Mapping hydrocarbon‐induced mineralogical alteration in the northern Tian Shan using ASTER multispectral data

Seepage from hydrocarbon reservoirs can cause a number of chemical and/or mineralogical changes in overlying rocks and soils. These surface changes can be detected by remote sensing imaging systems. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an advanced multispectral imaging system in the visible and near infrared (VNIR) to shortwave infrared (SWIR) region. Band ratios of ASTER VNIR and SWIR data to detect red bed bleaching and secondary carbonate formation induced by hydrocarbon seepage are proposed through analysis of the spectral properties of rock samples. Results show that ASTER band ratios of 2/1 and 4/8 can discriminate bleached red beds and secondary carbonate minerals due to hydrocarbon seepage in the northern Tian Shan. They are in good agreement with mineral identification using X‐ray diffraction. The ratio technique derived from ASTER data may provide a potential approach for hydrocarbon exploration in areas with sparse vegetation cover.     

Detailed paleoseismic history of the Hinagu fault zone revealed by the high-density radiocarbon dating and trenching survey across a surface rupture of the 2016 Kumamoto earthquake,Kyushu, Japan

The NE-trending Hinagu fault zone, length 81 km, is one of the major active faults in Kyushu, Japan. From north to south, it is divided into three segments based on geomorphic features and paleoseismic behavior: the Takano-Shirahata, Hinagu, and Yatsushiro Sea segments. The 2016 Kumamoto earthquake produced a 6-km-long surface rupture with a dextral strike-slip displacement on the northern part of the Takano-Shirahata segment. Surface rupture, a faint east-side-up flexure with a vertical offset of less than 8 cm, was observed near the middle of the Takano-Shirahata segment. To examine past surface-rupturing earthquakes on the Takano-Shirahata segment, including rupture frequency and timing, we conducted a paleoseismic study with boring and trenching at Yamaide. A trench across the surface rupture exposed multiple fault strands associated with multiple surface-rupturing events that deformed several strata of fine-grained sediments. By structural and stratigraphic interpretation, high-density radiocarbon dating and tephra analysis, and Bayesian modeling, we constrained the timing of seven events, Events 1–7, to 0.84–1.25, 1.31–7.06, 9.99–11.0, 10.8–12.1, 12.0–13.0, 14.2–15.1, and before 14.8 kcal BP. Slip during Events 1–6 was obviously larger than the 2016 slip. The estimated average recurrence interval was about 2596–2860 years, but the interval between Events 2 and 3 was much longer than other intervals. Moreover, the vertical throw associated with Event 2 was larger than that of other events. This implies that the Takano-Shirahata segment has a period with rare larger earthquakes and a period with frequent smaller earthquakes. Some events might have produced ruptures on both the Takano-Shirahata and the northern part of the Hinagu segments simultaneously or in a short time. The variety of recurrence intervals suggests that the seismic activity has been affected by one or both activities of the Futagawa fault zone and the Hinagu segment.     

Song Hong (Red River) delta evolution related to millennium-scale Holocene sea-level changes

The Song Hong (Red River) delta occurs on the northwest coast of the South China Sea. Its evolution in response to Holocene sea-level changes was clarified on the basis of sedimentary facies and 14 radiocarbon dates from the 40 m long Duy Tien core from the delta plain, and using previously reported geological, geomorphological, and archaeological data. The delta prograded into the drowned valley as a result of early Holocene inundation from 9 to 6 cal. kyr BP, as sea-level rise decelerated. The sea-level highstand at +2–3 m from 6 to 4 cal. kyr BP allowed widespread mangrove development on the delta plain and the formation of marine notches in the Ha Long Bay and Ninh Binh areas. During sea-level lowering after 4 cal. kyr BP, the former delta plain emerged as a marine terrace, and the delta changed into the present tide- and wave-influenced delta with accompanying beach ridges. Delta morphology, depositional pattern, and sedimentary facies are closely related to Holocene sea-level changes. In particular, falling sea level at 4 cal. kyr BP had a major impact on the evolution of the Song Hong delta, and is considered to be linked to climate changes.     

Formation and fate of sedimentary depocentres on Southeast Asia's Sunda Shelf over the past sea-level cycle and biogeographic implications

Sea-level variations are the major factor controlling sedimentation as well as the biogeographic patterns at continental margins over late Quaternary times. Fluctuations on millennial time-scales produce locally complex deposits in coasts and on shelves, associated with short-term influence on species development. This article reviews the sedimentary and biogeographic history of the tropical siliciclastic Sunda Shelf as an end-member of continental shelves regarding extreme width, an enormous sediment supply, and highest biodiversity in response to rapid sea-level fluctuations. We describe particular depositional segments as part of a genetic succession of zones from land to the deep sea based on literature data, field observations, and calculation of hydro-isostatic adjustment effects on changing relative sea level. These segments are characterized by individual sedimentary processes and deposits, and by a specific potential for material storage and re-mobilization.Long-term regressive intervals led to overall sigmoidal-promoting, extremely thick, and wide succeeding units. In contrast, rapid lateral shifts of defined depocentres over long distances took place in response to short-term sea level fluctuations. Fully isolated small-scale sediment bodies formed when sea level changed at exceptionally high rates. As a result of the high availability of organic-rich sediments, mangrove and freshwater peats formed frequently over late Quaternary times. The appearance of thick, massive and widespread peats is mainly linked to time intervals of a sea-level rise at slow rates, whilst organic matter appears much more dispersely in the sediments during episodes of rapidly changing sea level.The preservation potential of the regressive units is generally high due to highest initial sediment supply, stabilizing soil formation during exposure and rapid subsidence. Preservation of depositional elements from other periods is more exceptional and either restricted to local morphological depressions or to episodes of rapid sea level change. Besides complex channel incision, an overall lowering of the sediment surface related to erosion, as deep as 20 m or more, over wide areas took place mainly during sea level lowering. The final export of shelf material is documented by enormous mass-wasting packages on the associated continental slope.From a palaeogeographic perspective, the rapid formation or disappearance of special habitat zones, such as mangrove fringes and extended mud flats, led to species establishment or truncation in distribution. In addition, the opening or closure of ocean passages, as narrow bridges allowing limited species crossing or as fully colonized corridors, had severe impact on eco-fragmentation and the expansion or contraction of species. Independent of such particular conditions, sea-level changes have been too rapid over the past climatic cycle to allow full regeneration and mature development of coast-related ecosystems.     

Cyclone activity associated with the interannual seesaw oscillation of summer precipitation over northern Eurasia

This study describes surface cyclone activity associated with the interannual variability in summer precipitation in northern Eurasia and how that activity may be connected to other climate signals. An east–west seesaw oscillation of precipitation across Siberia is the primary mode of interannual variability in the summer hydrological cycle over northern Eurasia. This variation occurs at sub-decadal timescales of about 6–8 years. The spatial characteristics of cyclone frequency and cyclone tracks at the two poles in variability [eastern Siberia (ES)-wet–western Siberia (WS)-dry and WS-wet–ES-dry] were examined, and temporal variability in regional cyclone frequency was compared to basin-scale precipitation variability. The analysis period was from 1973 to 2002, when the precipitation variability signal was predominant.Cyclone behavior suggested that the regions of enhanced (reduced) cyclone activity coincided with regions of increased (decreased) precipitation in each phase of the oscillation. Such behavior reflects the zonal displacement of the track of frequent storm activity that accompanies the changes in precipitation. Comparisons of the temporal characteristics confirmed the importance of regional cyclone frequency on precipitation variability in both eastern and western Siberia. Low-frequency changes in regional cyclone activity may produce the precipitation oscillation. We used various climate signals to explore connections between regional precipitation and cyclone activity in Siberia. Results suggest that the North Atlantic Oscillation (NAO) from the preceding winter is significantly and negatively correlated with summer surface cyclone frequency and precipitation over western Siberia. Enhanced (reduced) summer cyclone activity and precipitation in western Siberia follows low- (high-) winter NAO. However, the physical mechanisms linking summer cyclone activity and precipitation over western Siberia with the preceding climate conditions associated with the winter NAO remain unclear.     

Tide‐modulated hyperpycnal flows off the Huanghe (Yellow River) mouth,China

Few hyperpycnal flows have ever been observed in marine environments although they are believed to play a critical role in sediment dispersal within estuarine and deltaic depositional systems. The paper describes hyperpycnal flows observed in situ off the Huanghe (Yellow River) mouth, their relationship to tidal cycles, and the mechanisms that drive them. Simultaneous observations at six mooring stations during a cruise off the Huanghe mouth in the flood season of 1995 suggest that hyperpycnal flows observed at the river mouth are initiated by high concentrations of sediment input from river and modulated by tides. Hyperpycnal flows started near the end of ebb tides, when near‐bottom suspended sediment concentration (SSC) increased rapidly and salinity decreased drastically (an inverse salt wedge). The median grain size of suspended particles within the hyperpycnal layer increased, causing strong stratification of the suspended sediments in the water column. Towards the end of flood tides, the hyperpycnal flow attenuated due to frictions at the upper and lower boundaries of the flow and tidal mixing, which collapsed the stratification of the water column. Both sediment concentration and median grain size of suspended particles within the bottom layer significantly decreased. The coarser sediment particles were deposited and the hyperpycnal flows stopped. The intra‐tidal behaviors of hyperpycnal flows are closely associated with the variations of SSC, salinity, and stratification of the water column. As nearly 90% of riverine sediment is delivered to the sea during the flood seasons when hyperpycnal flows are active, hyperpycnal flows at the Huanghe mouth and the river's high sediment loads have caused rapid accretion of the Huanghe delta. Copyright © 2010 John Wiley & Sons, Ltd.     

Verification of system identification utilizing shaking table tests of a full‐scale 4‐story steel building

This paper verifies the feasibility of the proposed system identification methods by utilizing shaking table tests of a full‐scale four‐story steel building at E‐Defense in Japan. The natural frequencies, damping ratios and modal shapes are evaluated by single‐input‐four‐output ARX models. These modal parameters are prepared to identify the mass, damping and stiffness matrices when the objective structure is modelled as a four degrees of freedom (4DOF) linear shear building in each horizontal direction. The nonlinearity in stiffness is expressed as a Bouc–Wen hysteretic system when it is modelled as a 4DOF nonlinear shear building. The identified hysteretic curves of all stories are compared to the corresponding experimental results. The simple damage detection is implemented using single‐input‐single‐output ARX models, which require only two measurements in each horizontal direction. The modal parameters are equivalent‐linearly evaluated by the recursive Least Squares Method with a forgetting factor. When the structure is damaged, its natural frequencies decrease, and the corresponding damping ratios increase. The fluctuation of the identified modal properties is the indirect information for damage detection of the structure. Copyright © 2015 John Wiley & Sons, Ltd.     

Grain size records reveal variability of the East Asian Winter Monsoon since the Middle Holocene in the Central Yellow Sea mud area,China

Three cores(ZY-1,ZY-2 and ZY-3) retrieved from the Central Yellow Sea mud(CYSM) were analyzed in sensitive grain size and AMS 14 C dating to reconstruct the history of the East Asian Winter Monsoon(EAWM) since the Middle Holocene in the study area.The results show that these data provide a continuous history of the EAWM over the past 7.2 ka and that the EAWM can be divided into three periods:strong and highly fluctuating during 7.2-4.2 ka BP;moderate and relatively stable during 4.2-1.8 ka BP;and weakened during 1.8-0 ka BP.Compared with the East Asian Summer Monsoon(EASM) recorded in the previous studies,the evolutionary history of the EAWM broadly follows the orbital-derived winter insolation with a similar long-term step-decreased trend as the EASM.At the centennial scale,however,the EAWM intensified events correlate well with the EASM weakened events and the North Atlantic climatic variations(Bond events 0 to 5) within the dating error,most likely forced by the reduction of solar irradiance through changes in the oceanic-atmospheric circulation patterns.     

An active mass damper designed using ARX models of a building structure

This study proposes a new design method for an active mass damper (AMD) that is based on auto‐regressive exogenous models of a building structure. The proposed method uses the results of system identification in the field of active structural control. The uncontrolled structure is identified as auto‐regressive exogenous models via measurements under earthquake excitation and forced vibration. These models are linked with an equation of motion for the AMD to introduce a state equation and output equation for the AMD–structure interaction system in the discrete‐time space; the equations apply modern control theories to the AMD design. In the numerical applications of a 10‐degree‐of‐freedom building structure, linear quadratic regulator control is used to understand the fundamental characteristics of the proposed design procedure. The feedback control law requires the AMD's acceleration, velocity and stroke; the structure's acceleration; and the ground acceleration as vibration measurements. The numerical examples confirm the high applicability and control effectiveness of the proposed method. One remarkable advantage of the proposed method is that an equation of motion for the structure becomes unnecessary for designing controllers. Copyright © 2016 John Wiley & Sons, Ltd.     

帕米尔东北缘ASTER多光谱热红外遥感数据的岩性信息提取

搭载于美国航空航天局（NASA）Tera卫星上的ASTER传感器具有从太空测量来自地球表面的多光谱热红外（TIR）辐射的能力。基于地球表面典型岩石类型的热红外光谱特征分析，我们建立了几种探测硅质岩、碳酸岩及硅酸盐岩中全岩SiO2含量的指数，我们将这些指数应用于帕米尔东北缘地区的ASTER多光谱热红外图像数据，并将遥感解译分析结果与该区已发表的地质资料和野外调查结果进行比较。结果表明，ASTER热红外遥感方法具有很大的应用潜力：它可以有效地提供整个帕米尔地区的主要地质信息。这是常规的地质调查方法无法完成的，因为该区的野外地质调查受到自然地理条件等因素的限制。