Recurrent events on a Quaternary fault recorded in the mineralogy and micromorphology of a weathering profile, Yangsan Fault System, Korea

Recurrence characteristics of a Quaternary fault are generally investigated on the basis of field properties that are rapidly degraded by chemical weathering and erosion in warm humid climates. Here we show that in intense weathering environments, mineralogical and micromorphological investigations are valuable in paleoseismological reconstruction. A weathering profile developed in Late Quaternary marine terrace deposits along the southeastern coast of the Korean Peninsula was disturbed by tectonic movement that appears to be a simple one-time reverse faulting event based on field observations. A comparative analysis of the mineralogy, micromorphology, and chemistry of the weathering profile and fault gouge, however, reveals that both the microfissures in the deformed weathering profile and larger void spaces along the fault plane were filled with multi-stage accumulations of illuvial clay and silt minerals of detrital origin, suggesting a repetition of fissuring and subsequent sealing in the weathering profile as it underwent continuous mineralogical transformation and particle translocation. We reconstruct a sequence of multiple faulting events unrecognized in previous field surveys, which requires revision of the view that the Korean Peninsula was tectonically stable, during the Late Quaternary.     

An Experimental Performance Evaluation of Spatio-Temporal Join Strategies

Many applications capture, or make use of, spatial data that changes over time. This requirement for effective and efficient spatio‐temporal data management has given rise to a range of research activities relating to spatio‐temporal data management. Such work has sought to understand, for example, the requirements of different categories of application, and the modelling facilities that are most effective for these applications. However, at present, there are few systems with fully integrated support for spatio‐temporal data, and thus developers must often construct custom solutions for their applications. Developers of both bespoke solutions and of generic spatio‐temporal platforms will often need to support the fusion of large spatio‐temporal data sets. Supporting such requests in a database setting involves the use of join operations with both spatial and temporal conditions – spatio‐temporal joins. However, there has been little work to date on spatio‐temporal join algorithms or their evaluation. This paper presents an evaluation of several approaches to the implementation of spatio‐temporal joins that build upon widely available indexing techniques. The evaluation explores how several algorithms perform for databases with different spatial and temporal characteristics, with a view to helping developers of generic infrastructures or custom solutions in the selection and development of appropriate spatio‐temporal join strategies.     

The effect of earthquake duration on the damage of structures

This paper presents a theoretical analysis of the effect of duration on the damage of structures subjected to earthquakes. The earthquake excitation is modelled by a non-stationary random process whose response spectrum is probabilistically consistent with a design response spectrum specified independently of the duration. Damage is assumed to accumulate with the cyclic application of large strains in the structural members. Two types of structure are examined: one representative of a steel structure and the other reprsentative of a reinforced concrete structure. The level of expected damage is found to be a strong function of both the ductility of the response and the duration of the excitation. Results are presented for systems with linear stiffness and a particular form of softening behaviour.     

Spatial and temporal variations of spatial population accessibility to public hospitals: a case study of rural–urban comparison

Quantification and assessment of nationwide population access to health-care services is a critical undertaking for improving population health and optimizing the performance of national health systems. Rural–urban unbalance of population access to health-care services is widely involved in most of the nations. This unbalance is also potentially affected by varied weather and road conditions. This study investigates the rural and urban performances of public health system by quantifying the spatiotemporal variations of accessibility and assessing the impacts of potential factors. Australian health-care system is used as a case study for the rural–urban comparison of population accessibility. A nationwide travel time-based modified kernel density two-step floating catchment area (MKD2SFCA) model is utilized to compute accessibility of travel time within 30, 60, 120, and 240 min to all public hospitals, hospitals that provide emergency care, and hospitals that provide surgery service, respectively. Results show that accessibility is varied both temporally and spatially, and the rural–urban unbalance is distinct for different types of hospitals. In Australia, from the perspective of spatial distributions of health-care resources, spatial accessibility to all public hospitals in remote and very remote areas is not lower (and may even higher) than that in major cities, but the accessibility to hospitals that provide emergency and surgery services is much higher in major cities than other areas. From the angle of temporal variation of accessibility to public hospitals, reduction of traffic speed is 1.00–3.57% due to precipitation and heavy rain, but it leads to 18–23% and 31–50% of reduction of accessibility in hot-spot and cold-spot regions, respectively, and the impact is severe in New South Wales, Queensland, and Northern Territory during wet seasons. Spatiotemporal analysis for the variations of accessibility can provide quantitative and accurate evidence for geographically local and dynamic strategies of allocation decision-making of medical resources and optimizing health-care systems both locally and nationally.     

Field application of freezing technology for social infrastructures

There are numerous methods to prevent seepage flow and ground improvement methodologies such as cement grouting, sheet piling, and the membrane method. In this paper, we present case histories of freezing technology applications in the construction of a deep tunnel sewerage system, undersea highway tunnel, and liquefied natural gas tank. Heaving pressure measurements for various soil types around a liquefied natural tank are compared with existing data. In this paper, we present temperature variations at the bottom and side of a liquefied natural gas tank. Our findings show that ground-freezing technology is very effective in controlling ground water infiltration into underground structures as well providing soil reinforcement in the soft ground.     

Development of the Operational Oceanographic System of Korea

Ocean Science Journal - The Korea Operational Oceanographic System (KOOS) was developed at the Korea Institute of Ocean Science and Technology (KIOST) to produce real-time forecasting and...     

Northern Barbados accretionary prism: Structure,deformation, and fluid flow interpreted from 3D seismic and well‐log data

We reanalyzed 3D seismic reflection and logging‐while‐drilling data from the toe of the northern Barbados accretionary prism to interpret structure, deformation, and fluid flow related to subduction processes. The seafloor amplitude and coherence reveal an abrupt change in the thrust orientation from NNE at the thrust front and north and NNW about 5 km west of the thrust front. These thrust sets are separated by a triangular‐shaped quiet area, which may represent a zone of low strength. The northeast‐trending band of strong negative amplitude and high coherence in the décollement, known to be an interval of arrested consolidation, overlaps the quiet area, suggesting that the arrested consolidation may be related to the lack of thrust imbrication, and thus, vertical drainage for fluid in the accretionary prism. Fractal analysis of the décollement and top of the subducting oceanic basement indicates that the relief of the décollement correlates with the topography of the oceanic basement. Differential compaction of the underthrust sediment overlying the rugged oceanic basement, together with the basement faults that penetrate into the décollement probably caused relief or even faulting in the décollement.     

Semi-auto horizon tracking guided by strata histograms generated with transdimensional Markov-chain Monte Carlo

Although horizon interpretation is a routine task for building reservoir models and accurately estimating hydrocarbon production volumes, it is a labour-intensive and protracted process. Hence, many scientists have worked to improve the horizon interpretation efficiency via auto-picking algorithms. Nevertheless, the implementation of a classic auto-tracking method becomes challenging when addressing reflections with weak and discontinuous signals, which are associated with complicated structures. As an alternative, we propose a workflow consisting of two steps: (1) the computation of strata histograms using transdimensional Markov-chain Monte Carlo and (2) horizon auto-tracking using waveform-based auto-tracking guided by those strata histograms. These strata histograms generate signals that are vertically sharper and more laterally continuous than original seismic signals; therefore, the proposed workflow supports the propagation of waveform-based auto-picking without terminating against complicated geological structures. We demonstrate the performance of the novel horizon auto-tracking workflow through seismic data acquired from the Gulf of Mexico, and the Markov-chain Monte Carlo inversion results are validated using log data. The auto-tracked results show that the proposed method can successfully expand horizon seed points even though the seismic signal continuity is relatively low around salt diapirs and large-scale faults.