• Earthquakes and Structures
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• v.11 no.3
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• pp.517-538
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• 2016

This paper presents a probabilistic fragility analysis for two groups of bridges: simply supported and integral bridges. Comparisons are based on the seismic fragility of the bridges subjected to accelerograms of two seismic sources. Three-dimensional finite-element models of the bridges were created for each set of bridge samples, considering the nonlinear behaviour of critical bridge components. When the seismic hazard in the site is controlled by a few seismic sources, it is important to quantify separately the contribution of each fault to the structure vulnerability. In this study, seismic records come from earthquakes that originated in strike-slip and reverse faulting mechanisms. The influence of the earthquake mechanism on the seismic vulnerability of the bridges was analysed by considering the displacement ductility of the piers. An in-depth parametric study was conducted to evaluate the sensitivity of the bridges' seismic responses to variations of structural parameters. The analysis showed that uncertainties related to the presence of lap splices in columns and superstructure type in terms of integral or simply supported spans should be considered in the fragility analysis of the bridge system. Finally, the fragility curves determine the conditional probabilities that a specific structural demand will reach or exceed the structural capacity by considering peak ground acceleration (PGA) and acceleration spectrum intensity (ASI). The results also show that the simply supported bridges perform consistently better from a seismic perspective than integral bridges and focal mechanism of the earthquakes plays an important role in the seismic fragility analysis of highway bridges.

• Economic and Environmental Geology
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• v.32 no.4
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• pp.365-371
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• 1999

Ture diplacement of a fault monement is calculated from the displacement of the index plane such as bedding on an outcrop surface. The input parameters are the orientations of the index, fault, and outcrop planes. It is also necessary to input the orientation of fault striation and the offset distance of the index plane on the outcrop surface. The distances of the total, strike, horizontal and dip slip components of the fault movement are calculated from the input parameters. Hwang(1998) conducted a simlar calculation using trigonoment method. To apply the previous method, the offset distance of the index plane must be measured on a vertical outcrop surface. The calculation method of this study accepts the offset distence of index plane on an outcrop plane of any orientation. Calculation results from both method are indentical, regardless of the simplicity of the new method.

• Geomechanics and Engineering
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• v.30 no.4
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• pp.353-362
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• 2022

The seismic failure-prone region in Istanbul has been examined in terms of the segmented pipelines. Although some researchers have suggested that this territory should be left as a green land, many people continue to live in this area. This region is about 9-10 km away from the North Anatolian Fault Line. This fault zone is an active right-lateral strike-slip fault line in Turkey and an earthquake with a magnitude of 7.0-7.5 is expected in the Marmara Sea. Therefore, superstructures and infrastructures are under both land sliding risks and seismic risks in this area. Because there are not any pipeline-fault line intersection points in the region, in this study, it has been focused on the behaviors of the segmented (sewage or stormwater) pipelines subject to earthquake-induced permanent ground deformation and seismic wave propagation. Based on the elastic beam theory some necessary analyses have been carried out and obtained results of this approximation have been examined.

• The Journal of Engineering Geology
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• v.9 no.1
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• pp.59-68
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• 1999

To clarify the geological structure of Yangsan fault around Sangchon-ri in the southern part of Kyungsang Basin the resistivity (dipole-dipole profiling) and VLF surveys carried out on the four profiles, crossing the inferred trace of the fault. The resistivity contrast across the fault is clearly shown on the profiles: higher resistivity and lower resistivity on the east and west, respectively. It is most likely from the uplift of the granitic bedrock on the east park due to the strike-fault raulting with vertical movement. The zero-crossing points of VLF anomalies, associated with near-surface fracture zone, are found to well correlate with the resistivity boundaries from the dipole-dipole profiling. Consequently, southern segment of Yangsan fault (at Sangchon-ri area) is interpreted to be vertically developed strike-slip fault with a difference more than 10m depth of basement rock at both sides.

• Economic and Environmental Geology
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• v.27 no.1
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• pp.65-80
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• 1994

The Tertiary $Ch{\check{o}}ngja$ basin is located in the southeastern coastal area of the Korean Peninsula. It is a lozenge shaped fault-bounded basin with circa $5{\times}5km$ areal extent, isolated from other Tertiary basins by the Cretaceous Ulsan Formation in-between. The northwestern boundary of the basin is a domino/listric type normal fault trending $N30^{\circ}E$, whereas its southwestern boundary is a dextral strike-slip fault (trending $N20^{\circ}W$) with a lateral offset of more than 1 km. The basin is bounded by the East Sea on the eastern margin. Basin-fills consist of extrusive volcanic rock (Tangsa Andesites) of Early Miocene (16~22 Ma in radiometric age), unconsolidated fluviatile conglomerate (Kangdong Formation) and shallow brackish-water sandstone ($Sinhy{\check{o}}n$ Formation). The latter yields abundant Vicarya-Anadara molluscan fossils of early Middle Miocene age. The Tertiary strata become younger toward the northwestern boundary-fault of the basin, showing a zonal distribution pattern parallel to the fault: the younger sedimentary formations occupy a narrow zone of 2 km width along the northwestern boundary-fault, whereas the older Tangsa Andesites underlie them unconformably in the eastern and southeastern portions of the basin. The strata in the basin, including the Tangsa Andesites, are tilted (about $20^{\circ}$) toward the northwestern boundary-fault Sedimentary strata thicken toward the boundary-fault, forming a wedge shaped half-graben structure. A number of small-scale syndepositional normal growth faults and graben structures are observed in the sedimentary strata. These extensional structures have the same trend as the normal northwestern boundary-fault which we interpret as a pull-apart detachment fault. These characteristics imply persistent extension during the basin evolution, caused by a NW-SE directed tensional force. The $Ch{\check{o}}ngja$ basin is, thus, a kind of syndepositional tectonic basin evolved in a strike-slip (pull-apart) regime. The latter was caused by a dextral simple shear associated with the NNW-SSE opening of the East Sea. In view of the fact that the normal growth faults do not cut through the uppermost portion of the youngest $Sinhy{\check{o}}n$ Formation, it is inferred that the tensional force came to be inactive in the early Middle Miocene. This is coincident in timing with the termination of the East Sea opening (15 Ma).

• Geomechanics and Engineering
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• v.34 no.4
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• pp.409-424
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• 2023

Response of the pipeline crossing fault is considered as the large strain problem. Proper estimation of the pipeline response plays important role in mitigation studies. In this study, an advanced continuum modeling including material non-linearity in large strain deformations, hardening/softening soil behavior and soil-pipeline interaction is applied. Through the application of a fully nonlinear analysis based on an explicit finite difference method, the mechanics of the pipeline behavior and its interaction with soil under large strains is presented in more detail. To make the results useful in oil and gas engineering works, a continuous pipeline of two steel grades buried in two clayey soil types with four different crossing angles of 30°, 45°, 70° and 90° with respect to the pipeline axis have been considered. The results are presented as the fault movement corresponding to different damage limit states. It was seen that the maximum affected pipeline length is about 20 meters for the studied conditions. Also, the affected length around the fault cutting plane is asymmetric with about 35% and 65% at the fault moving and stationary block, respectively. Local buckling is the dominant damage state for greater crossing angle of 90° with the fault displacement varying from 0.4 m to 0.55 m. While the tensile strain limit is the main damage state at the crossing angles of 70° and 45°, the cross-sectional flattening limit becomes the main damage state at the smaller 30° crossing angles. Compared to the stiff clayey soil, the fault movement resulting 3% tensile strain limit reach up to 40% in soft clayey soil. Also, it was seen that the effect of the pipeline internal pressure reaches up to about 40% compared to non-pressurized condition for some cases.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.4
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• pp.41-52
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• 1998

The Dongnae Fault in the southeastern part of the Korean Peninsular is not a single fault but a complex fault zone composed of numerous minor faults. In order to deduce the paleostress tensor evolving the Dongnae Fault, we measured 329 faults in outcrops around the fault zone and analyzed the geometries of them. Most of them are steeply dipping(>65˚) and fall into three groups striking N10E, N30E and N70E. More than one half of them show the rakes less than 30˚ Paleostress tensor analysis using the collected fault data has been conducted with the Angelier's direct inversion method and the Choi's method. As result, four different principal paleostress axes each of which subtends an independent tectonic event are found. They are; (1) NNE-SSW compression and ESE-WNW extension (Event I), (2) NNE-SSW extension (Event II), (3) ESE-WNW extension (Event III) and (4) ENE-WSW compression and NNW-SSE extension (Event IV) in chronology. Therefore, the tectonic movement around the Dongnae Fault was firstly governed by strike-slip faulting related to Event I. Afterward, normal faults were formed by Event II and Event III. Finally, the dextral strike-slip faults along the major trace of the Dongnae Fault were formed in NNE direction related to Event IV.

• The Journal of the Petrological Society of Korea
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• v.11 no.3_4
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• pp.250-258
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• 2002

The wavy extinction of quartz can be used as a standard indicator showing the degree of rock deformation. To determine the degree of rock deformation, the intensity of wavy extinction (IWE) of quartz was measured using petroggraphic microscope, digital camera, and NIH image. In this study, this method was applied to the Cheongsan porphyritic granite, Cheongsan two mica granite, and Baekrok granite to investigate the deformation intensity of Cheongsan area. NIH Image data show a high-grade deformation in the vicinity of the strike-slip fault (between Cheongsan granite and Baekrok granite) and the unconformity (between Cheongsan granite and Youngdong basin). Thus, the main deformation in these areas is most likely to be concentrated on the faults that generate Yeongdong basin and the strike slip faults between Cheongsan granite and Baekrok granite.

• Journal of the Korean earth science society
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• v.27 no.3
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• pp.341-347
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• 2006

Focal mechanisms were analyzed for the seven earthquakes which occurred in the southwestern part of the Korea Peninsula from 2001 to 2005. Grid searches are performed to fit distributions of P-wave first-motion polarities and SH/P amplitude ratios for each event. The focal mechanism solutions imply that most of the events have strike-slip sense including partially thrust component. The compressional axes of the solutions are predominantly ENE-WSW or NE-SW indirections. This result is similar to the directions of the principal compressional axes for major earthquakes occurred around the Korea Peninsula.

• Economic and Environmental Geology
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• v.28 no.6
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• pp.579-585
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• 1995

The Samkwang mine is Cretaceous gold-silver-bearing deposits located in the western part of the Ogcheon belt The ore deposits have been emplaced within granite gneiss of the Precambrian age. The Au-Ag deposits are hydrothermal-vein type, characterized by arsenic-, gold- and silver-bearing sulphides, in addition to the principal ore-forming sulphides arsenopyrite, galena, sphalerite, chalcopyrite, pyrite and pyrrhotite. Their proven reserves are 355,000 MT, and grades are 8.4 g Au/t and 13.6 g Ag/t. On the basis of their structural characters, the Au-Ag-bearing quartz veins are classified into three types of ore veins; (1) The Main vein shows $N40^{\circ}-80^{\circ}E$ strike and $55^{\circ}-90^{\circ}SE$ dip, (2) the Sangban vein shows E-W strike and $30^{\circ}-40^{\circ}S$ dip, and (3) the Gukseong vein has $N25^{\circ}-40^{\circ}W$strike and $65^{\circ}-80^{\circ}SW$ dip. The emplacements of the ore veins are closely related to the minimum stress axis $({\sigma}_3)$ during the strike-slip movement of the study area. The ore-bearing veins filled with extension fractures during strike-slip movements were sequentially emplaced as follows: I) When ${\sigma}_1$ operates obliquely to NE-series discontinous surface, the Main fault zone $(F_1)$ developes. 2) During the same time, extension fractures ($T_1$ Gukseong veins) take place. 3) When the fault progress continuously, the existing $T_1$, may be high angle and $T_2$ (Daehung vein) developes continuously. 4) When ${\sigma}_1$ changes to sinistral sense, $T_3$ (basic dyke) occurs. 5) When a reverse fault becomes active, the Sangban vein is branched from the Guksabong vein.