Double-difference tomography of P- and S-wave velocity structure beneath the western part of Java,Indonesia     

Shindy Rosalia  Sri Widiyantoro  Andri Dian Nugraha  Pepen Supendi 《地震科学（英文版）》2019,32(1):12-25

West Java in the western part of the Sunda Arc has a relatively high seismicity due to subduction activity and faults. In this study, double-difference tomography was used to obtain the 3D velocity tomograms of P and S waves beneath the western part of Java. To infer the geometry of the structure beneath the study area, precise earthquake hypocenter determination was first performed before tomographic imaging. For this, earthquake waveform data were extracted from the regional Meteorological, Climatological, Geophysical Agency (BMKG) network of Indonesia from South Sumatra to Central Java. The P and S arrival times for about 1,000 events in the period April 2009 to July 2016 were selected, the key features being events of magnitude > 3, azimuthal gap < 210° and number of phases > 8. A nonlinear method using the oct-tree sampling algorithm from the NonLinLoc program was employed to determine the earthquake hypocenters. The hypocenter locations were then relocated using double-difference tomography (tomoDD). A significant reduction of travel-time (root mean square basis) and a better clustering of earthquakes were achieved which correlated well with the geological structure in West Java. Double-difference tomography was found to give a clear velocity structure, especially beneath the volcanic arc area, i.e., under Mt Anak Krakatau, Mt Salak and the mountains complex in the southern part of West Java. Low velocity anomalies for the P and S waves as well as the v_P/v_S ratio below the volcanoes indicated possible partial melting of the upper mantle which ascended from the subducted slab beneath the volcanic arc.  相似文献   

The evolution of brittle and ductile structures at the surface of a partly debris-covered,rapidly thinning and slowly moving glacier in 1998–2012 (Pasterze Glacier,Austria)     

Andreas Kellerer-Pirklbauer  Bernd Kulmer 《地球表面变化过程与地形》2019,44(5):1034-1049

Many glaciers in alpine regions are currently rapidly receding and thinning at historically unobserved rates causing changes in the velocity field and in normal and shear stresses affecting the surface expression of structures within the ice. We studied the distribution of brittle and ductile structures at the surface of Pasterze Glacier during a 14-year period by analysing orthophotos and digital elevation models of five stages (1998, 2003, 2006, 2009 and 2012). A structural glaciological mapping key was applied. Normal faults, strike-slip faults, en échelon structures (systematic stepping of fractures), thrust faults, and band ogives were distinguished. Results indicate substantial deceleration and glacier thinning in 1998–2012. Glacier thinning was not homogenous over time related to the uneven distribution of supraglacial debris causing differential ablation or the selective ablation effects of subglacial water channels. Peculiar supraglacial features observed are circular collapse structures with concentric crevasses which form when the ice between the surface and the roof of water channels decreases. The total length of brittle structures increased from 38.4 km to 56.9 km whereas the extent of the glacier tongue decreased by 25%. The fracture density doubled from 0.009 to 0.018 m/m². Areas of the glacier tongue which were up to 100 m away from the nearest brittle structure increased by 16%. The visual appearance of thrust faults shifted upglacier due to decreasing glacier velocity causing horizontal shortening or due to exhumation of faults that did not previously extend to the surface. A large number of brittle structures are progressively independent from glacier motion. Our study suggests that glacier tongues which are in a state of rapid decay and thinning are prone to fracturing due to normal fault formation and glacier disintegration. Water further increases ablation rates substantially if rather large amounts drain through supra-, en- or subglacial water channels. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

招平断裂带中段深部结构构造——来自地震剖面的证据   总被引：1，自引：0，他引：1       下载免费PDF全文

单伟  于学峰  李洪奎  郭宝奎  耿科  李大鹏  禚传源 《山东国土资源》2018,34(5)

玲珑花岗岩岩基东侧的招平断裂带是胶西北矿集区的主要控矿构造之一。布设于招平断裂带中段大尹格庄矿区的地震剖面,揭示了招平断裂带中段深部的结构构造特征,地震剖面显示,玲珑岩基内部有多个类似"拱弧构造"的岩浆侵入形成的弧形界面,由此推测存在2~3期的岩浆活动。剖面显示了3期构造组合样式,第1期为以招平断裂带和宋家河断裂为组合倾向SE的铲式断裂,底部似汇入统一的构造滑脱带;第2期为倾向NW的错断了招平断裂带的反倾伸展断裂;第3期为NE向延伸以花状构造为特征的走滑断裂。前两期反映构造发育处于伸展环境,第3期显示为左行走滑。招平断裂带深部延伸存在分支复合现象,形成由2个主裂面夹持的透镜状岩片。地震反射剖面数据的获得对深刻理解该区域中生代岩浆构造演化过程和深部找矿具有重要的借鉴意义。  相似文献   

Estuarine biofilm patterns: Modern analogues for Precambrian self-organization     

Roeland C. van de Vijsel  Jim van Belzen  Tjeerd J. Bouma  Daphne van der Wal  Valentina Cusseddu  Sam J. Purkis  Max Rietkerk  Johan van de Koppel 《地球表面变化过程与地形》2020,45(5):1141-1154

This field and laboratory study examines whether regularly patterned biofilms on present-day intertidal flats are equivalent to microbially induced bedforms found in geological records dating back to the onset of life on Earth. Algal mats of filamentous Vaucheria species, functionally similar to microbial biofilms, cover the topographic highs of regularly spaced ridge–runnel bedforms. As regular patterning is typically associated with self-organization processes, indicators of self-organization are tested and found to support this hypothesis. The measurements suggest that biofilm-induced sediment trapping and biostabilization enhance bedform relief, strength and multi-year persistence. This demonstrates the importance of primitive organisms for sedimentary landscape development. Algal-covered ridges consist of wavy-crinkly laminated sedimentary deposits that resemble the layered structure of fossil stromatolites and microbially induced sedimentary structures. In addition to layering, both the morphological pattern and the suggested formation mechanism of the recent bedforms are strikingly similar to microbialite strata found in rock records from the Precambrian onwards. This implies that self-organization was an important morphological process in times when biofilms were the predominant sessile ecosystem. These findings furthermore emphasize that self-organization dynamics, such as critical transitions invoking ecosystem emergence or collapse, might have been captured in fossil microbialites, influencing their laminae. This notion may be important for paleoenvironmental reconstructions based on such strata. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

基于拉格朗日拟序结构的黑潮区域海流运输结构提取和分析     

田丰林  任一丹  何遒  陈戈 《海洋学报》2020,42(5):12-21

海流的拉格朗日运动对于研究物质输送有着重要意义，拉格朗日拟序结构(LCSs)作为研究海流结构的新型方法，相比于传统欧拉方法更为客观。本文提出了一种新的计算LCSs束的方法，基于25年的平均速度场，利用变分方法计算得到黑潮区域的气候态LCSs，并通过简化合并的方法得到了气候态LCSs束，该LCSs束能够突出地显示出海流特性和运输模式，其代表的平均拉格朗日环流有很强的约束作用，且具有鲁棒性。最终我们获得了气候态下12个月份的流场结构图，揭示了月周期性拉格朗日环流规律。本文还利用虚拟粒子输运、多年浮标轨迹以及气候态温盐异常3种方法进行了验证，与拉格朗日运输模式相吻合，证明了海流拉格朗日拟序结构的准确性和可靠性。  相似文献   

海上构筑物用海存在的问题及管理政策建议          下载免费PDF全文

李珊  徐伟  刘淑芬 《海洋开发与管理》2020,37(6):108-114

随着社会经济的发展和海洋资源开发利用水平的提高，海上人工构筑物呈现种类、数量和规模都迅速增长的态势。但目前我国大部分海上构筑物尚未纳入统一的管理体系，导致管理权限不清和管理环节缺位。文章分析我国海上构筑物管理的现状和存在的问题，从海洋管理实践出发，对海上构筑物管理进行有益探索，提出在协调众多涉海部门的基础上，从审批、登记、竣工验收、弃置管理、事中事后监管等方面，解决最紧迫的管理需求，先易后难地完善海上构筑物管理的缺位环节，逐步建立和完善海上构筑物管理制度体系，更好地服务于海洋经济建设。  相似文献   

Lifecycle cost optimization of tuned mass dampers for the seismic improvement of inelastic structures     

Emiliano Matta 《地震工程与结构动力学》2018,47(3):714-737

The seismic performance of tuned mass dampers (TMDs) on structures undergoing inelastic deformations may largely depend on the ground motion intensity. By estimating the impact of each seismic intensity on the overall cost of future seismic damages, lifecycle cost (LCC) proves a rational metric for evaluating the benefits of TMDs on inelastic structures. However, no incorporation of this metric into an optimization framework is reported yet. This paper presents a methodology for the LCC‐optimal design of TMDs on inelastic structures, which minimizes the total seismic LCC of the combined building‐TMD system. Its distinctive features are the assumption of a mass‐proportional TMD cost model, the adoption of an iterative suboptimization procedure, and the initialization of the TMD frequency and damping ratios according to a conventional linear TMD design technique. The methodology is applied to the seismic improvement of the SAC‐LA benchmark buildings, taken as representative of standard steel moment‐resisting frame office buildings in LA, California. Results show that, despite their limited performance at the highest intensity levels, LCC‐optimal TMDs considerably reduce the total LCC, to an extent that depends on both the building vulnerability and the TMD unit cost. They systematically present large mass ratios (around 10%) and frequency and damping ratios close to their respective linearly designed optima. Simulations reveal the effectiveness of the proposed design methodology and the importance of adopting a nonlinear model to correctly evaluate the cost‐effectiveness of TMDs on ordinary structures in highly seismic areas.  相似文献   

Wave run-up on bermed coastal structures     

《Applied Ocean Research》2019

Reliable estimation of wave run-up is required for the effective and efficient design of coastal structures when flooding or wave overtopping volumes are an important consideration in the design process. In this study, a unified formula for the wave run-up on bermed structures has been developed using collected and existing data. As data on berm breakwaters was highly limited, physical model tests were conducted and the run-up was measured. Conventional governing parameters and influencing factors were then used to predict the dimensionless run-up level with 2% exceedance probability. The developed formula includes the effect of water depth which is required in understanding the influence of sea level rise and consequent changes of wave height to water depth ratio on the future hydraulic performance of the structures. The accuracy measures such as RMSE and Bias indicated that the developed formula is more accurate than the existing formulas. Additionally, the new formula was validated using field measurements and its superiority was observed when compared to the existing prediction formulas. Finally, the new design formula incorporating the partial safety factor was introduced as a design tool for engineers.  相似文献   

地下结构抗震设计的改进等效反应加速度法     

禹海涛  张正伟  李攀 《岩土力学》2020,41(7):2401-2410

对地下结构横向抗震分析中的等效反应加速度法进行综合分析。结合算例，以动力时程法为基准，全面评价了等效反应加速度法的适用性；进而深入分析其误差来源，并做针对性改进优化，通过引入动力响应调整系数β，提出了一种改进等效反应加速度法；结合算例分析，评价了改进等效反应加速度法对不同工况的适用性。结果表明：等效反应加速度法计算所得结构内力及变形均偏小；且计算精度随地层剪切波速的增大整体呈上升趋势，但几乎不受结构埋深的影响；同时，明确了等效反应加速度法的误差源自于其忽略了地下结构对其周围土体动力响应的干扰作用，改进优化后提出了改进等效反应加速度法；相比现有等效反应加速度法，改进等效反应加速度法具有更广泛的适用性及更优的计算精度，可为地下结构抗震设计和分析提供新的计算方法。  相似文献   

Analytical solution of seismic response of base-isolated structure with supplemental inerter     

Kun Ye  Shuai Shu  Liang Hu  Hongping Zhu 《地震工程与结构动力学》2019,48(9):1083-1090

Closed-form solutions are derived for the modal characteristics and seismic response of a base-isolated structure equipped with additional inerters. By simplifying the structure-isolator-inerter system in terms of the two-degree-of-freedom (2DOF) model, the modal frequencies, mode shapes, damping ratios, and participation factors of the system are derived. Consequently, analytical seismic response solutions are formulated by the modal superposition method. Utilizing these analytical solutions, an extensive parametric study has been carried out to investigate the effect of supplement inerters on both the modal characteristics and seismic response of the structure-isolator-inerter system. There is a critical inertance leading to the zero second modal participation factor (ie, the disappearance of the second modal response). The associated critical inertance ratio is derived in closed form as well. Moreover, it is observed that the reduction of deformation of isolators by increasing the inertance may be offset by the increase in relative displacements of the superstructure. To circumvent this adverse effect, an optimal range of inertance is identified whereby both the deformation of isolators and the relative displacement of the superstructure are mitigated concurrently.  相似文献