by Deepak Singh, D. N. Pandey and Usha Mina
Original Research
The whole world from time to time is exposed to the unpredictable disaster called Earthquake which causes immense damage to the infrastructure, life and injury to the people. The present manuscript tries to discuss different aspects of the Earthquake in the present scenario in India and the role of government and its policies, society, schools and technology for the prevention and mitigation measures and impact on biogeochemistry of the earth crust. Due to location of India in tropics and happening of plate tectonic activities under and around the Indian plates has made India prone to the different types of disaster of which one of them is the Earthquake. The prediction of Earthquake is still not possible accurately. In India, during the 10thFive year plan, there has been paradigm shift in the laws and policies related to the disaster management. A separate act called Disaster Management Act-2005, has been passed by the Parliament of India. This act provides institutional, legal, financial and coordination mechanisms at the national, state, district and local levels for management of all types of disaster happening in India. This law made the role of government from relief oriented measures to the prevention and preparedness. During the Earthquake, there occurs a different type of impacts on the Biogeochemistry of the earth crust. Among them, there are the impacts on biodiversity of living organisms, variation in the water levels, folding and faulting in the crust of the Earth and generation of sea waves called Tsunami etc. Technology in the form of remote sensing and GIS can play important role and can be used before and after the occurrence of Earthquake for proper management. The Earthquake is a disaster which is unpredictable, untimely and we lack of mechanism and technology to predict its time of happening precisely. With regard to Earthquake disaster, we can only prepare our self, take preventive and preparedness measures, so that there is less damage to infrastructure and loss of life. This can be achieved by investing more in research and development of tools for prediction, proper understanding of Earthquake phenomenon, along with it there is need to concentrate more on prevention, preparedness and mitigation before and quick relief to the people after the occurrence of Earthquake.
Journal of Geosciences and Geomatics. 2019, 7(2), 88-96. DOI: 10.12691/jgg-7-2-5
Pub. Date: April 26, 2019
6889 Views1265 Downloads
by Danra Moh Guela Guy Basile, Tchameni Rigobert, Daouda Dawaï, Fosso Tchunte Periclex Martial, Awé Salomon and Bisségué Jean Claude
Original Research
Field studies, Landsats 8 OLI/TIRS processing and the digital elevation model of SRTM images permit us to map the Mokong area, region situated in arid zone and located to the Northen part of the central African Orogenic belt in Cameroun. The use of Landsat’s number 3 band of made it possible to highlight the lineaments. It has been noticed after analyses that the maximum number of lineaments are oriented N-S direction. The second major trends of lineaments in the study area are respectively, ENE-WSW, E-W and SSE-NNW. The landsat OLI/TIRS processing (colorful composition, band math, and principal component analysis) are permitted to discriminate four mains rocks types: gneisses-amphibolite; biotite granite, diorite-granodiorite and tonalite. All those facies are partially covered by alluvial deposits in the southern erea. The digital elevation model has permitted to identify some volcanic cover. The method used in this work offers promising prospects for geological mapping of arid regions where there is usually little map, because with this method, the time is reduced and the result is more precise.
Journal of Geosciences and Geomatics. 2019, 7(2), 80-87. DOI: 10.12691/jgg-7-2-4
Pub. Date: April 26, 2019
12456 Views1699 Downloads
by Nwankwo C.N. and Ogagarue D.O.
Original Research
Seismic refraction tomography was carried out in Ebem community, Ohafia, eastern Nigeria, which recently experienced erosional landslide. The aim was to determine the near surface characteristics in the area, offer possible geologic explanation to the frequent landslides which occur in the area and provide information on potential slide zones to mitigate future disasters. A total of three seismic refraction profiles were carried out using a 12-channel ABEM Terrace MK III digital seismograph with inter-channel spacing of 10 m. Shots were generated by means of a 6 kg sledge hammer and metal plates at 23.5 m before the first and after the last geophone group respectively, and at every geophone station, giving a total length of 157 m for each profile. Velocity structure from the study shows that the area is made up of three different layers on account of velocity distribution, which includes a top layer of unconsolidated, low velocity dry sands assumed to be weathering layer with velocity ranging from about 412 m/s to 1,300 m/s. This layer varies in thickness from about 9 m at the flanks to about 35 m at the center, creating a thick zone of low velocity at the center. This is underlain by a very thin, apparently more compacted sub-weathering layer containing a mixture of sands and clay in which velocity and thickness vary from about 1,300 m/s to 3,000 m/s, and 2,31 m to 3.01 m respectively. Compressional velocity in the area varies from about 412 m/s to about 4.090 m/s, and velocities in the bedrock generally exceed 3,000 m/s; the velocity generally increasing with depth from the surface. The results suggest that the frequent landslides in the area are likely the result of the thick, unconsolidated and permeable dry sands underneath the surface which presumably acts as a sinkhole for surface water run-offs orchestrated by the frequent rainfall which is common in the area. Areas with the highest thickness of weathering are the most vulnerable to sliding in the area.
Journal of Geosciences and Geomatics. 2019, 7(2), 73-79. DOI: 10.12691/jgg-7-2-3
Pub. Date: March 22, 2019
8289 Views1098 Downloads
by Ogagarue D.O. and Nwankwo C.N
Original Research
In addition to de-spiking, gun delay correction, correction for spherical spreading and earth’s absorption, gun and cable correction, zero-phasing, noise attenuation and correction for time shifts between sail lines due to changes in velocity of the water column, multiple elimination is the other important true relative amplitude processing routine desired to produce seismic gathers consistent with DHI and AVO analysis to de-risk the presence of hydrocarbon interpreted from seismic data. Multiple problems associated with seismic data acquired in the Niger Delta offshore are those due mainly to the free air-water interface and the seabed, and their presence constitute noise in the seismic dataset. In this study, we employed an approach in which we convolved all possible source and receiver peglegs for every multiple event that strikes the free surface irrespective of its path in the subsurface to model the multiple wave field in a 3D sense, in a partially processed pre-migration seismic data acquired in the Niger Delta deep offshore. The method of adaptive subtraction was then used to eliminate the modeled multiples from the dataset. Un-like other demultiple techniques such as tau-p deconvolution and radon, our multiple modeling and subtraction techniques do not require prior knowledge of the subsurface geology in terms of the velocity and reflectivity of the multiple wave field. The aim of the study was to improve the overall quality of the seismic data and signal-to-noise ratio, in addition to the DHI and AVO compliant gathers output from the process. The approach was successful and effective in removal of the free, air-water surface multiples from the dataset.
Journal of Geosciences and Geomatics. 2019, 7(2), 66-72. DOI: 10.12691/jgg-7-2-2
Pub. Date: March 13, 2019
5549 Views1400 Downloads
by Jean Jacques Nguimbous-Kouoh, Dieudonné Minyem, Richard Tanwi Ghogomu, Simon Ngos III and Eliezer Manguelle-Dicoum
Original Research
In the Far-North Region of Cameroon, the high rate of weathering and erosion of rocks do not allow to map the hydrological and geological structures in the field. This paper aims to test the combined use of field topographic data and Shuttler Radar Topography Mission (SRTM) data to define watershed morphometry, highlight the different erosion factors, and characterize the structural lineaments of the Mayo-Kani Division, within the Far-North Region of Cameroon. All these are done using; watersheds, hydrographic network, slopes, manual lineaments and automatic lineaments maps. These treatment techniques used (filtering, enhancement and slope analyses) allows: to morphologically characterize the ten identified Mayo-Kani watersheds, to measure the erodibility rate of the watersheds using the Universal Soil Loss Equation (USLE) and to compute the fracture maps. This last operation was validated using ground truth field observations and the literature review. Fracture networks were analyzed using statistical analysis techniques by studying fracture length distribution laws.
Journal of Geosciences and Geomatics. 2019, 7(2), 54-65. DOI: 10.12691/jgg-7-2-1
Pub. Date: March 08, 2019
14726 Views2016 Downloads