对2008年1月9日西藏改则东6．9级地震中期预测的反思

2007年12月中国地震预测咨询委员会预测2008--2009年在西藏拉萨-申扎一带及附近可能发生7级地震。2008年1月9日西藏改则东6．9级地震,粗略符合原预测。所用的预测方法是倍周期性、静中动判据和地球物理灾害链。     

UXO target area identification with hidden Markov models

Site characterization activities at potential unexploded ordnance (UXO) sites rely on sparse sampling collected as geophysical surveys along strip transects. From these samples, the locations of target areas, those regions on the site where the geophysical anomaly density is significantly above the background density, must be identified. A target area detection approach using a hidden Markov model (HMM) is developed here. HMM’s use stationary transition probabilities from one state to another for steps between adjacent locations as well as the probability of any particular observation occurring given each possible underlying state. The approach developed here identifies the transition probabilities directly from the conceptual site model (CSM) created as part of the UXO site characterization process. A series of simulations examine the ability of the HMM approach to simultaneously determine the target area locations within each transect and to estimate the unknown anomaly intensity within the identified target area. The HMM results are compared to those obtained using a simpler target detection approach that considers the background anomaly density to be defined by a Poisson distribution and each location to be independent of any adjacent location. Results show that the HMM approach is capable of accurately identifying the target locations with limited false positive identifications when both the background and target are intensities are known. The HMM approach is relatively robust to changes in the initial estimate of the target anomaly intensity and is capable of identifying target locations and the corresponding target anomaly intensity when this intensity is approximately 60% higher than the background intensity at intensities that are representative of actual field sites. Application to data collected from a wide area assessment field site show that the HMM approach identifies the area of the site with elevated anomaly intensity with few false positives. This field site application also shows that the HMM results are relatively robust to changes in the transect width.     

滦平盆地桑园营子露头剖面沉积层序的Markov链模拟

桑园营子露头剖面具有同沉积断层控制的近源、粗粒、陡坡型浅水扇三角洲体系的沉积特征。根据 Markov过程的基本原理 ,认识到桑园营子剖面出露完整的扇三角洲前缘沉积组合( C — C 旋回 )各岩性相之间的转移具有 Markov性质 ,利用转移概率矩阵法及差值矩阵法对该沉积组合进行 Markov链模拟 ,得出了理想的垂向沉积层序模式图。该模式图与实际地层层序吻合较好 ,反映了各岩性相的空间展布特征 ,建立了沉积环境的演化序列。     

用坐标转换法解算线形锁

根据线形锁的基本特点,提出了一种利用坐标转换原理进行线形锁（包括双定向线形锁、单定向线形锁、无定向线形锁）精密平差计算的新方法。     

德令哈盆地早侏罗世冲积扇—扇三角洲沉积体系及其马尔科夫链分析

德令哈盆地下侏罗统含煤磨拉石盆地组合是在以冲积扇—扇三角洲沉积体系为主的沉积环境下发育起来的。简要报道研究区冲积扇—扇三角洲体系沉积及其组合特征 ,在此基础上借助马尔科夫链建立冲积扇—扇三角洲体系沉积旋回的结构模式 ,并探讨该结构模式的地质意义。     

中国大陆8级大震矩形链规律及其应用研究

基于对中国大陆已发生的22个8级大震的研究,发现8级大震的发生有其规律性,这种规律性表现在8级大震发生的年份可组成一个矩形地震链,这种规律可用来对中国大陆8级大震进行预测。     

珠江口盆地Site4B柱状沉积物中长链烷基二醇和酮醇类化合物的检出及意义

珠江口盆地Site4B沉积物中（65~300 cm）检出了1,15-C30（ω16）和1,15-C32（ω18）烷基二醇和酮醇,总的长链烷基二醇和酮醇含量分别为0.026～4.373 μg/g干沉积物和0.005～1.549 μg/g干沉积物。沉积物剖面上检测到的1,15-C30烷基二醇（-26.6‰±0.9‰）相对于来自陆源高等植物的C30直链烷基醇（-32.8‰±1.5‰）较正的碳同位素特征反映了这类化合物可能不是来自陆源高等植物;同时沉积物中未检出在黄绿藻中相对长链烷基二醇和酮醇更丰富的甾醇,且沉积物浅表层中（0~65 cm）未检出长链烷基二醇和酮醇类化合物,表明现今沉积物中几乎没有黄绿藻的贡献,和沉积物所处的寡营养盐（不适宜藻类生长发育）的陆坡位置相吻合。沉积物中1,15-C30烷基二醇（-24.6‰～-28.4‰）和海洋细菌来源的短链脂肪酸 (-25.5‰～-28.6‰)具有相似的碳同位素组成,表明了海洋细菌是其可靠来源。Site4B沉积物中1,15-C30和1,15-C32烷基酮醇和二醇具有非常好的相关性,表明了它们可能来自相同的生物来源或者来自相关性较好的不同生源,而不是通过对应的二醇氧化生成,因为在65~95 cm的氧化环境中酮醇比例没有明显增高。Site4B沉积物中二醇参数和酮醇参数的变化非常相似,结合含量分布特征反映了古海水温度以及淡水入侵的双重影响,即较高的二醇参数及较高的二醇含量和较低的二醇参数及较低的二醇含量都可能反映了古海水温度是主要影响因素;而较低的二醇参数及较高的二醇含量则可能反映了淡水的侵入是主要影响因素。