柯坪块体震源介质参数测定

应用2011年1月-2015年4月柯坪块体及周边数字地震台站（38°-42.5°N,75°-80.5°E）记录的3.0 ≤ M ≤ 5.0地震事件,结合柯坪块体介质品质因子和各台站场地响应,计算各地震应力降、地震矩、震源破裂半径、拐角频率等新震源参数,并研究各背景值变化特征及彼此间对应关系。结果表明：柯坪块体地区地震震级与地震矩、矩震级、震源尺度之间表现为较好的正相关性,与地震拐角频率之间呈负相关。地震矩与震源破裂尺度整体呈正相关,但当震源破裂尺度较小时,地震矩变化不大,当震源破裂尺度大于250 m时,地震矩随震源破裂尺度的增大变化较快。由柯坪块体应力降时间分布特征分析可知,研究区具有地震前应力降呈现高值异常、震后缓慢恢复低值的演化过程。     

2012年河北唐山M_S4.8地震前首都圈东部视应力时空变化特征

本文采用近震源Brune模式,采用国家数字测震台网数据备份中心提供的地震波形资料,测定了2011年1月至2012年5月期间首都圈东部85次ML≥2.0地震的视应力,分析了2012年4月28日河北唐山MS4.8地震前动力学参数的时空变化特征,并讨论了震源参数的标度关系。结果如下:1视应力时序变化显示,唐山MS4.8地震前首都圈东部视应力出现了明显的升高变化过程;2视应力空间分布显示,唐山MS4.8地震前,首都圈东部视应力在震源区出现了相对高值集中区。     

天山中东段地区震源参数的初步应用研究

采用多台多地震联合反演的方法,首先得到了新疆天山中东段地区2001年以来MS≥2.5的105次中小地震的震源谱,进而测定了地震矩、拐角频率与应力降等震源参数,并讨论了它们之间的相互关系。在此基础上开展了该研究区应力降时空变化的动态跟踪工作,最后对研究区2004年6月以前的应力降时空演化特征做了一定程度的探讨。分析表明,该地区的地震矩、拐角频率与应力降等震源参数与震级有一定的相关性,应力降的时空演化特征可以作为该地区今后地震趋势预测的一种新手段。     

2006年7月4日河北文安MS5.1地震前震中周围地区小震视应力随时间的变化

2006年7月4日河北文安发生MS5.1地震,震前的2001年10月始在震区附近形成了ML≥1.5地震空区,这次地震发生在该空区边缘。本文在近震源条件下,根据Brune模式,利用北京数字遥测地震台网观测到的波形资料,测定了该空区边缘发生的20次ML≥2.0地震的地震矩和地震能量,进而计算了地震视应力,分析了空区形成过程中这些地震的视应力随时间的变化。结果表明,2004年出现了明显的视应力升高过程。这说明该空区的形成伴随着应力的增强过程,可能具有预测意义。     

浙江地区水库地震与构造地震应力参数特征研究

利用浙江区域数字地震台网记录到的地震波数据,采用布龙模式下近震源记录计算震源谱参数的方法,系统测定了发生在温州珊溪水库、宁波皎口水库库区以及浙江地区构造地震共326次地震的应力降、视应力等参数。给出了两个水库区地震与构造地震的应力降与视应力参数特征,并进行了对比分析。初步研究发现,皎口地震的应力降和视应力值均低于浙江地区构造地震;珊溪水库地震与构造地震在应力降和视应力值上具有震级分段的特征:震级ML<4.0级的地震,同震级的应力降和视应力值两者相差不大,而震级ML>4.0级的地震,构造地震的应力降和视应力值均高于珊溪水库地震。此外,测定的应力降、视应力的对数与震级ML之间存在较好的线性关系。     

2008年、2009年大柴旦两次6级地震序列地震视应力特征

计算得到2008年、2009年大柴旦两次6级地震序列中109个ML≥3.0地震的视应力,两次序列主震视应力分别为5.1 MPa、3.4 MPa,平均视应力为0.48 MPa。2008年地震序列视应力的整体平均水平小于2009年地震序列,综合USGS及哈佛大学CMT给出的震源参数,发现两次地震震中相近,但震源深度有很大差异,2008年地震深度约25 km,而2009年地震震源深度约12 km,震源深度及发震构造的差异可能造成两次地震序列视应力的不同。     

2008年5月12日四川汶川8．0级地震前后震源区应力水平估计

根据地震力学和数字地震学理论,利用视应力和应力降,估算了2008年5月12日四川汶川MS8.0级地震前后震源区的应力水平,结果表明,震前震源区应力值约为1.5~2.0MPa,地震破裂过程中,由于断层发生错动过头,使地震发生后震源区应力低于动摩擦力,降至-1.2~-0.1MPa。     

红河断裂带两侧地块地震震源参数研究

利用云南区域数字地震遥测台网资料,采用Brune圆位错模型对1998年12月至2006年8月云南境内M≥3地震和越南北部M>2地震测算震源参数。结果表明,红河断裂两侧活动块体的地震活动和震源参数存在较为明显的差异。就地震矩与震级的标度关系而言,滇西南块体与美国加州圣安德列斯断层和滇西实验场及其周边地区的结果一致,但与华南块体和越南北部地区有差异;从应力降的测算结果看,华南块体西缘的云南及越南北部地区的年均值为7.29MPa,滇西南块体为4.48MPa,两块体北部地震的应力降大于南部地区,应力降由北向南逐渐减小;就地震位错年均值而言,华南块体为12.3mm/a,滇西南块体为6.6mm/a。     

河北文安Ms5.1地震前首都圈及邻区震源动力学参数时空变化特征

本文根据近震源条件下,由北京数字遥测地震台网观测到的波形资料,利用Brune模式,得到了2002年1月至2006年6月期间首都圈及邻近地区989次ML≥2.0地震的震源谱,测定了它们的拐角频率和零频幅值.通过相关计算公式,得到了破裂半径、地震矩、地震能量、应力降、视应力等震源动力学参数.分析了这些动力学参数的标度关系以...     

内蒙古中西部地区视应力特征分析

本文利用呼和浩特数字地震遥测台网7个子台记录的119个质量较高的地震事件资料,基于遗传算法,采用Atkinson方法、Moya方法,反演得到了地震的震源谱参数、震源参数。在此基础上,从视应力的定义出发,根据反演得到的震源谱参数以及地震能量与震级的相互关系,计算得到了119个地震的视应力。并对它们之间的相互关系进行了讨论,结果显示,应力降、视应力与震级具有较好的线性关系,震源半径、应力降与视应力具有一定的相关关系。内蒙古中西部地区的高应力降和视应力区域主要集中在研究区的西南部。     

SCIENCE CHINA Earth Sciences SUBJECT INDEX TO VOLUME 57(2014)

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Distribution of throughfall and stemflow in multi‐strata agroforestry,perennial monoculture,fallow and primary forest in central Amazonia,Brazil

The partitioning of rain water into throughfall, stemflow and interception loss when passing through plant canopies depends on properties of the respective plant species, such as leaf area and branch angles. In heterogeneous vegetation, such as tropical forest or polycultural systems, the presence of different plant species may consequently result in a mosaic of situations with respect to quantity and quality of water inputs into the soil. As these processes influence not only the water availability for the plants, but also water infiltration and nutrient leaching, the understanding of plant effects on the repartitioning of rain water may help in the optimization of land use systems and management practices. We measured throughfall and stemflow in a perennial polyculture (multi‐strata agroforestry), monocultures of peach palm (Bactris gasipaes) for fruit and for palmito, a monoculture of cupuaçu (Theobroma grandiflorum), spontaneous fallow and primary forest during one year in central Amazonia, Brazil. The effect on rain water partitioning was measured separately for four useful tree species in the polyculture and for two tree species in the primary forest. Throughfall at two stem distances, and stemflow, differed significantly between tree species, resulting in pronounced spatial patterns of water input into the soil in the polyculture system. For two tree species, peach palm for fruit (Bactris gasipaes) and Brazil nut trees (Bertholletia excelsa), the water input into the soil near the stem was significantly higher than the open‐area rainfall. This could lead to increased nutrient leaching when fertilizer is applied close to the stem of these trees. In the primary forest, such spatial patterns could also be detected, with significantly higher water input near a palm (Oenocarpus bacaba) than near a dicotyledonous tree species (Eschweilera sp.). Interception losses were 6·4% in the polyculture, 13·9 and 12·3% in the peach palm monocultures for fruit and for palmito, respectively, 0·5% in the cupuaçu monoculture and 3·1% in the fallow. With more than 20% of the open‐area rainfall, the highest stemflow contributions to the water input into the soil were measured in the palm monocultures and in the fallow. Copyright © 1999 John Wiley & Sons, Ltd.     

A Monte Carlo study of rainfall forecasting with a stochastic model

A procedure for short-term rainfall forecasting in real-time is developed and a study of the role of sampling on forecast ability is conducted. Ground level rainfall fields are forecasted using a stochastic space-time rainfall model in state-space form. Updating of the rainfall field in real-time is accomplished using a distributed parameter Kalman filter to optimally combine measurement information and forecast model estimates. The influence of sampling density on forecast accuracy is evaluated using a series of a simulated rainfall events generated with the same stochastic rainfall model. Sampling was conducted at five different network spatial densities. The results quantify the influence of sampling network density on real-time rainfall field forecasting. Statistical analyses of the rainfall field residuals illustrate improvement in one hour lead time forecasts at higher measurement densities.     

Anthropogenic Eutrophication and Red Tide Outbreak in Lacustrine Systems of the Kashmir Himalaya

Red tide, a recurrent phenomenon has become conspicuous in several Kashmir lake ecosystems since 1991. The responsible organism (Euglena pedunculata), a rare flagellate rediscovered in the Kashmir Himalaya (Khan 1993) caused first and unprecedented red tide outbreak, constituting a maximum of 96% of resident numerical phytoplankton density in Dal Lake. At present, conflicting hypotheses exist on the generation of causal assemblage(s) imparting redness to waters: Jeeji Bai (1991) linked its origin to acid precipitation – a fallout of burning oil‐fields during the Gulf War – whilst Khan (1993) holds local factor(s) responsible. Field/experimental studies support the latter contention that the influx of untreated sewage, in unison with warm temperatures, high levels of PhAR, iron and interruption to hydrological flow‐pattern together with absence/or reduction in grazing activity created conducive environmental milieu for red tide outbreak. Dal Lake “red tide” drifted the bloom‐inoculum to other waters, including Lake Wular, where additional ecological niches were carved out, threatening the aesthetic value and biological diversity of Kashmir lakes. Ecological monitoring indicates frequent seasonal red tide occurrence in Dal Lake (including summer‐autumn event of 1998) which testifies its unabated eutrophication status. Further studies are needed on ecological adaptability and biogeographic distribution of this rare and unique red tide‐causing flagellate.