Evolution of sedimentary environments of the middle Jiangsu coast, South Yellow Sea since late MIS 3

An evolutionary model of sedimentary environments since late Marine Isotope Stage 3 （late MIS 3, i.e., ca. 39 cal ka BP） along the middle Jiangsu coast is presented based upon a reinterpretation of core 07SR01, new correlations between adjacent published cores, and shallow seismic profiles recovered in the Xiyang tidal channel and adjacent northern sea areas. Geomorphology, sedimentology, radiocarbon dating and seismic and sequence stratigraphy are combined to confirm that environmental changes since late MIS 3 in the study area were controlled primarily by sea-level fluctuations, sediment discharge of paleo-rivers into the South Yellow Sea （SYS）, and minor tectonic subsidence, all of which impacted the progression of regional geomorphic and sedimentary environments （Le., coastal barrier island freshwater lacustrine swamp, river floodplain, coastal marsh, tidal sand ridge, and tidal channel）. This resulted in the formation of a fifth-order sequence stratigraphy, comprised of the parasequence of the late stage of the last interstadial （Para-Sq2）, including the highstand and forced regressive wedge system tracts （HST and FRWST）, and the parasequence of the postglacial period （Para-Sql）, including the transgressive and highstand system tracts （TST and HST）. The tidal sand ridges likely began to develop during the postglacial transgression as sea-level rise covered the middle Jiangsu coast at ca. 9.0 cal ka BP. These initially submerged tidal sand ridges were constantly migrating until the southward migration of the Yellow River mouth to the northern Jiangsu coast during AD 1128 to 1855. The paleo-Xiyang tidal channel that was determined by the paleo-tidal current field and significantly different from the modern one, was in existence during the Holocene transgressive maxima and lasted until AD 1128. Following the capture of the Huaihe River in AD 1128 by the Yellow River, the paleo-Xiyang tidal channel was infilled with a large amount of river-derived sediments from AD 1128 to 1855, causing the emergence of some of the previously submerged tidal sand ridges. From AD 1855 to the present, the infilled paleo-Xiyang tidal channel has undergone scouring, resulting in its modern form. The modern Xiyang tidal channel continues to widen and deepen, due both to strong tidal current scouring and anthropogenic activities.     

Source parameters of small and moderate earthquakes in the area of the 2009 L’Aquila earthquake sequence (central Italy)

The main goal of this study is to provide moment tensor solutions for small and moderate earthquakes of the 2009 L’Aquila seismic sequence (central Italy). The analysis was performed by using data coming from the permanent Italian seismic network run by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the “Cut And Paste” (CAP) method based on broadband waveform inversion. Focal mechanisms, source depths and moment magnitudes are determined through a grid search technique. By allowing time shifts between synthetics and observed data the CAP method reduces dependence of the solution on the assumed velocity model and on earthquake location. We computed seismic moment tensors for 312 earthquakes having local magnitude in the range between 2.7 and 5.9. The CAP method has made possible to considerably expand the database of focal mechanisms from waveform analysis in the lowest magnitude range (i.e. in the neighborhood of magnitude 3) without overlooking the reliability of results. The obtained focal mechanisms generally show NW–SE striking focal planes in agreement with mapped faults in the region. Comparisons with the already published solutions and with seismological and geological information available allowed us to proper interpret the moment tensor solutions in the frame of the seismic sequence evolution and also to furnish additional information about less energetic seismic phases. Focal data were inverted to obtain the seismogenic stress in the study area. Results are compatible with the major tectonic domain. We also obtained a relation between moment and local magnitude suitable for the area and for the available magnitude range.     

浅谈芦山地震

地震序列是对地震现象的回顾性描述,只有在地震序列结束后它才有可能被确切无疑地判定.鉴于龙门山断裂带或地震带的整体性、统一性和系统性,不可否认在其西南段发生的芦山地震是与汶川地震一样的同属于龙门山断裂带的事件.鉴于芦山地震的震源位置、震源机制、震级大小和破裂区覆盖的范围,目前可认为它是汶川地震迄今最大的余震.鉴于地震序列的判定是对地震现象的唯象的描述,有相当的任意性,对芦山地震究竟是"新的主震"还是"汶川余震"的"讨论"实质上是在根据经验判定地震的类型,即使目前看"主震说"提出的4条"论据"明显缺乏说服力,"余震说"比较有说服力,但最后都需要等到地震序列结束之后才有可能"定论".作者认为,相对于需要等到地震序列结束之后才能"定论"、甚而在地震序列结束之后未必能"定论"的芦山地震究竟是"新的主震"还是"汶川余震"问题,应当更为关注芦山地震的发生引出的一些重要的亟待研究的科学问题与防震减灾问题.     

2013年甘肃岷县漳县M_S6.6地震及其余震序列重定位

使用甘东南地区三维速度模型,利用三维网格搜索法和双差地震定位法对2013年7月22日甘肃岷县漳县MS6.6地震及其震后三天的余震序列进行了精确定位,结合地质构造资料对本次地震的发震构造进行了初步研究。其结果显示:主震的震中位置为34.54°N,104.189°E,震源深度13.5km;余震震中呈NW或NWW方向分布,与临潭-宕昌断裂的走向基本吻合,主要分布于5～20km的深度,震中在深度剖面上呈SW向;发震断裂为倾向SW的隐伏断层,位于临潭-宕昌断裂NE方向,距临潭-宕昌断裂约20km。     

用最大熵谱法分析玉门地震序列的频谱变化

采用Burg最大熵谱分析方法对玉门地震序列进行了频谱分析计算。结果显示:当主震发生时,频谱主频向高频方向变化,当整个序列接近尾声时,频率逐渐恢复。这个结果可解释为,随着应力的积累,孕震区介质部分裂隙闭合,挤出裂隙水,密度相对增大,品质因数提高,高频成分的衰减降低,使频谱的主频率移向高频。     

甘肃岷县漳县M_S6.6地震序列波速比变化特征研究

收集了甘肃岷县漳县MS6.6地震序列固定台站和震后6个流动台站震相观测报告,提取了P波、S波走时信息,采用多台和达法计算该地震序列波速比,发现震后较强余震发生前波速比趋势性下降的特征。这对后续震情跟踪和趋势判定过程中强余震预测有一定的参考价值和指示意义。     

地震的"序列归属"问题与ETAS模型——以唐山序列为例

历史上发生过强震地区的余震活动可能持续较长时间,而余震序列在何时可被看作正常的"背景地震活动",即"序列归属"问题在地球动力学和地震物理中有重要意义.时-空"传染型余震序列"(ETAS)模型可分离"背景"地震和"丛集"地震,并用概率形式表示作为相应事件的可能性,为考察此问题提供了可能.本文以1976年唐山M_S7.8地震序列为例,对唐山地区1970年以来的M_L4.0以上地震进行了时-空ETAS模型拟合,并以2010年以来发生的3次M_S4.0以上地震为例讨论了它们的"序列归属"问题.研究结果显示,3次M_S4.0以上地震的背景地震概率分别为0.72、0.88和0.76,表明它们作为1976年唐山M_S7.8的余震的可能性较低,更可能为背景地震.     

Tracking of facial deformations in multi-image sequences with elimination of rigid motion of the head

The paper deals with measurement of human facial deformations from synchronized image sequences taken with multiple calibrated cameras from different viewpoints. SIFT (Scale Invariant Feature Transform) keypoints are utilized as image feature points in the first place to determine spatial and temporal correspondences between images. If no temporal match is found for an image point by keypoint matching, then the tracking of the point is switched to least squares matching provided the point has one or more spatial corresponding points in the other views of the previous frame. For this purpose, a new method based on affine multi-image least squares matching is proposed where multiple spatial and temporal template images are simultaneously matched against each search image and part of the spatial template images also change during adjustment. A new method based on analyzing temporal changes in the image coordinates of the tracked points in multiple views is then presented for detecting the 3-D points which move only rigidly between consecutive frames. These points are used to eliminate the effect of rigid motion of the head and to obtain the changes in the 3-D points and in the corresponding image points due to pure deformation of the face. The methods are thoroughly tested with three multi-image sequences of four cameras including also quite large changes of facial deformations. The test results prove that the proposed affine multi-image least squares matching yields better results than another method using only fixed templates of the previous frame. The elimination of the effect of rigid motion works well and the points where the face is deforming can be correctly detected and the true deformation estimated. A method based on a novel adaptive threshold is also proposed for automated extraction and tracking of circular targets on a moving calibration object.     

非等间距无偏GM（1,1）模型在建筑沉降预测中的应用

将非等间距数列转化为等间距数列,并建立无偏GM（1,1）模型.通过对非等间距数列的处理,得到适合GM（1,1）建模的等时距数列,并在GM（1,1）模型的基础上,给出非等间距无偏GM（1,1）建模的具体步骤.从理论上证明无偏GM（1,1）能消除GM（1,1）模型的固有偏差,拓宽GM（1,1）的使用范围.最后将模型应用于实际建筑沉降预测中,研究结果表明非等间距无偏（1,1）模型精度高、实用性强.