scholarly journals GEODYNAMICS

GEODYNAMICS ◽  
2011 ◽  
Vol 2(11)2011 (2(11)) ◽  
pp. 66-68
Author(s):  
А. R. Gnyp ◽  
Keyword(s):  
Vertical Plane ◽  
Source Mechanism ◽  
Local Source ◽  
Horizontal Gradient ◽  
Single Source ◽  
Normal Faulting ◽  
Vertical Movements ◽  
Source Mechanisms

Three groups of recurrent earthquakes have been identified within the Mukacheve series of 2005–2006. After relocation with application of differential arrivals and station terms their sources arranged into almost a vertical plane along the azimuth of ~120°, approximately coinciding with a plane of normal faulting determined for all the earthquakes as a single source mechanism. The results are consistent with data on some other local source mechanisms as also on an ambient field of extensional stresses in the local crust and a significant horizontal gradient of vertical movements across the epicenter area of the series.

Normal faulting activated by hydraulic fracturing: A case study from the Barnett Shale, Fort Worth Basin

2020 ◽  
Vol 39 (3) ◽  
pp. 204-211
Author(s):  
Dmitry Alexandrov ◽  
Leo Eisner ◽  
Umair bin Waheed ◽  
SanLinn Isma'il Ebrahim Kaka ◽  
Stewart Alan Greenhalgh
Keyword(s):  
Hydraulic Fracturing ◽  
Horizontal Resolution ◽  
Source Mechanism ◽  
Barnett Shale ◽  
Hydraulic Fractures ◽  
Normal Faulting ◽  
Fort Worth Basin ◽  
Economic Methods ◽  
Source Mechanisms

Surface microseismic arrays enable long-term field-scale monitoring over multiple stimulations during the life of an unconventional field. In this study, we show highly economic methods of monitoring with sparse surface arrays in the Barnett Shale and develop an alternatative method of processing to enable good vertical and horizontal resolution of located events. We show that sparse surface monitoring arrays enable not only the detection and location of high numbers of microseismic events but also source mechanism characterization. This case study illustrates how hydraulic fracturing activated normal faulting at a distance of approximately 1 mile from stimulated wells. We show that the source mechanism enables us to resolve between newly created hydraulic fractures and activated faults. The differences in source mechanisms and b-values of newly created fractures and activated faults are consistent with independently processed temporary star-like arrays, which are also deployed over the same stimulation.

Detection, location, and source mechanism determination with large noise variations in surface microseismic monitoring

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. KS197-KS206
Author(s):  
Dmitry Alexandrov ◽  
Leo Eisner ◽  
Umair bin Waheed ◽  
SanLinn I. Kaka ◽  
Stewart Alan Greenhalgh
Keyword(s):  
Noise Level ◽  
Weighted Least Squares ◽  
Computational Cost ◽  
Real Life ◽  
Selection Criterion ◽  
Signal Amplitude ◽  
Threshold Level ◽  
Microseismic Monitoring ◽  
Source Mechanism ◽  
Source Mechanisms

Microseismic monitoring aims at detecting as weak events as possible and providing reliable locations and source mechanisms for these events. Surface monitoring arrays suffer from significant variations of noise levels across receiver lines. When using a large monitoring array, we use a stacking technique to detect microseismic events through maximizing the signal-to-noise ratio (S/N) of the stack. But some receivers with a high noise level do not contribute to improving the S/N of the stack. We have derived a theoretical concept for the proper selection of receivers that best contribute to the stack for a constant strength of a signal across the array. This receiver selection criterion, based on the assumption of constant signal amplitude, provides a robust estimate of the noise threshold level, which could be used to discard or suppress contribution from the receivers that do not improve the S/N of the stack. We found that limiting the number of receivers for stacking improves the location accuracy and reduces the computational cost of data processing. Although the assumption of a constant signal never holds in real-life seismic applications, the noise level varies across the surface receivers in a significantly wider range than the signal amplitude. These noise variations can also increase the uncertainty of the source mechanism inversion and should be accounted for. Synthetic and field data examples show that weighted least-squares inversion with receiver weighting according to the noise level produces more accurate estimates for source mechanisms compared to the inversion that ignores information about noise.

scholarly journals Multi-Joint Coordination of Vertical Arm Movement

2003 ◽  
Vol 1 (1) ◽  
pp. 45-56 ◽  
Author(s):  
Ajay Seth ◽  
John J. McPhee ◽  
Marcus G. Pandy
Keyword(s):  
Sagittal Plane ◽  
Model Simulation ◽  
Vertical Plane ◽  
Arm Movement ◽  
Elbow Flexion ◽  
Vertical Acceleration ◽  
Joint Movement ◽  
Vertical Movements ◽  
Joint Coordination ◽  
Muscle Torques

A model of the human arm was developed to study coordination of multi-joint movement in the vertical plane. The arm was represented as a two-segment, two-degree of freedom dynamic system with net muscle torques acting at the shoulder and elbow. Kinematic data were collected from a subject who performed unrestrained vertical movements with only the initial and final hand elevations prescribed. Movements were performed with and without a hand-held load. The method of computed torques was implemented to obtain net muscle torques, which enables position and velocity feedback to be used to estimate joint angular accelerations that produce a more stable simulation of arm movement. The model simulation was then used to calculate the contributions of the net muscle torques, gravitational torques and velocity-interaction torques to the angular accelerations of the shoulder and elbow and also to the vertical acceleration of the hand. The net muscle torques and gravity were the prime movers of the arm. The velocity-dependent effects contributed little to the dynamics of arm movement and were, in fact, insignificant when the hand was loaded. The muscles of the shoulder and elbow acted synergistically to elevate the arm in the sagittal plane. The hand was accelerated upward by the elbow first, until the point of maximum elbow flexion, after which the shoulder became the prime mover. Gravity acted consistently to accelerate the hand downward. Coordination was notably invariant to changes in external load. Some compensation for load was observed in the control, and these differences were attributed mainly to an increase in system inertia.

scholarly journals Sensitivity of InSAR and teleseismic observations to earthquake rupture segmentation

2020 ◽  
Vol 223 (2) ◽  
pp. 875-907 ◽  
Author(s):  
Andreas Steinberg ◽  
Henriette Sudhaus ◽  
Sebastian Heimann ◽  
Frank Krüger
Keyword(s):  
Robust Estimation ◽  
Field Data ◽  
Near Field ◽  
Point Sources ◽  
Data Sets ◽  
Systematic Bias ◽  
Far Field ◽  
Single Source ◽  
Significant Difference ◽  
Source Mechanisms

SUMMARY Earthquakes often rupture across more than one fault segment. If such rupture segmentation occurs on a significant scale, a simple point-source or one-fault model may not represent the rupture process well. As a consequence earthquake characteristics inferred, based on one-source assumptions, may become systematically wrong. This might have effects on follow-up analyses, for example regional stress field inversions and seismic hazard assessments. While rupture segmentation is evident for most Mw > 7 earthquakes, also smaller ones with 5.5 < Mw < 7 can be segmented. We investigate the sensitivity of globally available data sets to rupture segmentation and their resolution to reliably estimate the mechanisms in presence of segmentation. We focus on the sensitivity of InSAR (Interferometric Synthetic Aperture Radar) data in the static near-field and seismic waveforms in the far-field of the rupture and carry out non-linear and Bayesian optimizations of single-source and two-sources kinematic models (double-couple point sources and finite, rectangular sources) using InSAR and teleseismic waveforms separately. Our case studies comprises of four Mw 6–7 earthquakes: the 2009 L’Aquila and 2016 Amatrice (Italy) and the 2005 and 2008 Zhongba (Tibet) earthquakes. We contrast the data misfits of different source complexity by using the Akaike informational criterion (AIC). We find that the AIC method is well suited for data-driven inferences on significant rupture segmentation for the given data sets. This is based on our observation that an AIC-stated significant improvement of data fit for two-segment models over one-segment models correlates with significantly different mechanisms of the two source segments and their average compared to the single-segment mechanism. We attribute these modelled differences to a sufficient sensitivity of the data to resolve rupture segmentation. Our results show that near-field data are generally more sensitive to rupture segmentation of shallow earthquakes than far-field data but that also teleseismic data can resolve rupture segmentation in the studied magnitude range. We further conclude that a significant difference in the modelled source mechanisms for different segmentations shows that an appropriate choice of model segmentation matters for a robust estimation of source mechanisms. It reduces systematic biases and trade-off and thereby improves the knowledge on the rupture. Our study presents a strategy and method to detect significant rupture segmentation such that an appropriate model complexity can be used in the source mechanism inference. A similar, systematic investigation of earthquakes in the range of Mw 5.5–7 could provide important hazard-relevant statistics on rupture segmentation. In these cases single-source models introduce a systematic bias. Consideration of rupture segmentation therefore matters for a robust estimation of source mechanisms of the studied earthquakes.

scholarly journals Felt index, source parameters and ground motion evaluation for earthquakes at Mt. Vesuvius

2013 ◽  
Vol 56 (4) ◽  
Author(s):  
Elena Cubellis ◽  
Aldo Marturano
Keyword(s):  
Ground Motion ◽  
Source Parameters ◽  
Source Mechanism ◽  
Macroseismic Field ◽  
Continuous Parameter ◽  
Source Mechanisms ◽  
Parameter Values

<p>Results of non-instrumental surveys carried out on recent and past seismicity at Vesuvius have been retaken in order to propose new analyses regarding source mechanisms and causative faults. We present the results of the October 9, 1999, earthquake, the most intense event since the 1944 eruption. The intensity was evaluated by utilizing integer values of the MCS Scale and the felt index as a continuous parameter. Values of magnitude and attenuation determinated by applying macroseismic models to data, and compared to instrumental ones, were utilized to assess the “size” of the historical Vesuvian earthquakes. A magnitude of M = 5.1±.3 was considered for the A.D. 62 earthquake, the largest one of the area that preceded the A.D. 79 famous eruption. By using the macroseismic field of October 9, 1999, the source mechanism of the earthquake was obtained, and synthetic isoseisms and causative fault of the A.D. 62 are also proposed.</p>

scholarly journals Energy-related optimal control accounts for gravitational load: comparing shoulder, elbow, and wrist rotations

2014 ◽  
Vol 111 (1) ◽  
pp. 4-16 ◽  
Author(s):  
Jérémie Gaveau ◽  
Bastien Berret ◽  
Laurent Demougeot ◽  
Luciano Fadiga ◽  
Thierry Pozzo ◽  
...  
Keyword(s):  
Optimal Control ◽  
Planning Process ◽  
Vertical Plane ◽  
Motor Planning ◽  
Gravity Force ◽  
General Idea ◽  
Directional Asymmetry ◽  
Vertical Movements ◽  
Plane Joint ◽  
Experimental Findings

We permanently deal with gravity force. Experimental evidences revealed that moving against gravity strongly differs from moving along the gravity vector. This directional asymmetry has been attributed to an optimal planning process that optimizes gravity force effects to minimize energy. Yet, only few studies have considered the case of vertical movements in the context of optimal control. What kind of cost is better suited to explain kinematic patterns in the vertical plane? Here, we aimed to understand further how the central nervous system (CNS) plans and controls vertical arm movements. Our reasoning was the following: if the CNS optimizes gravity mechanical effects on the moving limbs, kinematic patterns should change according to the direction and the magnitude of the gravity torque being encountered in the motion. Ten subjects carried out single-joint movements, i.e., rotation around the shoulder (whole arm), elbow (forearm), and wrist (hand) joints, in the vertical plane. Joint kinematics were analyzed and compared with various theoretical optimal model predictions (minimum absolute work-jerk, jerk, torque change, and variance). We found both direction-dependent and joint-dependent variations in several kinematic parameters. Notably, directional asymmetries decreased according to a proximodistal gradient. Numerical simulations revealed that our experimental findings could be attributed to an optimal motor planning (minimum absolute work-jerk) that integrates the direction and the magnitude of gravity torque and minimizes the absolute work of forces (energy-related cost) around each joint. Present results support the general idea that the CNS implements optimal solutions according to the dynamic context of the action.

Transportation Work of Gel Object Done by a Paramecium in the Vertical Plane Pool

2017 ◽  
Author(s):  
Nozomi Hayasaka ◽  
Takumi Kikuchi ◽  
Akitoshi Itoh
Keyword(s):  
Motion Control ◽  
Swimming Speed ◽  
Vertical Plane ◽  
Target Object ◽  
Target Point ◽  
Hard Material ◽  
Vertical Movements ◽  
Upward Direction ◽  
The Difference ◽  
Set Up

We have been investigating how to use microorganisms for bio-micromachines. In this paper, we investigated the motion control property of Paramecium in the vertical plane to prepare the real 3-dimensional motion control. First, we developed a motion control pool for the vertical set up. Basically, the controllability of Paramecium in the vertical plane is not so different to the controllability in the horizontal plane. We can control paramecium very stably for over 100 laps along the star-shaped target route by using this newly made experimental pool. The controllability was improved with the progression of making a circuit. It may relate to the dropping of the swimming speed. The swimming trace, however, showed the peculiarity that related to the vertical movements. The swimming speed of the downward direction is higher than that of the upward direction. The overrun on the downward route was larger than that on the upward route in the vertical plane. It was caused by the difference of the swimming speed on each of routes. Therefore, we developed a new motion control algorithm to decrease this overrun. In our former algorithm, the change timing of the target point was decided by the previous change timing and the previous turning point. In the new algorithm, we change this adjusting method to refer the same target point of the past laps using smoothing value calculated by the integral of the equal ratio attenuation. By using this adjustment method, we succeeded to decrease the overrun. We also investigated the transportability of the object by using motion controlled paramecium in the vertical pool. We found that paramecia often cause their avoiding reaction when they hit object made of hard material. In the case of the object made of soft material, paramecia can push more often and more easily. Therefore, we decided to change the target object from hard plastic to soft gel. We succeeded to transport and drop a gel oval sphere to the target place by manually controlled paramecium in the vertical plane pool.

Late Palaeozoic basins of the southern U.S. continental interior

1982 ◽  
Vol 305 (1489) ◽  
pp. 145-148 ◽  
Keyword(s):  
Plane Strain ◽  
Vertical Plane ◽  
Crustal Thickening ◽  
Local Source ◽  
Lateral Shear ◽  
Progressive Deformation ◽  
Late Palaeozoic ◽  
Continental Interior ◽  
Appalachian Foreland ◽  
Wide Swath

The timing and geometry of late Palaeozoic inhomogenous deformation in the southern U.S. continental interior from the Appalachian foreland of Kentucky-Tennessee through Oklahoma and Texas to the Ancestral Rockies of Colorado-Wyoming-Utah can be definitively linked with a discrete sequence of collisional events in the Appalachian-Ouachita-Marathon orogenic belt to the south (Permian coordinates). A progressive staged collisional sequence beginning in late Mississippian times in the southern Appalachians and culminating in early Permian times in the Marathons led to a progressive deformation of the adjacent craton in a wide swath dominated by right-lateral shear (e.g. Rough Creek Fault zone) by which a Mexican promontory of North America was displaced towards a Pacific ‘free face’. While the deformation in the Appalachian-Marathon belt was dominated by vertical plane strain leading to crustal thickening, the associated continental interior deformation can be averaged as a horizontal plane strain at or near sea level with localized deep extensions (Delaware) and flexural (Arkoma) basins and compressions uplifts (Amarillo-Wichita) giving local source areas.

scholarly journals Full-waveform based microseismic source mechanism studies in the Barnett Shale: Linking microseismicity to reservoir geomechanics

Geophysics ◽  
2014 ◽  
Vol 79 (2) ◽  
pp. KS13-KS30 ◽  
Author(s):  
Fuxian Song ◽  
Norm R. Warpinski ◽  
M. Nafi Toksöz
Keyword(s):  
Seismic Moment ◽  
Source Mechanism ◽  
Fracture Plane ◽  
Barnett Shale ◽  
Natural Fractures ◽  
Data Set ◽  
Full Waveform ◽  
Geomechanical Analysis ◽  
Source Mechanisms ◽  
Well Data

Seismic moment tensors (MTs) of microearthquakes contain important information on the reservoir and fracturing mechanisms. Difficulties arise when attempting to retrieve complete MT with conventional amplitude inversion methods if only one well is available. With the full-waveform approach, near-field information and nondirect waves (i.e., refracted/reflected waves) help stabilize the inversion and retrieve complete MT from the single-well data set. However, for events which are at far field from the monitoring well, a multiple-well data set is required. In this study, we perform the inversion with a dual-array data set from a hydrofracture stimulation in the Barnett Shale. Determining source mechanisms from the inverted MTs requires the use of a source model, which in this case is the tensile earthquake model. The source information derived includes the fault plane solution, slip direction, VP/VS ratio in the focal area and seismic moment. The primary challenge of extracting source parameters from MT is to distinguish the fracture plane from auxiliary plane. We analyze the microseismicity using geomechanical analysis to determine the fracture plane. Furthermore, we investigate the significance of non-DC components by F-test. We also study the influence of velocity model errors, event mislocations, and data noise using synthetic data. The results of source mechanism analysis are presented for the events with good signal-to-noise ratios and low condition numbers. Some events have fracture planes with similar orientations to natural fractures delineated by core analysis, suggesting reactivation of natural fractures. Other events occur as predominantly tensile events along the unperturbed maximum horizontal principal stress direction, indicating an opening mode failure on hydraulic fractures. Microseismic source mechanisms not only reveal important information about fracturing mechanisms, but also allow fracture characterization away from the wellbore, providing critical constraints for understanding fractured reservoirs.

scholarly journals Talker Identification Across Source Mechanisms: Experiments With Laryngeal and Electrolarynx Speech

2014 ◽  
Vol 57 (5) ◽  
pp. 1651-1665 ◽  
Author(s):  
Tyler K. Perrachione ◽  
Cara E. Stepp ◽  
Robert E. Hillman ◽  
Patrick C. M. Wong
Keyword(s):  
Individual Differences ◽  
Healthy Adult ◽  
Voice Quality ◽  
Source Mechanism ◽  
Adult Control ◽  
Source Mechanisms ◽  
Talker Identification ◽  
Vocal Source ◽  
Different Sources ◽  
Better Than

Purpose The purpose of this study was to determine listeners' ability to learn talker identity from speech produced with an electrolarynx, explore source and filter differentiation in talker identification, and describe acoustic-phonetic changes associated with electrolarynx use. Method Healthy adult control listeners learned to identify talkers from speech recordings produced using talkers' normal laryngeal vocal source or an electrolarynx. Listeners' abilities to identify talkers from the trained vocal source (Experiment 1) and generalize this knowledge to the untrained source (Experiment 2) were assessed. Acoustic-phonetic measurements of spectral differences between source mechanisms were performed. Additional listeners attempted to match recordings from different source mechanisms to a single talker (Experiment 3). Results Listeners successfully learned talker identity from electrolarynx speech but less accurately than from laryngeal speech. Listeners were unable to generalize talker identity to the untrained source mechanism. Electrolarynx use resulted in vowels with higher F1 frequencies compared with laryngeal speech. Listeners matched recordings from different sources to a single talker better than chance. Conclusions Electrolarynx speech, although lacking individual differences in voice quality, nevertheless conveys sufficient indexical information related to the vocal filter and articulation for listeners to identify individual talkers. Psychologically, perception of talker identity arises from a “gestalt” of the vocal source and filter.

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