Applications of hybrid genetic algorithms in seismic tomography     

Pantelis Soupios  Irfan Akca  Petros Mpogiatzis  Ahmet T. Basokur  Constantinos Papazachos 《Journal of Applied Geophysics》2011,75(3):479-489

Almost all earth sciences inverse problems are nonlinear and involve a large number of unknown parameters, making the application of analytical inversion methods quite restrictive. In practice, most analytical methods are local in nature and rely on a linearized form of the problem equations, adopting an iterative procedure which typically employs partial derivatives in order to optimize the starting (initial) model by minimizing a misfit (penalty) function. Unfortunately, especially for highly non-linear cases, the final model strongly depends on the initial model, hence it is prone to solution-entrapment in local minima of the misfit function, while the derivative calculation is often computationally inefficient and creates instabilities when numerical approximations are used. An alternative is to employ global techniques which do not rely on partial derivatives, are independent of the misfit form and are computationally robust. Such methods employ pseudo-randomly generated models (sampling an appropriately selected section of the model space) which are assessed in terms of their data-fit. A typical example is the class of methods known as genetic algorithms (GA), which achieves the aforementioned approximation through model representation and manipulations, and has attracted the attention of the earth sciences community during the last decade, with several applications already presented for several geophysical problems.In this paper, we examine the efficiency of the combination of the typical regularized least-squares and genetic methods for a typical seismic tomography problem. The proposed approach combines a local (LOM) and a global (GOM) optimization method, in an attempt to overcome the limitations of each individual approach, such as local minima and slow convergence, respectively. The potential of both optimization methods is tested and compared, both independently and jointly, using the several test models and synthetic refraction travel-time date sets that employ the same experimental geometry, wavelength and geometrical characteristics of the model anomalies. Moreover, real data from a crosswell tomographic project for the subsurface mapping of an ancient wall foundation are used for testing the efficiency of the proposed algorithm. The results show that the combined use of both methods can exploit the benefits of each approach, leading to improved final models and producing realistic velocity models, without significantly increasing the required computation time.  相似文献   

Experimental and Statistical Evaluation of Cutting Methods in Relation to Specific Energy and Rock Properties     

Irfan Celal Engin  Fatih Bayram  Nazmi Erhan Yasitli 《Rock Mechanics and Rock Engineering》2013,46(4):755-766

In a processing plant, natural stone can be cut by methods such as circular sawing (CS), frame sawing (FS), water jet cutting (WJC) and abrasive water jet cutting (AWJC). The efficiency of cutting systems can be compared using various parameters. In this study, the specific energy values were determined and compared to evaluate the efficiency of rock-cutting methods. Rock-cutting experiments were performed on 12 different types of rock samples using a circular sawing machine and an AWJC machine. The experimental results showed that the specific energy values in AWJC were generally higher than in CS. In addition, the relationships between specific energy values and rock properties were explained in this study. The Shore hardness and abrasion resistance were found to be strongly related to the specific energy values, and according to these parameters prediction charts of specific energy values were created.  相似文献   

Dynamic Development of Hydrofracture     

Irfan Ghani  Daniel Koehn  Renaud Toussaint  Cees Willem Passchier 《Pure and Applied Geophysics》2013,170(11):1685-1703

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Machine Learning Approach to Predict Sediment Load – A Case Study     

Hazi Md. Azamathulla  Aminuddin Ab. Ghani  Chun Kiat Chang  Zorkeflee Abu Hasan  Nor Azazi Zakaria 《洁净——土壤、空气、水》2010,38(10):969-976

In this study, a novel machine learning technique called the support vector machine (SVM) method is proposed as a new predictive model to predict sediment loads in three Malaysian rivers. The SVM is employed without any restriction to an extensive database compiled from measurements in the Muda, Langat, and Kurau rivers. The SVM technique demonstrated a superior performance compared to other traditional sediment‐load methods. The coefficient of determination, 0.958, and the mean square error, 0.0698, of the SVM method are higher than those of the traditional method. The performance of the SVM method demonstrates its predictive capability and the possibility of the generalization of the model to nonlinear problems for river engineering applications.  相似文献   

ELRIS2D: A MATLAB Package for the 2D Inversion of DC Resistivity/IP Data     

Irfan Akca 《Acta Geophysica》2016,64(2):443-462

ELRIS2D is an open source code written in MATLAB for the two-dimensional inversion of direct current resistivity (DCR) and time domain induced polarization (IP) data. The user interface of the program is designed for functionality and ease of use. All available settings of the program can be reached from the main window. The subsurface is discre-tized using a hybrid mesh generated by the combination of structured and unstructured meshes, which reduces the computational cost of the whole inversion procedure. The inversion routine is based on the smoothness constrained least squares method. In order to verify the program, responses of two test models and field data sets were inverted. The models inverted from the synthetic data sets are consistent with the original test models in both DC resistivity and IP cases. A field data set acquired in an archaeological site is also used for the verification of outcomes of the program in comparison with the excavation results.  相似文献   

Detection of water infiltration and deformation of unsaturated soils by elastic wave velocity   总被引：1，自引：1，他引：0  

Yulong Chen  Taro Uchimura  Muhammad Irfan  Dong Huang  Jiren Xie 《Landslides》2017,14(5):1715-1730

Intense rainfall is the most important landslide trigger. In many mountainous environments of the world, heavy rainfall has caused many landslides and slope failures in a matter of seconds without warning. Therefore, an early warning system can be an effective measure to reduce the damage caused by landslides and slope failures by facilitating the timely evacuation of people from landslide-prone areas. In this study, we propose an idea to correlate soil moisture changes and deformations in slope surface by means of elastic wave propagation in soil. Constant shear stress drained triaxial tests where water was infiltrated from the bottom of specimen until failure, and slope model tests under artificial rainfall were performed to investigate the response of elastic wave velocities during pre-failure phases of rainwater infiltration and deformation. Analysis of the results has established that the elastic wave velocity continuously decreases in response of moisture content and deformation, and there was a distinct surge in the decrease rate of wave velocity when failure was initiated. Possible mechanisms were interpreted based on the test results. It is proposed that a warning be issued at switch of wave velocity decrease rate. This approach can thus serve as the basis of an early warning system for landslides and slope failure considering both moisture content and deformation.  相似文献   

Imagery of the metamorphic bedrock roof of the Sahel active fault in the Sablettes (Algiers) reclaimed area by ambient vibration HVSR     

Mohamed Yacine Tebbouche  Djamel Machane  Souhila Chabane  El-Hadi Oubaiche  Aghiles Abdelghani Meziani  Dalila Ait Benamar  Hakim Moulouel  Ghani Cheikh Lounis  Rabah Bensalem  Abderrahmane Bendaoud 《Arabian Journal of Geosciences》2017,10(13):292

The Sablettes (Algiers) coastal reclaimed fringe region, located on the hanging wall of the Sahel active fault, is subject to different types of geological hazard such as flood and tsunami, coastal uplift, earthquake, liquefaction, landslide, and site effects. In this present work, we used ambient vibration HVSR for imaging the bedrock. The thickness of the sedimentary column under the backfill layer is unknown, and the coastal reclaimed areas are prone to strong amplification of seismic waves. The determination of the depth of the metamorphic base allowed us to establish a mapping of the bedrock roof surface. The 3D representation of this surface enabled us to present models of tectonic structures in this basement (i.e., fault, fold). This analysis will make it possible to make better evaluation of the amplification after having determined the depth of the metamorphic basement exceeding 240 m, which is supposed to have velocities close to those of the seismological basement, as well as the thicknesses of the different layers surmounting it.  相似文献   

Cadmium (Cd) concentration in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>) grown in Cd-spiked soil varies with the doses and biochar feedstock     

Muhammad Zia ur Rehman  Muhammad Rizwan  Shafaqat Ali  Muhammad Irfan Sohail  Amjad Hussain  Muhammad Farooq Qayyum  Hinnan Khalid  Muhammad Zeeshan  Naveeda Majid 《Arabian Journal of Geosciences》2018,11(21):685

Biochar is considered a promising amendment for the reduction of metal concentration in plants; however, the effects of biochar in terms of dose and feedstock on metal uptake by plants remain widely unclear. In the current study, three individual biochars were prepared at 450 °C from different feedstocks (wheat straw, sukh chain (Pongamia pinnata), and cotton sticks). The main aim was to evaluate their ability to remediate cadmium (Cd)-spiked soil in terms of growth response and Cd uptake by wheat (Triticum aestivum) tissues. Biochars were separately applied at 0, 1, and 2% (w/w) in Cd-spiked soil and wheat was grown until maturity in pots and then morphological and physiological parameters and Cd concentrations in grains, roots, and shoots were determined. The post-harvest soil was analyzed for extractable Cd concentrations. Plants grown in Cd-spiked soil treated with biochars had higher seed germination, lengths of roots, shoots, and spikes, grains per spike and leaf relative water contents, chlorophyll contents, and dry weight of roots, shoots, and grains as compared to the untreated control. Biochar treatments significantly decreased the Cd concentrations in shoots, roots, and grains as well as total Cd uptake by grains. Soil extractable Cd concentrations were significantly decreased with biochar treatments. The application of 2.0% wheat straw biochar was the most efficient treatment in increasing grain yield and decreasing Cd in grains as well as soil extractable Cd than the other two biochars and doses applied.  相似文献   

Numerical Analysis of Himalayan Rock Tunnels under Static and Blast Loading     

Zaid  Mohammad  Shah  Irfan Ahmad 《Geotechnical and Geological Engineering》2021,39(7):5063-5083

Geotechnical and Geological Engineering - Tunnels have been the necessary element of the modern construction industry. Due to their importance for the infrastructural and economic point of view,...  相似文献   

Time series assessment on landslide occurrences in an area undergoing development          下载免费PDF全文

Norbert Simon  Michael Crozier  Mairead de Roiste  Abdul Ghani Rafek  Rodeano Roslee 《Singapore journal of tropical geography》2015,36(1):98-111

This study assesses the influence of development on landslide occurrences in a rapidly developing area, Kota Kinabalu in Sabah Malaysia, across three assessment years (1978, 1994 and 2010). Two development indicators, land use and road density, were used to measure the influence of development on landslide occurrence. Land use was classified into four categories (barren, forest, developed and other), and road density was classified into low (< 50 m/40 000 m²), moderate (50–150 m/40 000 m²) and high (> 150 m/40 000 m²). Landslide density analysis was used to calculate the concentration of landslide for the different land use and road density categories. The number of landslides in developed areas increased from 19 landslides/100 km² in 1978, to 29 landslides/100 km² in 1994 and to 50 landslides/100 km² in 2010, mirroring an increase in land use for development purposes from 8 per cent in 1978 to 27 per cent in 2010. Landslide density also gradually increased in the high road density class from 10 landslides/100 km² in 1978, to 30 landslides/100 km² in 1994 and 62 landslides/100 km² in 2010. These results show that road construction activities influence landslide occurrences.  相似文献