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31.
Anisotropy Effects on Microseismic Event Location 总被引：2，自引：0，他引：2
Seismic anisotropy in sedimentary environments is significant—microseismic waveforms often show strong shear-wave splitting,
with differences reaching 40% between horizontally and vertically-polarized shear-wave velocities. Failure to account for
this anisotropy is shown to result in large microseismic event location errors. A method is presented here for determining
the five elastic parameters of a homogeneous, vertical transverse-isotropic (VTI) model from calibration shot data. The method
can also use data from mining-induced seismic events, which are then simultaneously located. This simple model provides a
good fit to arrival times from coal-environment data, and results in dramatic shifts in interpreted event locations. 相似文献
32.
Sahel Mahdavi Bahram Salehi Cecilia Moloney Weimin Huang Brian Brisco 《International Journal of Digital Earth》2018,11(7):703-729
Speckle degrades the radiometric quality of a Synthetic Aperture Radar (SAR) image. Previous methods for speckle reduction have used a fixed-size window for filtering the entire image. This, however, may not be effective for the entire image, as land covers of different sizes require different filtering windows. In this paper, a novel method is proposed by which each pixel in the image is filtered with a window appropriate for the size of object within it. The real in-phase and the imaginary quadrature components of the SAR images determine the best window size and the pixels in the intensity image are filtered using their own optimal windows. The proposed method is presented for both single- and multi-polarized SAR images, and the results of several common filters that were modified are presented. This approach is applied to two RADARSAT-2 images: one over San Francisco, California, USA and the other over St. John’s, Newfoundland and Labrador, Canada, producing results that were similar to, or outperformed, comparable filters while retaining details and suppressing speckle effectively. While the method was successful for single-look intensity data, it offers great potential for multi-look and amplitude data as well. 相似文献
33.
Satar Mahdevari Kourosh Shahriar Mostafa Sharifzadeh Dwayne D. Tannant 《Arabian Journal of Geosciences》2016,9(18):709
Failure mechanisms of the rock mass in the regions of maximum stress concentrations around a longwall face were assessed. In this respect, seismic events that result from changes in the stress field were analyzed to gain more knowledge about rock failure mechanisms in the proximity of the face area. A deep longwall mine developed at depths of about 3–3.5 km in South Africa was selected as a case study. Seismic moment tensor solutions were obtained for 32 seismic events with moment magnitudes in the range of 0.49 and 2.10. Through moment tensor decomposition, the dominant failure mechanisms were investigated by drawing focal mechanism plots. Further analysis was implemented by depicting the corresponding 3D radiation patterns of P-wave particle motions. Although the results cover various failure mechanisms, the dominant mechanisms are shear, implosional, and compressional failures. According to the results, most of the maximum principal stresses in the mine are compressive and oriented nearly vertical, which are in accordance with the gravitational collapses of the mined out areas. The results obtained from this research show that measuring and analyzing mining-induced seismicity can be a reliable measure to characterize the dominant failure mechanisms in a nondestructive manner and to provide a useful assessment of the stability of the longwall face in advance of extraction. 相似文献
34.
China Ocean Engineering - Conventional design of pier structures is based on the assumption of fully rigid joints. In practice, the real connections are semi-rigid that cause changes in dynamic... 相似文献
35.
Environmental impact assessment of open pit mining in Iran 总被引：2，自引：0，他引：2
Mining is widely regarded as having adverse effects on environment of both magnitude and diversity. Some of these effects
include erosion, formation of sinkhole, biodiversity loss and contamination of groundwater by chemical from the mining process
in general and open-pit mining in particular. As such, a repeatable process to evaluate these effects primarily aims to diminish
them. This paper applies Folchi method to evaluate the impact of open-pit mining in four Iranian mines that lacked previous
geo-environmental assessment. Having key geologic resources, these mines are: Mouteh gold mine, Gol-e-Gohar and Chogart iron
mines, and Sarcheshmeh copper mine. The environmental components can be defined as public health and safety, social relationships,
air and water quality, flora and fauna hence, various impacting factors from the mining activities were estimated for each
environmental component. For this purpose, each impacting factor was first given a magnitude, based solely on the range of
possible scenarios. Thereafter, a matrix of weighted factors was derived to systematically quantify and normalize the effects
of each impacting factor. The overall impact upon each individual environmental component was then calculated by summing the
weighted rates. Here, Folchi method was applied to evaluate those environmental conditions. Based on the acquired results,
the present paper finally concludes that amongst four case histories in Iran, Sarcheshmeh copper mine significantly affects
the environment, with critical level of air pollution there. 相似文献
36.
Land subsidence caused by the excessive use of groundwater resources has caused serious damage to Rafsanjan area. In this study, using finite element method, a 2D plain strain simulation of land subsidence has been conducted. A linear elastic constitutive law has been used for the simulation of the soil material skeleton. Actual water level during the analysis period has been modeled via specifying nodal water pressure at piezometer wells situation. The solution procedure consists of two parts. First, an initial static analysis is carried out in order to find initial steady-state solution for the pore pressure and stress distribution. Then, the above solution is used as initial condition for dynamic computation of consolidation equations during pumpage period. Tectonic effect has been considered as a rigid body motion. Numerical results showed that if the rate of pumpage remains constant in the future, settlement due to water withdrawal near Rafsanjan city will reach up to 110 cm by the year 2022. 相似文献
37.
Shahriar Negahdaripour Caroline Barufaldi Ali Khamene 《Oceanic Engineering, IEEE Journal of》2006,31(3):533-550
Estimating the relative positions and (or) trajectory of a camera from video images is a fundamental problem in motion vision. Of special relevance is the closed-form solution for planar scenes, for processing fly-over imagery from airborne and underwater robotics platforms, automated airplane landing utilizing runway landmarks, photomosaicing, etc. However, the method's robustness can break down in certain scenarios, e.g., due to inherent translation-rotation ambiguity of visual motion with short baselines and narrow field of view. The robustness can be improved by devising methods that compute a smaller set of motion parameters, utilizing other sensors to measure the remaining components. This paper addressed key issues in six degrees of freedom positioning from fly-over imagery by integrating vision with rotational angle sensors. First, we propose and utilize robust closed-form solutions for estimating the motion and orientation of a planar surface from the image flow variations up to first order, given measurements of pitch and roll motions. We also describe a calibration technique to enable the integration of angle sensor and visual measurements. Next, an error analysis enables us to evaluate the impact of inaccurate pitch and roll measurements on the estimates from the new closed-form solutions. Finally, the performance of our new methods and the integrated positioning system are evaluated in various experiments with synthetic and real data 相似文献
38.
On retrieving patterns in environmental sensor data 总被引：1，自引：0，他引：1
As many sensor networks are currently being deployed for environmental monitoring, there is a growing need to develop systems
and applications for managing, processing and retrieving massive amounts of data generated from those networks. In this research,
a query answering system with pattern mining techniques is investigated specifically for marine sensor data. We consider three
applications of pattern mining: similar pattern search, predictive query and query by clustering. In pattern mining for query
answering, we adopt the dynamic time warping (DTW) method for similarity measurement. We also propose the use of a query relaxation
approach that recommends users change parameters of a given query to get an answer. Finally, we show implementation results
of pattern query answering in a marine sensor network deployed in the South East of Tasmania, Australia. Pattern query answering
system benefits in accessing and discovering knowledge from sensor data for decision making purposes. 相似文献
39.
A vast portion of Newfoundland and Labrador (NL) is covered by wetland areas. Notably, it is the only province in Atlantic Canada that does not have a wetland inventory system. Wetlands are important areas of research because they play a pivotal role in ecological conservation and impact human activities in the province. Therefore, classifying wetland types and monitoring their changes are crucial tasks recommended for the province. In this study, wetlands in five pilot sites, distributed across NL, were classified using the integration of aerial imagery, Synthetic Aperture Radar, and optical satellite data. First, each study area was segmented using the object-based method, and then various spectral and polarimetric features were evaluated to select the best features for identifying wetland classes using the Random Forest algorithm. The accuracies of the classifications were assessed by the parameters obtained from confusion matrices, and the overall accuracies varied between 81% and 91%. Moreover, the average producer and user accuracies for wetland classes, considering all pilot sites, were 71% and 72%, respectively. Since the proposed methodology demonstrated high accuracies for wetland classification in different study areas with various ecological characteristics, the application of future classifications in other areas of interest is promising. 相似文献
40.
Jian-qiang?ZhangEmail author Rong-kun?Liu Wei?Deng Narendra?Raj?Khanal Deo?Raj?Gurung Manchiraju?Sri?Ramachandra?Murthy Shahriar?Wahid 《山地科学学报》2016,13(10):1711-1722
Koshi River basin, which lies in the Central Himalayas with an area of 71,500 km2, is an important trans-boundary river basin shared by China, Nepal and India. Yet, landslide-prone areas are all located in China and Nepal, imposing alarming risks of widespread damages to property and loss of human life in both countries. Against this backdrop, this research, by utilizing remote sensing images and topographic maps, has identified a total number of 6877 landslides for the past 23 years and further examined their distribution, characteristics and causes. Analysis shows that the two-step topography in the Himalayan region has a considerable effect on the distribution of landslides in this area. Dense distribution of landslides falls into two regions: the Lesser Himalaya(mostly small and medium size landslides in east-west direction) and the TransitionBelt(mostly large and medium size landslides along the river in north-south direction). Landslides decrease against the elevation while the southern slopes of the Himalayas have more landslides than its northern side. Change analysis was carried out by comparing landslide distribution data of 1992, 2010 and 2015 in the Koshi River basin. The rainfallinduced landslides, usually small and shallow and occurring more frequently in regions with an elevation lower than 1000 m, are common in the south and south-east slopes due to heavy precipitation in the region, and are more prone to the slope gradient of 20°~30°. Most of them are distributed in Proterozoic stratum(Pt3ε, Pt3 and Pt2-3) and Quaternary stratum. While for earthquake-induced landslides, they are more prone to higher elevations(2000~3000 m) and steeper slopes(40°~50°). 相似文献