. Here, we present a unique data set of induced single-block rockfall events comprising data from equant and wheel-shaped blocks with masses up to 2670 kg, quantifying the influence of rock shape and mass on lateral spreading and longitudinal runout and hence challenging common practices in rockfall hazard assessment.

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Imaging ground surface deformations in post-disaster settings via small UAVs

Geoscience Letters ◽

10.1186/s40562-021-00194-8 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Richard L. Ybañez ◽

Audrei Anne B. Ybañez ◽

Alfredo Mahar Francisco A. Lagmay ◽

Mario A. Aurelio

Keyword(s):

Surface Deformation ◽

Ground Surface ◽

Point Clouds ◽

Lateral Spreading ◽

Fault Movement ◽

Field Surveys ◽

3D Point Clouds ◽

Vertical Displacements ◽

Resolution Imaging ◽

Post Disaster

AbstractSmall unmanned aerial vehicles have been seeing increased deployment in field surveys in recent years. Their portability, maneuverability, and high-resolution imaging are useful in mapping surface features that satellite- and plane-mounted imaging systems could not access. In this study, we develop and apply a workplan for implementing UAV surveys in post-disaster settings to optimize the flights for the needs of the scientific team and first responders. Three disasters caused by geophysical hazards and their associated surface deformation impacts were studied implementing this workplan and was optimized based on the target features and environmental conditions. An earthquake that caused lateral spreading and damaged houses and roads near riverine areas were observed in drone images to have lengths of up to 40 m and vertical displacements of 60 cm. Drone surveys captured 2D aerial raster images and 3D point clouds leading to the preservation of these features in soft-sedimentary ground which were found to be tilled over after only 3 months. The point cloud provided a stored 3D environment where further analysis of the mechanisms leading to these fissures is possible. In another earthquake-devastated locale, areas hypothesized to contain the suspected source fault zone necessitated low-altitude UAV imaging below the treeline capturing Riedel shears with centimetric accuracy that supported the existence of extensional surface deformation due to fault movement. In the aftermath of a phreatomagmatic eruption and the formation of sub-metric fissures in nearby towns, high-altitude flights allowed for the identification of the location and dominant NE–SW trend of these fissures suggesting horst-and-graben structures. The workplan implemented and refined during these deployments will prove useful in surveying other post-disaster settings around the world, optimizing data collection while minimizing risk to the drone and the drone operators.

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Three-Dimensional Structures in Experimental Density Currents

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2007-37571 ◽

2007 ◽

Author(s):

B. Firoozabadi ◽

H. Afshin ◽

E. Safaaee

Keyword(s):

Salt Solution ◽

Chemical Elements ◽

Three Dimensional ◽

Lateral Spreading ◽

Current Data ◽

Density Current ◽

Density Currents ◽

Ambient Water ◽

Data Set ◽

Bed Slope

Density currents are continuous currents which move down-slope due to the fact that their density is greater than that of ambient water. The density difference is caused by temperature differences, chemical elements, dissolved materials, or suspended sediment. Many researchers have studied the density current structures, their complexities and uncertainties. However, there is not a detailed 3-D turbulent density current data set perfectly. In this work, the structure of 3-dimensional salt solution density currents is investigated. A laboratory channel was used to study the flow resulting from the release of salt solution into freshwater over an inclined bed. The experiments were conducted with different bottom slopes, inlet concentrations and flow rates. In these tests, the instantaneous velocities are measured by an ADV apparatus (Acoustic Doppler Velocimeter). Results show that by increasing the bed-slope and inlet concentrations, the height of the current decreases. As the density current moves downward the channel or by increasing the discharge, the height of the density current increases. Finally, the effects of different variables such as the bed slope, concentration and flow rate of entering fluid on the velocity profile in different distances from the entrance is studied. The entrainment coefficient, lateral spreading and drag coefficient of the bed and shear layer between salt solution and ambient water is discussed.

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YSTAR: Yonsei Survey Telescopes for Astronomical Research

International Astronomical Union Colloquium ◽

10.1017/s0252921100078659 ◽

2001 ◽

Vol 183 ◽

pp. 83-87

Author(s):

Yong-Ik Byun ◽

Won-Yong Han ◽

Yong-Woo Kang ◽

Moo-Young Chun ◽

Sung-Yeol Yu ◽

...

Keyword(s):

South Africa ◽

Variable Stars ◽

Primary Objective ◽

Wide Field ◽

Target Acquisition ◽

Data Set ◽

Field Surveys ◽

Sky Survey ◽

Two Factors ◽

Astronomical Research

AbstractThe YSTAR program is a general sky survey looking for variability. The main equipments are three 0.5-m telescopes. These telescopes have fast F/2 optics covering nearly 3.5 square degree field onto a 2K CCD. They also have very fast slew capability, which exceeds 10 degrees per second. These two factors make them most suitable for rapid target acquisition and wide-field surveys of various kinds. Our primary objective is to identify and monitor variable stars down to 18th R-magnitude, and our observing mode allows the same data set to be also useful in identifying asteroids. Our first telescope has just begun regular automated operation, and the second telescope will be installed in South Africa within this year to provide coverage of the southern sky.

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Investigation of ULF magnetic pulsations, air conductivity changes, and infra red signatures associated with the 30 October Alum Rock M5.4 earthquake

Natural Hazards and Earth System Science ◽

10.5194/nhess-9-585-2009 ◽

2009 ◽

Vol 9 (2) ◽

pp. 585-603 ◽

Cited By ~ 36

Author(s):

T. Bleier ◽

C. Dunson ◽

M. Maniscalco ◽

N. Bryant ◽

R. Bambery ◽

...

Keyword(s):

Field Data ◽

Low Frequency ◽

Field Tests ◽

P Wave ◽

Electromagnetic Signal ◽

San Jose ◽

Data Set ◽

Bay Area ◽

Conductivity Sensor ◽

Magnetic Pulsations

Abstract. Several electromagnetic signal types were observed prior to and immediately after 30 October 2007 (Local Time) M5.4 earthquake at Alum Rock, Ca with an epicenter ~15 km NE of San Jose Ca. The area where this event occurred had been monitored since November 2005 by a QuakeFinder magnetometer site, unit 609, 2 km from the epicenter. This instrument is one of 53 stations of the QuakeFinder (QF) California Magnetometer Network-CalMagNet. This station included an ultra low frequency (ULF) 3-axis induction magnetometer, a simple air conductivity sensor to measure relative airborne ion concentrations, and a geophone to identify the arrival of the P-wave from an earthquake. Similar in frequency content to the increased ULF activity reported two weeks prior to the Loma Prieta M7.0 quake in 1989 (Fraser-Smith, 1990, 1991), the QF station detected activity in the 0.01–12 Hz bands, but it consisted of an increasing number of short duration (1 to 30 s duration) pulsations. The pulsations peaked around 13 days prior to the event. The amplitudes of the pulses were strong, (3–20 nT), compared to the average ambient noise at the site, (10–250 pT), which included a component arising from the Bay Area Rapid Transit (BART) operations. The QF station also detected different pulse shapes, e.g. negative or positive only polarity, with some pulses including a combination of positive and negative. Typical pulse counts over the previous year ranged from 0–15 per day, while the count rose to 176 (east-west channel) on 17 October, 13 days prior to the quake. The air conductivity sensor saturated for over 14 h during the night and morning prior to the quake, which occurred at 20:29 LT. Anomalous IR signatures were also observed in the general area, within 50 km of the epicenter, during the 2 weeks prior to the quake. These three simultaneous EM phenomena were compared with data collected over a 1–2-year period at the site. The data was also compared against accounts of air ionization reported to be associated with radon emission from the ground (Ouzounov, 2007), and a series of laboratory rock stressing experiments (Freund, 2006, 2007a, b, c) to determine if field data was consistent either of these accounts. We could not find a data set with pre-earthquake radon measurements taken near the Alum Rock epicenter to compare against our field data. However, based on the Alum Rock data set example and another data set at Parkfield, the field tests are at least consistent with the lab experiments showing currents, magnetic field disturbances, air conductivity changes, and IR signatures. This is encouraging, but more instrumented earthquake examples are needed to prove a repeating pattern for these types of pre-earthquake EM signatures. For more information on QuakeFinder please view http://www.quakefinder.com.

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DISPERSANT EFFECTIVENESS IN FIELD TRIALS AND IN OPERATIONAL RESPONSE

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-1997-1-923 ◽

1997 ◽

Vol 1997 (1) ◽

pp. 923-923

Author(s):

Tim Lunel ◽

Peter Wood ◽

Louise Davies

Keyword(s):

North Sea ◽

Quantitative Data ◽

Field Tests ◽

Field Trials ◽

Data Set ◽

Oil Droplet ◽

The North ◽

The North Sea ◽

Dispersant Effectiveness ◽

Oil Droplet Size

ABSTRACT The North Sea field tests described in the paper have provided a quantitative data set on dispersant efficiency that can be used to calibrate laboratory dispersant tests. Comparisons of efficiency figures from the EXDET, IFP, Swirling Flask, and WSL tests with the field dispersant efficiency figures indicate that the WSL test comes closest to replicating the observed dispersion, in terms of both the percentage of oil dispersed and the oil droplet size of the dispersion. This paper, with the accompanying presentation in the Sea Empress session of the conference, demonstrates that a combination of quantitative field tests and the WSL test can be used to guide responders in decisions of whether to use dispersants in response to an oil spill. The WSL test and the field trials indicated that dispersants were likely to be effective against both the Forties Blend crude oil and the weathered oil. These predictions were confirmed by the successful dispersant operation at the Sea Empress incident.

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Danish earthquake recorded by distributed acoustic sensing (DAS)

10.5194/egusphere-egu2020-8442 ◽

2020 ◽

Author(s):

Camilla Rasmussen ◽

Peter H. Voss ◽

Trine Dahl-Jensen

Keyword(s):

Field Test ◽

Signal To Noise Ratio ◽

Field Tests ◽

Small Subset ◽

Fibre Optic ◽

Data Set ◽

Acoustic Sensing ◽

Arrival Times ◽

Fibre Optic Cable ◽

Distributed Acoustic Sensing

On September 16th 2018 a Danish earthquake of local magnitude 3.7 was recorded by distributed acoustic sensing (DAS) in a ~23 km long fibre-optic cable. The data are used to study how well DAS can be used as a supplement to conventional seismological data in earthquake localisation. One of the goals in this study is extracting a small subset of traces with clear P and S phases to use in an earthquake localisation, from the 11144 traces the DAS system provide. The timing in the DAS data might not be reliable, and therefore differences in arrival times of S and P are used instead of the exact arrival times. The DAS data set is generally noisy and with a low signal-to-noise ratio (SNR). It is examined whether stacking can be used to improve SNR. The SNR varies a lot along the fibre-optic cable, and at some distances, it is so small that the traces are useless. Stacking methods for improving SNR are presented.A field test at two location sites of the fibre-optic cable was conducted with the purpose of comparing DAS data with seismometer data. At the field sites, hammer shots were recorded by a small array of three STS-2 sensors located in a line parallel to the fibre-optic cable. The recordings generally show good consistency between the two data sets.&#160; In addition, the field tests are used to get a better understanding of the noise sources in the DAS recording of the earthquake. There are many sources of noise in the data set. The most prominent are a line of windmills that cross the fibre-optic cable and people walking in the building where the detector is located. Also, the coupling between the fibre-optic cable and the ground varies along the cable length due to varying soil type and wrapping around the fibre-optic cable, which is also evident in field test data. Furthermore, the data from the field tests are used to calibrate the location of the fibre-optic cable, which is necessary for using the DAS data in an earthquake localisation. Data processing is done in Matlab and SEISAN.

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DAMAGE TO REINFORCED CONCRETE BUILDINGS AND COASTAL TREES DUE TO THE 2011 OFF THE PACIFIC COAST OF TOHOKU EARTHQUAKE TSUNAMI

Coastal Engineering Proceedings ◽

10.9753/icce.v33.management.51 ◽

2012 ◽

Vol 1 (33) ◽

pp. 51 ◽

Cited By ~ 4

Author(s):

Hideo Matsutomi ◽

Eriko Yamaguchi ◽

Kazunori Naoe ◽

Kenji Harada

Keyword(s):

Pacific Coast ◽

Vertical Section ◽

Flow Direction ◽

Vertical Wall ◽

Field Tests ◽

Tohoku Earthquake ◽

Simple Method ◽

Field Surveys ◽

The Pacific ◽

Damage Condition

Macroscopic conditions of the damage to RC building and coastal black pine tree in the 2011 Off the Pacific Coast of Tohoku Earthquake Tsunami are discussed through field surveys and field tests. Effects of RC building’s location and arrangement, submerged vertical section area in the tsunami inundation flow direction, ratio of the area of submerged windows and/or doorways to the area of submerged vertical wall on the side hit by the inundation flow (so-called, aperture ratio), and foundation piles on the damage condition of the building are examined. The damage condition of the coastal tree is also discussed from the viewpoints of the drag force and moment assessed using inundation flow velocity estimated by a simple method. Moreover, effects and limits of coastal woods on the tsunami energy and force reductions are illustrated through the field surveys.

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PALWEED: WHEAT II: revision of a weed management decision model in response to field testing

Weed Science ◽

10.1017/s0043174500090433 ◽

1998 ◽

Vol 46 (2) ◽

pp. 205-213 ◽

Cited By ~ 6

Author(s):

Tae-Jin Kwon ◽

Douglas L. Young ◽

Frank L. Young ◽

Chris M. Boerboom

Keyword(s):

Winter Wheat ◽

Weed Management ◽

Decision Model ◽

Wheat Yield ◽

Field Tests ◽

Field Testing ◽

Original Model ◽

Linear Functions ◽

Management Decision ◽

Data Set

PALWEED:WHEAT is a bioeconomic decision model for determining profit-maximizing postemergence herbicide treatments for winter wheat in the Washington–Idaho Palouse region. PALWEED:WHEAT performed relatively well economically in 2 yr of on-farm field tests. However, the model was less sensitive than desired in prescribing postemergence broadleaved herbicides in the presence of high densities of broadleaved weed seedlings. Therefore, PALWEED:WHEAT was revised in response to the field testing. This paper compares the revised model's agronomic and economic performance to the original model in computer simulations. The revised model, PALWEED:WHEAT II, differs from the original model in several respects: (1) exponential functions replace linear functions in predicting weed survival, (2) preplant application of a nonselective herbicide is entered as an exogenous binary variable, (3) separate indices of broadleaved and grass competition are substituted for an aggregate weed competition index in the wheat yield function, (4) hyperbolic replaces logistic functional representation of weed damage to wheat yield, and (5) separate models are estimated for winter wheat after spring dry pea and for winter wheat in all examined crop rotation positions. In simulations including a variety of agronomic and economic conditions, PALWEED:WHEAT II recommended postemergence herbicide types and rates that consistently complied with agronomic and economic theory. Furthermore, the revised model, especially when estimated from the relevant wheat after pea data set, was markedly more balanced in recommending both broadleaved and grass herbicides in response to observed densities of both weed groups. The substantial change in herbicide recommendations in response to changes in model functional specifications following field testing confirms the importance of field testing and revision of bioeconomic decision models.

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Bayesian stochastic modeling of a spherical rock bouncing on a coarse soil

Natural Hazards and Earth System Science ◽

10.5194/nhess-9-831-2009 ◽

2009 ◽

Vol 9 (3) ◽

pp. 831-846 ◽

Cited By ~ 20

Author(s):

F. Bourrier ◽

N. Eckert ◽

F. Nicot ◽

F. Darve

Keyword(s):

Numerical Data ◽

Taylor Series Expansion ◽

Hazard Mapping ◽

Special Focus ◽

Data Set ◽

Rockfall Hazard ◽

Local Soil ◽

Analysis Models ◽

The Impact ◽

Coarse Soil

Abstract. Trajectory analysis models are increasingly used for rockfall hazard mapping. However, classical approaches only partially account for the variability of the trajectories. In this paper, a general formulation using a Taylor series expansion is proposed for the quantification of the relative importance of the different processes that explain the variability of the reflected velocity vector after bouncing. A stochastic bouncing model is obtained using a statistical analysis of a large numerical data set. Estimation is performed using hierarchical Bayesian modeling schemes. The model introduces information on the coupling of the reflected and incident velocity vectors, which satisfactorily expresses the mechanisms associated with boulder bouncing. The approach proposed is detailed in the case of the impact of a spherical boulder on a coarse soil, with special focus on the influence of soil particles' geometrical configuration near the impact point and kinematic parameters of the rock before bouncing. The results show that a first-order expansion is sufficient for the case studied and emphasize the predominant role of the local soil properties on the reflected velocity vector's variability. The proposed model is compared with classical approaches and the interest for rockfall hazard assessment of reliable stochastic bouncing models in trajectory simulations is illustrated with a simple case study.

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Probabilistic Calculations of Groundwater Travel Time in Heterogeneous Three-Dimensional Porous Media

MRS Proceedings ◽

10.1557/proc-333-849 ◽

1993 ◽

Vol 333 ◽

Author(s):

Amvrossios C. Bagtzoglou ◽

Robert G. Baca

Keyword(s):

Travel Time ◽

Nearest Neighbor ◽

Three Dimensional ◽

Stochastic Theory ◽

Field Tests ◽

Yucca Mountain ◽

High Level Waste ◽

Large Space ◽

Data Set ◽

Specific Flow

ABSTRACTGroundwater travel time (GWTT) estimation at a potential high-level waste (HLW) repository is subject to various technical uncertainties. These uncertainties stem from model and data uncertainties and cannot be resolved with field tests because of the long time (> 1,000 yr) and large space (> 5,000 m) scales involved. Therefore, computational methods for demonstrating and determining compliance with the GWTT rule will be used. Stochastic theory based approaches constitute a natural framework for performing GWTT estimations under conditions of uncertain and/or limited data.This study employs the generation of spatially correlated hydraulic conductivity fields by the Nearest Neighbor Model (NNM). Repeated (Monte Carlo) realizations of the statistically equivalent random fields are obtained, and the saturated steady-state groundwater flow equation is solved. These results are then used to estimate GWTT along particular paths by releasing a large number of water particles at various starting points. By doing so, path variability is sampled through the realization ensemble space and also through the independent particle “flights” within a specific flow field realization. The uncertainty in predicted GWTT due to parameter variability is assessed for a data set characteristic of the saturated zone at Yucca Mountain at three levels of parameter heterogeneity. However, since several parameters and the boundary conditions of the problem have been arbitrarily assumed, direct conclusions regarding the proposed Yucca Mountain site cannot be drawn from this study.

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