40Ar/39Ar dating of the Jiali and Gaoligong shear zones: Implications for crustal deformation around the Eastern Himalayan Syntaxis     

Te-Hsien Lin  Ching-Hua Lo  Sun-Lin Chung  Fang-Jui Hsu  Meng-Wan Yeh  Tung-Yi Lee  Jian-Qing Ji  Yi-Zhau Wang  Dunyi Liu 《Journal of Asian Earth Sciences》2009,34(5):674-685

We conducted a comprehensive ⁴⁰Ar/³⁹Ar geochronological study of the Jiali and Gaoligong shear zones to obtain a better understanding of crustal deformation and tectonic evolution around the Eastern Himalayan Syntaxis (EHS). The new age data reveal that the main phase of deformation in the Jiali and Gaoligong shear zones occurred from 22 to 11 Ma and from 18 to 13 Ma, respectively. Structural data collected during this study indicate that the Jiali shear zone underwent a change in shear sense from sinistral to dextral during its movement history. Based on a comparison with the deformation histories of other major shear zones in the region, we argue that the initial sinistral motion recorded by the Jiali shear zone was coincident with that of the Ailao Shan–Red River shear zone, which marked the northern boundary of the southeastward extrusion of the Indochina block during the Early Miocene. From the Middle Miocene (～18 Ma), the Jiali shear zone changed to dextral displacement, becoming linked with the dextral Gaoligong shear zone that developed as a consequence of continued northward indentation of the Indian continent into Asia. Since this time, the Jiali and Gaoligong shear zones have been united, defining the southwestern boundary of the EHS during clockwise rotation of the eastward-extruding Tibetan block, as revealed by recent GPS data. The temporal change in regional deformation pattern from southeastward block extrusion to clockwise rotation of crustal fragments may have played an important role in the development of the eastern Himalayan drainage system around the EHS.  相似文献   

A constant key length coding scheme for linear quadtrees     

Henry Ker–Chang Chang  Chung–Yu Liou 《International journal of geographical information science》2013,27(2):205-218

ABSTRACT

Although the linear quadtree is popular in both image processing and GIS, most linear quadtree coding methods need in representation a bit length that is proportional to the resolution of images; the proportionality factor is replaced with a constant bit length that induces a more compact linear quadtree. We propose a linear quadtree coding scheme named constant key length quadtree coding (CKQC) that has advantages of easy implementation and decreased memory requirements. The proposed CKQC scheme is developed on the bases of node classification, order of traversal with breadth first and the Morton sequence. The major characteristic is to apply a constant bit length to construct quaternary codes. The bit length of each quaternary code is constant, either four or eight bits, no matter what the resolution of a raster image. In terms of memory space required and duration complexities, the overall performance is analyzed and compared with other methods to demonstrate the superiority of the proposed CKQC scheme. Several experimental results validate the applicability of the proposed scheme.  相似文献   

A new methodology for measuring coastline recession using buffering and non‐linear least squares estimation     

Joon Heo  Jung Hwan Kim  Jin Woo Kim 《International journal of geographical information science》2013,27(9):1165-1177

Coastline recession is one of the best indicators of coastal erosion. Three methods for computing coastline recession – the baseline approach, the dynamic segmentation approach and the area‐based approach – have been used, each of which has one or more drawbacks. To overcome these problems, a new methodology for measuring coastline recession is proposed, using buffering and non‐linear least squares estimation. The proposed method was compared with the three existing methods with respect to two simulated cases and two real coastlines. Test results confirmed that the new method is more reliable than the three other methods, all of which are susceptible to variability of recession, scale, number of line segments, length of coastlines and direction of the baseline. The proposed method, incorporating two physically meaningful values – magnitude and variability of coastline recession according to the mean and standard deviation of coastline offsets, respectively – presents itself as an effective alternative method of assessing coastline recession.  相似文献   

2D Laplace-Domain Waveform Inversion of Field Data Using a Power Objective Function     

Eunjin Park  Wansoo Ha  Wookeen Chung  Changsoo Shin  Dong-Joo Min 《Pure and Applied Geophysics》2013,170(12):2075-2085

The wavefield in the Laplace domain has a very small amplitude except only near the source point. In order to deal with this characteristic, the logarithmic objective function has been used in many Laplace domain inversion studies. The Laplace-domain waveform inversion using the logarithmic objective function has fewer local minima than the time- or frequency domain inversion. Recently, the power objective function was suggested as an alternative to the logarithmic objective function in the Laplace domain. Since amplitudes of wavefields are very small generally, a power <1 amplifies the wavefields especially at large offset. Therefore, the power objective function can enhance the Laplace-domain inversion results. In previous studies about synthetic datasets, it is confirmed that the inversion using a power objective function shows a similar result when compared with the inversion using a logarithmic objective function. In this paper, we apply an inversion algorithm using a power objective function to field datasets. We perform the waveform inversion using the power objective function and compare the result obtained by the logarithmic objective function. The Gulf of Mexico dataset is used for the comparison. When we use a power objective function in the inversion algorithm, it is important to choose the appropriate exponent. By testing the various exponents, we can select the range of the exponent from 5 × 10^?3 to 5 × 10^?8 in the Gulf of Mexico dataset. The results obtained from the power objective function with appropriate exponent are very similar to the results of the logarithmic objective function. Even though we do not get better results than the conventional method, we can confirm the possibility of applying the power objective function for field data. In addition, the power objective function shows good results in spite of little difference in the amplitude of the wavefield. Based on these results, we can expect that the power objective function will produce good results from the data with a small amplitude difference. Also, it can partially be utilized at the sections where the amplitude difference is very small.  相似文献   

Application of a multi‐temporal,LiDAR‐derived,digital terrain model in a landslide‐volume estimation     

Chih‐Ming Tseng  Ching‐Weei Lin  Colin P. Stark  Jin‐Kin Liu  Li‐Yuan Fei  Yu‐Chung Hsieh 《地球表面变化过程与地形》2013,38(13):1587-1601

Sediments produced by landslides are crucial in the sediment yield of a catchment, debris flow forecasting, and related hazard assessment. On a regional scale, however, it is difficult and time consuming to measure the volumes of such sediment. This paper uses a LiDAR‐derived digital terrain model (DTM) taken in 2005 and 2010 (at 2 m resolution) to accurately obtain landslide‐induced sediment volumes that resulted from a single catastrophic typhoon event in a heavily forested mountainous area of Taiwan. The landslides induced by Typhoon Morakot are mapped by comparison of 25 cm resolution aerial photographs taken before and after the typhoon in an 83.6 km² study area. Each landslide volume is calculated by subtraction of the 2005 DTM from the 2010 DTM, and the scaling relationship between landslide area and its volume are further regressed. The relationship between volume and area are also determined for all the disturbed areas (V_L = 0.452A_L^1.242) and for the crown areas of the landslides (V_L = 2.510A_L^1.206). The uncertainty in estimated volume caused by use of the LiDAR DTMs is discussed, and the error in absolute volume estimation for landslides with an area >10⁵ m² is within 20%. The volume–area relationship obtained in this study is also validated in 11 small to medium‐sized catchments located outside the study area, and there is good agreement between the calculation from DTMs and the regression formula. By comparison of debris volumes estimated in this study with previous work, it is found that a wider volume variation exists that is directly proportional to the landslide area, especially under a higher scaling exponent. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Combined analyses of chemometrics and kriging for identifying groundwater contamination sources and origins at the Masan coastal area in Korea   总被引：2，自引：2，他引：0  

Tae Hyung Kim  Sang Yong Chung  Namsik Park  Se-Yeong Hamm  Seung Yeop Lee  Byung-Woo Kim 《Environmental Earth Sciences》2012,67(5):1373-1388

Hydrogeochemical analyses including the basic statistics of chemical components, Piper??s trilinear diagram, and Mazor??s compositional bivariate diagram revealed that the main source and origin of groundwater contamination was seawater intrusion in the study area. However, the other sources and origins of groundwater contamination could be found by the combined analyses of chemometrics and kriging. Cluster analysis was helpful for the classification on the basis of the contamination characteristics of groundwater quality; however, it was not sufficient for the apportionment of groundwater contamination sources. Factor analysis (FA) determined three factors with 81.07% in total variance: Factor 1 for seawater contamination, Factor 2 for nitrate contamination, and Factor 3 for iron contamination. Factor analysis determined the sources of groundwater contamination; however, it could not discover the origins of contaminants except Factor 1. In backward stepwise mode, discriminant analysis decreased the number of parameters from 18 to 6 in discriminating the contaminant type with 96.2% correctness. TDS, Ca, NO₃, Mn, Fe, and Br were the most significant parameters for the discrimination of contaminants. Kriging analysis was very useful for the understanding of correlation and similarity between contaminants and factors of FA, and for the investigation of contaminant origins. It also showed that the similarity between factor scores and contaminant concentrations was proportional to the magnitudes of factor loadings for contaminants. This study represented that the combined analyses of chemometrics and kriging were very indispensable to the identification of groundwater contamination sources and origins, as well as for the spatial classification and assessment of groundwater quality.  相似文献   

A linear projection for the timing of unprecedented climate in Korea     

Ho-Jeong Shin  Chan Joo Jang  Il-Ung Chung 《Asia-Pacific Journal of Atmospheric Sciences》2017,53(4):411-419

Recently we have had abnormal weather events worldwide that are attributed by climate scientists to the global warming induced by human activities. If the global warming continues in the future and such events occur more frequently and someday become normal, we will have an unprecedented climate. This study intends to answer when we will have an unprecedented warm climate, focusing more on the regional characteristics of the timing of unprecedented climate. Using an in-situ observational data from weather stations of annual-mean surface air temperature in Korea from 1973 to 2015, we estimate a timing of unprecedented climate with a linear regression method. Based on the in-situ data with statistically significant warming trends at 95% confidence level, an unprecedented climate in Korea is projected to occur first in Cheongju by 2043 and last in Haenam by 2168. This 125-year gap in the timing indicates that a regional difference in timing of unprecedented climate is considerably large in Korea. Despite the high sensitivity of linear estimation to the data period and resolution, our findings on the large regional difference in timing of unprecedented climate can give an insight into making policies for climate change mitigation and adaptation, not only for the central government but for provincial governments.  相似文献   

Migrating magmatism in a continental arc: Geodynamics of the Eastern Mediterranean revisited   总被引：1，自引：0，他引：1  

Yener Eyuboglu  M. Santosh  Francis O. Dudas  Sun-Lin Chung  Enver Akaryal&#x; 《Journal of Geodynamics》2011,52(1):2-15

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Transition from shoshonitic to adakitic magmatism in the eastern Pontides,NE Turkey: Implications for slab window melting     

Yener Eyuboglu  Sun-Lin Chung  M. Santosh  Francis O. Dudas  Enver Akaryalı 《Gondwana Research》2011,19(2):413-429

The formation of the eastern Pontides orogenic belt has been widely assigned to a northward subduction of the Neotethyan oceanic slab during the late Mesozoic–Cenozoic. Here we provide an alternate model based on new geological, geochemical and isotopic data. The magmatic activity in the far south of the belt started in the early Campanian with shoshonitic trachyandesites and associated pyroclastics. This sequence is covered by the late Campanian–early Maastrichtian reefal limestones and another stage of high-K volcanism represented by analcimized leucite-rich ultrapotassic rocks of the Maastrichtian–early Paleocene (?) ages. The shoshonitic and ultrapotassic rocks, with K₂O contents ranging from 0.26 to 6.95 wt.%, display broadly similar rare earth and multi-element distribution patterns. Both rock types are enriched in LILE and LREE and depleted in HFSE (Nb, Ta and Ti), suggesting a subduction-enriched mantle source for the magma generation. Subsequently, during the late Paleocene, a stage of acidic magmatism (SiO₂ of 53.25–73.61 wt.%) that shows adakitic geochemical characteristics including high Sr/Y (46–416) and La/Yb (11–51) and low Y (2.6–12.2 ppm), is documented characterized by melting of a mafic source such as the MORB crust with garnet in the residue. The adakitic magmatism began at ~ 56 Ma and migrated toward the north through time, culminating with porphyritic andesites (~ 47 Ma) that were emplaced in the Gumushane–Bayburt line and its vicinity. North of this line, coeval magmas show typical calc-alkaline nature and continued to develop toward further north until the middle to late Eocene. Based on the spatial and temporal variations in the magmas generated in the eastern Pontides orogenic belt, we propose a new geodynamic model to explain the tectonomagmatic evolution of these rocks and correlate the adakitic magmatism to ridge subduction and slab window process within a south-dipping subduction zone. Our model is in contrast to the previous proposals which envisage partial melting or delamination of thickened lower continental crust due to the collision in the south during the Paleocene–Eocene.  相似文献   

Secondary production of the eusirid amphipod <Emphasis Type="Italic">Pontogeneia rostrata</Emphasis> Gurjanova, 1938 (Crustacea: Peracarida) on a sandy shore in Korea     

Ok Hwan Yu  Hae-Lip Suh 《Ocean Science Journal》2011,46(3):211-217

The secondary production of the eusirid amphipod Pontogeneia rostrata Gurjanova, 1938, was examined on a sandy shore in Korea. Secondary production was estimated using a size-frequency method. The biomass structure of P. rostrata included one peak in spring, with maximum biomass occurring in April. The annual secondary production of this species was 0.57 g DW m⁻² yr⁻¹ with an annual P/B ratio of 6.97. Secondary production of P. rostrata fell within the range observed for other amphipods on intertidal sandy shores, although the production/biomass (P/B) ratio was higher than those recorded previously from the sampling site and from other tidal and estuary areas, as the number of generations increases the P/B ratio. The results showing high abundance and P/B ratios suggest that P. rostrata plays an important role in the sandy shore ecosystem as a trophic link between primary producers and higher consumers.  相似文献