唐山地区尾波Q值时空分布特征

利用首都圈地震数字台网2009年1月至2016年3月记录的地震波形资料,采用Sato尾波单次散射模型,固定尾波窗长,计算唐山地区尾波Q值,时间和空间上分析Q值分布特征,结果显示,Q值在空间分布上呈现明显的横向不均匀性,在较长孕震时间上呈现降低—升高—降低—发震的过程,且中强震易发生在Q值高低值交界区偏高值一侧,震群易发生在Q值相对较低区域。     

地层衰减定量模拟的地震物理模拟方法

Q值是描述地层衰减特征的重要地震物理参数,研究Q值对提高地震资料分辨率,提高地震成像精度具有重要意义.本文从地震物理模拟中模型材料的动力学特征出发,提出了一种地层衰减定量模拟的地震物理模拟方法.通过铝样验证了衍射校正方法的准确性,利用有机玻璃实验分析了不同测量方法求取Q值的测量精度问题,从而优选测量方法;然后基于复合材料的实验数据,建立复合材料配比与各物理参数之间的函数关系,利用该函数关系指导地层衰减定量模拟.结合单层地震物理模型和近地表地震物理模型,研究了模拟地震记录及其频谱特征与野外实际情况之间的相似性,基于建立的函数关系研究分析了地层衰减定量模拟的准确性.实验结果表明,基于地震衰减定量模拟方法构建近地表地震物理模型时,模型中模拟参数不仅与设计参数保持很好的一致性,同时具有很高的准确性,模拟地层的频谱衰减特征与野外地层保持一致.     

地震反Q滤波应用于碳酸盐岩储层特征描述

塔里木盆地塔河地区的奥陶系碳酸盐岩储层埋藏深,其深度超过5000 m,储集体类型以裂缝、缝洞为主,储层的纵向和横向上都具有极强的非均质性.这些特点导致反射地震数据的信噪比低、分辨率低,从而使得碳酸盐岩储层特征描述的难度增大.针对这些问题,本文运用稳定化反Q滤波方法对塔河地区的三维地震数据进行提高分辨率处理,同步实现地震振幅补偿和子波相位校正.处理结果与原始地震数据进行地震剖面面貌、储层内幕信息、断裂缝洞刻画等方面的直接对比,一方面展示反Q滤波方法在提高分辨率、提高弱反射能量、以及增强反射同相轴的空间连续性等方面的优势,同时展示稳定化反Q滤波方法能够提高对奥陶系碳酸盐岩缝洞储集体的特征描述精度.     

地震资料处理中的Radon变换及反Q滤波

Radon变换利用信号的横向相关性和信号根幅随炮检距变化的特征,提取有效反射信号同相轴,同时提取的零炮检距地震剖面,保留了地震记录的高频信息,达到了提高分辨率的目的。叠前反Q滤波是以FUTTERMAN衰减模型为理论基础,校正地震子波相位拉伸,补偿地震波频率和振幅的损失,达到提高地震资料分辨率和信噪比及改善同相轴连续性的目的。      

用于岩体质量评价的地震波Q值计算方法

利用地震记录中的衰减信息(波形与频谱)计算岩体的品质因子(Q值),对岩体质量进行准确评价,典型的方法有振幅法、上升时间法、频谱比法、质心频率偏移法。本文介绍了这些方法的原理,并对它们的稳定性、适用情况做出了评价。     

Seasonal trend analysis (STA) of MODIS vegetation index time series for the mangrove canopy of the Teacapan-Agua Brava lagoon system,Mexico

Monthly time series, from 2001 to 2016, of the Normalized Difference Vegetation Index (NDVI) and the Enhanced Vegetation Index (EVI) from MOD13Q1 products were analyzed with Seasonal Trend Analysis (STA), assessing seasonal and long-term changes in the mangrove canopy of the Teacapan-Agua Brava lagoon system, the largest mangrove ecosystem in the Mexican Pacific coast. Profiles from both vegetation indices described similar phenological trends, but the EVI was more sensitive in detecting intra-annual changes. We identified a seasonal cycle dominated by Laguncularia racemosa and Rhizophora mangle mixed patches, with the more closed canopy occurring in the early autumn, and the maximum opening in the dry season. Mangrove patches dominated by Avicennia germinans displayed seasonal peaks in the winter. Curves fitted for the seasonal vegetation indices were better correlated with accumulated precipitation and solar radiation among the assessed climate variables (Pearson’s correlation coefficients, estimated for most of the variables, were r ≥ 0.58 p < 0.0001), driving seasonality for tidal basins with mangroves dominated by L. racemosa and R. mangle. For tidal basins dominated by A. germinans, the maximum and minimum temperatures and monthly precipitation fit better seasonally with the vegetation indices (r ≥ 0.58, p < 0.0001). Significant mangrove canopy reductions were identified in all the analyzed tidal basins (z values for the Mann-Kendall test ≤ ?1.96), but positive change trends were recorded in four of the basins, while most of the mangrove canopy (approximately 87%) displayed only seasonal canopy changes or canopy recovery (z > ?1.96). The most resilient mangrove forests were distributed in tidal basins dominated by L. racemosa and R. mangle (Mann-Kendal Tau t ≥ 0.4, p ≤ 0.03), while basins dominated by A. germinans showed the most evidence of disturbance.     

Ocean iron fertilization: Why further research is needed

Despite large uncertainties in the fertilization efficiency, natural iron fertilization studies and some of the purposeful iron enrichment studies have demonstrated that Southern Ocean iron fertilization can lead to a significant export of carbon from the sea surface to the ocean interior. From an economic perspective the potential of ocean iron fertilization (OIF) is far from negligible in relation to other abatement options. Comparing the range of cost estimates to the range of estimates for forestation projects they are in the same order of magnitude, but OIF could provide more carbon credits even if high discount rates are used to account for potential leakage and non-permanence. However, the uncertainty about undesired adverse effects of purposeful iron fertilization on marine ecosystems and biogeochemistry has led to attempts to ban commercial and, to some extent, scientific experiments aimed at a better understanding of the processes involved, effectively precluding further consideration of this mitigation option. As regards the perspective of public international law, the pertinent agreements dealing with the protection of the marine environment indicate that OIF is to be considered as lawful if and to the extent to which it represents legitimate scientific research. In this respect, the precautionary principle can be used to balance the risks arising out of scientific OIF activities for the marine environment with the potential advantages relevant to the objectives of the climate change regime. As scientific OIF experiments involve only comparatively small negative impacts within a limited marine area, further scientific research must be permitted to explore the carbon sequestration potential of OIF in order to either reject this concept or integrate it into the flexible mechanisms contained in the Kyoto Protocol.