scholarly journals Earthquake dynamics constrained from laboratory experiments: new insights from granular materials

2021 ◽  
Vol 64 (4) ◽  
pp. SE441
Author(s):  
Andrea Bizzarri ◽  
Alberto Petri ◽  
Andrea Baldassarri
Keyword(s):  
Granular Materials ◽  
Laboratory Experiments ◽  
Seismic Waves ◽  
Laboratory Data ◽  
Numerical Approach ◽  
Earthquake Dynamics ◽  
Friction Behavior ◽  
Dynamic Propagation ◽  
State Dependent ◽  
Basic Features

The traction evolution is a fundamental ingredient to model the dynamics of an earthquake rupture which ultimately controls, during the coseismic phase, the energy release, the stress redistribution and the consequent excitation of seismic waves. In the present paper we explore the use of the friction behavior derived from laboratory shear experiments performed on granular materials at low normal stress. We find that the rheological properties emerging from these laboratory experiments can not be described in terms of preexisting governing models already presented in literature; our results indicate that neither rate–and state–dependent friction laws nor nonlinear slip–dependent models, commonly adopted for modeling earthquake ruptures, are able to capture all the features of the experimental data. Then, by exploiting a novel numerical approach, we directly incorporate the laboratory data into a code to simulate the fully dynamic propagation of a 3–D slip failure. We demonstrate that the rheology of the granular material, imposed as fault boundary condition, is dynamically consistent. Indeed, it is able to reproduce the basic features of a crustal earthquake, spontaneously accelerating up to some terminal rupture speed, both sub– and supershear.

scholarly journals On the point-source approximation of earthquake dynamics

2014 ◽  
Vol 57 (3) ◽  
Author(s):  
Andrea Bizzarri
Keyword(s):  
Point Source ◽  
Seismic Waves ◽  
Single Point ◽  
Seismic Source ◽  
Transition Process ◽  
Point Sources ◽  
Multiple Point ◽  
Earthquake Dynamics ◽  
Planar Fault ◽  
Source Models

<p>The focus on the present study is on the point-source approximation of a seismic source. First, we compare the synthetic motions on the free surface resulting from different analytical evolutions of the seismic source (the Gabor signal (G), the Bouchon ramp (B), the Cotton and Campillo ramp (CC), the Yoffe function (Y) and the Liu and Archuleta function (LA)). Our numerical experiments indicate that the CC and the Y functions produce synthetics with larger oscillations and correspondingly they have a higher frequency content. Moreover, the CC and the Y functions tend to produce higher peaks in the ground velocity (roughly of a factor of two). We have also found that the falloff at high frequencies is quite different: it roughly follows ω<span><sup>−2</sup></span> in the case of G and LA functions, it decays more faster than ω<span><sup>−2</sup></span> for the B function, while it is slow than ω<span><sup>−1</sup></span> for both the CC and the Y solutions. Then we perform a comparison of seismic waves resulting from 3-D extended ruptures (both supershear and subshear) obeying to different governing laws against those from a single point-source having the same features. It is shown that the point-source models tend to overestimate the ground motions and that they completely miss the Mach fronts emerging from the supershear transition process. When we compare the extended fault solutions against a multiple point-sources model the agreement becomes more significant, although relevant discrepancies still persist. Our results confirm that, and more importantly quantify how, the point-source approximation is unable to adequately describe the radiation emitted during a real world earthquake, even in the most idealized case of planar fault with homogeneous properties and embedded in a homogeneous, perfectly elastic medium.</p>

Analysis of the World's First Polymer Injectivity Test in a Carbonate Reservoir Under Extreme Harsh Conditions in ADNOC's Reservoirs

2021 ◽  
Author(s):  
Juan Manuel Leon ◽  
Shehadeh K. Masalmeh ◽  
Siqing Xu ◽  
Ali M. AlSumaiti ◽  
Ahmed A. BinAmro ◽  
...  
Keyword(s):  
High Temperature ◽  
Laboratory Experiments ◽  
High Salinity ◽  
Laboratory Data ◽  
Injection Pressure ◽  
Carbonate Reservoir ◽  
Experimental Program ◽  
Full Field ◽  
Harsh Conditions

Abstract Assessing polymer injectivity for EOR field applications is highly important and challenging. An excessive injectivity reduction during and after polymer injection may potentially affect the well integrity and recovery efficiency and consequently, injection strategy and the economics of the polymer projects. Moreover, well conditions such as skin, completion configuration, and injection water quality can significantly impact polymer injectivity. Additionally, the presence of fractures or micro-fractures may govern injection pressure. In contrast, historic field applications have shown that polymer injectivity is in general better than expected from simulations or laboratory data. In the laboratory experiments, the polymer injectivity has been evaluated by injection of significant amounts of pore volumes of polymer at relevant well-injection rates. In addition, several experiments were performed to measure the complex in-situ rheology expected to dominate the flow near the wellbore This paper presents the analysis of the the world's first polymer injectivity test (PIT) conducted in a high temperature and high salinity (HTHS) carbonate reservoir in Abu Dhabi as part of a comprehensive de-risking program for a new polymer-based EOR scheme proposed by ADNOC for these challenging carbonate reservoirs (see Masalmeh et. al., 2014). The de-risking program includes an extensive laboratory experimental program and field injectivity test to ensure that the identified polymer can be injected and propagated in the target formation before multi-well pilot and full-field implementation stages. Experimental laboratory data and the field injectivity test results are presented in earlier publications (Masalmeh et. al., 2019; Rachapudi et. al., 2020) and references therein. This PIT is the world's first polymer injectivity test in a carbonate reservoir under such harsh conditions of high salinity, high content of divalent ions and high temperature. In addition, the polymer used during the test has never been field-tested before. Therefore, the results of the PIT interpretation will help to de-risk the suitable polymer for the future inter-well pilot for the new proposed EOR Polymer-based scheme and it is a game-changer to unlock several opportunities for different Chemical EOR applications on full-field scale in other reservoirs with similar characteristics. A single well radial simulation model was built to integrate the surveillance data during PIT and the extensive laboratory experiments. Morever, multiple Pressure Fall Off Tests (PFOs) during the same periods were analyzed and intergaretd in the model.The study assessed the effect of polymer viscosity on mobility reduction, evaluated the polymer bank propagation, investigated the effect of the skin build-up, residual resistance factor (RRF) and shear effects on the well injectivity. Additionally, a comprehensive assisted history match method and robust simulation sensitivity analysis was implemented, thousands of sensitivity simulation runs were performed to capture several possible injection scenarios and validate laboratory parameters. The simulation study confirmed that the PIT could be interpreted using the laboratory-measured polymer parameters such as polymer bulk viscosity, in-situ rheology, RRF and adsorption.

DEM Simulations in Geotechnical Earthquake Engineering Education

2012 ◽  
pp. 100-109
Author(s):  
J. S. Vinod
Keyword(s):  
Engineering Education ◽  
Granular Materials ◽  
Earthquake Engineering ◽  
Laboratory Experiments ◽  
Computational Models ◽  
Cyclic Behavior ◽  
Advanced Mathematics ◽  
Loading Conditions ◽  
Geotechnical Earthquake Engineering ◽  
Element Method

Behaviour of geotechnical material is very complex. Most of the theoretical frame work to understand the behaviour of geotechnical materials under different loading conditions depends on the strong background of the basic civil engineering subjects and advanced mathematics. However, it is fact that the complete behaviour of geotechnical material cannot be traced within theoretical framework. Recently, computational models based on Finite Element Method (FEM) are used to understand the behaviour of geotechnical problems. FEM models are quite complex and is of little interest to undergraduate students. A simple computational tool developed using Discrete Element Method (DEM) to simulate the laboratory experiments will be cutting edge research for geotechnical earthquake engineering education. This article summarizes the potential of DEM to simulate the cyclic triaxial behaviour of granular materials under complex loading conditions. It is shown that DEM is capable of simulating the cyclic behavior of granular materials (e.g. undrained, liquefaction and post liquefaction) similar to the laboratory experiments.

Effect of Spatial Variation of a Wave Field on the Resulting Ripple Characteristics and Comparison to Present Ripple Predictors

2009 ◽  
Author(s):  
Blake J. Landry ◽  
Yovanni A. Catan˜o-Lopera ◽  
Matthew J. Hancock ◽  
Chiang C. Mei ◽  
Marcelo H. Garci´a
Keyword(s):  
Spatial Variation ◽  
Wave Field ◽  
Test Section ◽  
Laboratory Experiments ◽  
Laboratory Data ◽  
Standing Waves ◽  
Sand Ripple ◽  
Wave Measurements ◽  
Progressive Waves ◽  
Sediment Test

Laboratory experiments analyzed herein focus on the validity of ripple predictors under spatially variable wave envelopes. Present-day ripple predictors commonly derived from laboratory data (for smaller wave periods of about 1 to 4 s) within which only small regions of the facilities were used to observe and measure the sand ripple geometric characteristics of the nearly progressive waves measured overhead. When extended to large sediment test sections, our results show that the predictors are still valid along the tank under wave conditions which have significant wave envelope spatial variation (e.g., standing waves), provided that ripple predictors use the wave measurements directly above the respective locations within the computations. Results indicate that even under the case of mild reflection, noticeable variation in ripple characteristics can be seen along the sediment test section; thus, compels the necessity of measuring the wave field along the entire sediment section to achieve accurate results.

scholarly journals Seismic surveying and imaging at the laboratory scale: A framework to cross-validate experiments and simulations for a salt-body environment

Geophysics ◽  
2020 ◽  
Vol 85 (3) ◽  
pp. T123-T139
Author(s):  
Bence Solymosi ◽  
Nathalie Favretto-Cristini ◽  
Vadim Monteiller ◽  
Paul Cristini ◽  
Bjørn Ursin ◽  
...  
Keyword(s):  
Experimental Data ◽  
Laboratory Experiments ◽  
Field Experiments ◽  
Imaging Techniques ◽  
Laboratory Data ◽  
Seismic Exploration ◽  
Scale Model ◽  
Water Tank ◽  
Time Migration ◽  
Reduced Scale

Laboratory experiments have been recently reintroduced into the ideas-to-applications pipeline for geophysical applications. Benefiting from recent technological advances, we believe that in the coming years, laboratory experiments can play a major role in supporting field experiments and numerical modeling, to explore some of the current challenges of seismic imaging in terms of, for instance, acquisition design or benchmarking of new imaging techniques at a low cost and in an agile way. But having confidence in the quality and accuracy of the experimental data obtained in a complex configuration, which mimics at a reduced scale a real geologic environment, is an essential prerequisite. This requires a robust framework regardless of the configuration studied. Our goal is to provide a global overview of this framework in the context of offshore seismics. To illustrate it, a reduced-scale model is used to represent a 3D complex-shaped salt body buried in sedimentary layers with curved surfaces. Zero-offset and offset reflection data are collected in a water tank, using a conventional pulse-echo technique. Then, a cross-validation approach is applied, which allows us, through comparison between experimental data and the numerical simulation, to point out some necessary future improvements of the laboratory setup to increase the accuracy of the experimental data, and the limitations of the numerical implementation that must also be tackled. Due to this approach, a hierarchical list of points can be collected, to which particular attention should be paid to make laboratory experiments an efficient tool in seismic exploration. Finally, the quality of the complex reduced-scale model and the global framework is successfully validated by applying reverse time migration to the laboratory data.

An experimental study of the surface elevation probability distribution and statistics of wind-generated waves

1980 ◽  
Vol 101 (1) ◽  
pp. 179-200 ◽  
Author(s):  
Norden E. Huang ◽  
Steven R. Long
Keyword(s):  
Experimental Study ◽  
Probability Density Function ◽  
Probability Distribution ◽  
Wave Field ◽  
Field Data ◽  
Laboratory Experiments ◽  
Laboratory Data ◽  
Surface Elevation ◽  
Strong Wind ◽  
Non Gaussian

Laboratory experiments were conducted to measure the surface elevation probability density function and associated statistical properties for a wind-generated wave field. The laboratory data together with some limited field data were compared. It is found that the skewness of the surface elevation distribution is proportional to the significant slope of the wave field, §, and all the laboratory and field data are best fitted by \[ K_3 = 8\pi\S, \] with § defined as ($(\overline{\zeta^2})^{\frac{1}{2}}/\lambda_0 $, where ζ is the surface elevation, and λ0 is the wavelength of the energy-containing waves. The value of K3 under strong wind could reach unity. Even under these highly non-Gaussian conditions, the distribution can be approximated by a four-term Gram-Charlier expansion. The approximation does not converge uniformly, however. More terms will make the approximation worse.

Influence of Host Nitrogen Levels on Development, Survival, Size and Population-Dynamics of Sugarcane Mealybug, Saccharicoccus-Sacchari (Cockerell) (Hemiptera, Pseudococcidae)

1992 ◽  
Vol 40 (3) ◽  
pp. 327 ◽  
Author(s):  
DJ Rae ◽  
RE Jones
Keyword(s):  
Population Dynamics ◽  
Laboratory Experiments ◽  
Laboratory Data ◽  
Growing Season ◽  
Seasonal Effects ◽  
Detectable Effect ◽  
Soluble Nitrogen ◽  
Nitrogen Levels ◽  
Nitrogen Concentrations ◽  
Saccharicoccus Sacchari

Nitrogen levels in commercial plots of sugarcane varied over the cane-growing season. However, when adjusted for seasonal effects, nitrogen did not have a detectable effect on the size of mealybug populations on cane. In laboratory experiments, the survival of immature Saccharicoccus sacchari and the size attained at the onset of the oviposition period was influenced by the level of nitrogen fertiliser applied to potted sugarcane. Survival of S. sacchari increased to a maximum at 320 mg L-1 soluble nitrogen in sugarcane and decreased at higher levels, while size increased with increased nitrogen over the whole range of concentrations tested. Nitrogen-driven changes in the abundance of S. sacchari predicted from laboratory data indicate that normal variations in nitrogen concentrations of field-grown sugarcane have little effect on the population dynamics of S. sacchari.

THE REPRODUCTIVE CYCLES OF MALE AND FEMALE LYTTA NUTTALLI (COLEOPTERA: MELOIDAE)

1976 ◽  
Vol 108 (10) ◽  
pp. 1125-1136 ◽  
Author(s):  
G. H. Gerber ◽  
N. S. Church
Keyword(s):  
Oocyte Maturation ◽  
Laboratory Experiments ◽  
Male And Female ◽  
The One ◽  
Basic Features ◽  
Reproductive Cycles

AbstractLaboratory experiments showed that female Lytta nuttalli Say are capable of developing and depositing more than one batch of eggs. The largest number of batches deposited by a female was 5. Batches laid by one female are the same size, and each batch represents one gonadotropic cycle. Most females lay every 4 to 8 days, the most frequent intervals between consecutive ovipositions being 5 and 6 days. The females copulate at least once before the first oviposition and usually again within 24 h after each oviposition. The first copulation stimulates oocyte maturation and probably also deposition of the first batch of eggs. Additional copulations are not needed for the development and deposition of subsequent egg batches, but appear to stimulate egg output. Sufficient spermatozoa are transferred to the female during the one or more copulations preceding the first oviposition to fertilize all the eggs she produces. The largest number of copulations by a male was 9. Males can copulate as frequently as every 24 h, but the most frequent intervals between copulations in virile males are 2 and 3 days. The basic features of the reproductive cycles of male and female L. nuttalli are found in other Meloinae and probably are characteristic of the subfamily. The fairly large quantities of spermatophoral materials from repeated copulations may be important in the nutrition of the female.

scholarly journals Liquefaction

2021 ◽  
pp. 301-321
Author(s):  
Chi-Yuen Wang ◽  
Michael Manga
Keyword(s):  
Experimental Data ◽  
Energy Density ◽  
Seismic Waves ◽  
Near Field ◽  
Laboratory Data ◽  
Seismic Energy ◽  
Silty Sand ◽  
Engineered Structures ◽  
Outstanding Question ◽  
Extensive Experimental Data

AbstractLiquefaction of the ground during earthquakes has long been documented and has drawn much attention from earthquake engineers because of its devastation to engineered structures. In this chapter we review a few of the best studied field cases and summarize insights from extensive experimental data critical for understanding the interaction between earthquakes and liquefaction. Despite the progress made in the last few decades, several outstanding problems remain unanswered. One is the mechanism for liquefaction beyond the near field, which has been abundantly documented in the field. This is not well understood because, according to laboratory data, liquefaction should occur only in the near field where the seismic energy density is great enough to cause undrained consolidation leading up to liquefaction. Another outstanding question is the dependence of liquefaction on the frequency of the seismic waves, where the current results from the field and laboratory studies are in conflict. Finally, while in most cases the liquefied sediments are sand or silty sand, well-graded gravel has increasingly been witnessed to liquefy during earthquakes and is not simply the result of entrainment by liquified sand. It is challenging to explain how pore pressure could build up in gravely soils and be maintained at a level high enough to cause liquefaction.

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