2008年盈江地震序列的震源参数和震源机制相关系数研究

基于云南数字地震台网记录的2008年盈江地震序列的数字波形资料,采用波谱分析方法和Brune震源模型,得到盈江地震序列的震源参数。利用两次地震事件的相同台站的震源谱参数（零频振幅）计算谱振幅相关系数,据此对地震的震源机制进行聚类分组,并收集和对比地震序列已知的震源机制解结果,发现每组内震源机制解P轴的相关性较好,且相关系数越大,P轴的方位角就越接近。将盈江地区划分为三个研究区,联合震源参数的应力降和聚类分组中每组的平均震源机制解结果研究地震序列发生过程中应力的释放水平和应力场方向变化特征。结果表明：不同阶段震源机制解类型的变化和转化特征一定程度上反映了孕震过程中区域应力场随时间的变化特征,并且地震震源机制解类型在时间段上的集中并向区域构造应力场方向转换的现象可能是发生强震的标志。震源机制解分组类型和对应类型的地震的应力降有一定依赖关系,震源机制解类型反映的应力场与区域应力场接近的地震应力降高,震源机制解类型反映的应力场与区域应力场差距较大的地震应力降普遍较低。     

The Sunda Shelf—A Submerged Amazon Basin?

A crucial and debatable issue in paleoclimatology is the change of terrestrial vegetation and the role of its carbon storage in glacial cycles. In the modern world, the Amazon Basin hosts the largest tropical rainforest and plays a major role of carbon sink, but during the glacial times another large tropical rainforest must have formed in the then emerged Sunda Shelf, SE Asia, and significantly changed the global carbon cycling. Accordingly, ocean drilling expeditions to the Sunda Shelf are being proposed in order to investigate the sea level changes, evolution of river network, vegetation and carbon storage, as well as biogeography of the tropical region over the last millions of years.     

Sea-level changes,coastal dune building and sand drift,North-Western Jutland,Denmark

Christiansen, C. & Bowman, D.: Sea-level changes, coastal dune building and sand drift, North-Western Jutland, Denmark. Geografisk Tidsskrift 86: 28–31. Copenhagen, June 1986.

Two main models linking dune building and sea level changes have so far been proposed. Application of the low sea level model suggests that the major Danish dune building period from 1550 to 1750 need not necessarily be the result of human activity. The dune building period is probably related to a low sea level and the reworking of exposed shallow marine sand.     

玉树地区两次强震序列应力降对比研究

利用青海省数字地震台网记录到的玉树地区2006年5级强震群地震和2010年7．1级地震的数字波形资料,计算了这2次地震序列应力降值,并进行了对比,发现应力降值在中强余震前都出现较明显的变化,同时随着地震的衰减,应力降值也逐渐减小。     

Study on Precise Location and Structure of Earthquakes in the Shanxi Reservoir,Zhejiang Province

The Shanxi reservoir earthquakes are significant seismic events in southern Zhejiang Province in recent years, an area with fewer and weaker earthquakes. The seismicity showed an intermittent characteristic and group distribution. The epicenters located by the seismic network did not show a predominant direction and the seismogenic structure is not clear. In the study, the nonlinear imaginary wave travel time equation was linearized and solved, and the source position, initial imaginary velocity and travel ...     

Late Cretaceous paleoenvironmental evolution of the Tarfaya Atlantic coastal Basin,SW Morocco

Lithological evidence, benthic foraminiferal census counts, and X-ray fluorescence (XRF) scanner-derived elemental data were integrated with planktonic foraminiferal biostratigraphy and bulk carbonate stable isotopes to retrace the Turonian to early Campanian paleoenvironmental evolution and sea-level history of the Tarfaya Atlantic coastal basin (SW Morocco). The lower Turonian is characterized by laminated organic-rich deposits, which contain impoverished benthic foraminiferal assemblages, reflecting impingement of the oxygen minimum zone on the shelf during a sea-level highstand. This highstand level is correlated to the global transgressive pulse above the sequence boundary Tu1. The appearance of low-oxygen tolerant benthic foraminiferal assemblages dominated by Gavelinella sp. in the middle to upper Turonian indicates an improvement in bottom water oxygenation, probably linked to offshore retraction of the oxygen minimum zone during a regressive phase. This interval is marked by major regressive events expressed by a series of erosional truncations associated with the prominent sequence boundaries Tu3 and/or Tu4. Dysoxic–anoxic conditions recorded in the upper Santonian of the Tarfaya Basin coincide with the eustatic sea-level rise prior to Sa3 sequence boundary. The lower Campanian transgression, only recorded in the southern part of the Tarfaya Basin, coincided with substantial deepening, enhanced accumulation of fine-grained clay-rich hemipelagic sediments and improved oxygenation at the seafloor (highest diversity and abundance of benthic foraminiferal assemblages). Stable isotope data from bulk carbonates are tentatively correlated to the English Chalk carbon isotope reference curve, in particular the Hitch Wood Event in the upper Turonian, the Navigation Event in the lower Coniacian, the Horseshoe Bay Event in the Santonian and the Santonian/Campanian Boundary Event.     

断层滑动速率,地震重复时间和平均应力降

本文综述了国内外大地震复发间隔研究的现状，系统整理了中国大陆活断层滑运速率，已发现的古地震遗迹及古地震复发间隔，结果表明，在滑动速率较在的活断层发现的古地震复发间隔较短，Ｋａｎａｍｏｒｉ和Ａｌｌｅ（１９８５）研究了具有大范围重复时间（２０年到几千年）的板内大地震的震源参数，发现复发间隔较长的大地震具有较高的平均应力降，我们在实验室内研究了应变速率不同时固体围压三轴压缩下完整花岗岩破裂后的粘滑现象。     

Wave train model for knickpoint migration

Rivers respond to a drop in their base level by incising the topography. The upstream propagation of an incision, as usually depicted by a knickpoint migration, is thought to depend on several parameters such as the drainage area, lithology, and the amplitude of the base level drop. We first investigate the case of the Messinian Salinity Crisis that was characterized by the extreme base level fall (1500 m) of the Mediterranean Sea at the end of the Miocene. The response of drainage areas of three orders of magnitude (10³ to 10⁶ km²) highlights the dominant role of the drainage area (with a square root relationship) in controlling the knickpoint migration after a base level fall. A compilation of mean rates of knickpoint propagation for time durations ranging from 10² to 10⁷ years displays a similar relationship indicating that successive wave trains of knickpoint can migrate in a river: first, wave trains linked to the release of the alluvial cover and then, wave trains related to the bedrock incision, which correspond to the real time response of rivers. Wave trains with very low retreat rates (long lived knickpoints > 1 My) rather correspond to the response time of regional landscape.     

Cloud drop spectra at different levels and with respect to cloud thickness and rain

Measurements on drop size were made in cumulus clouds over Pune (inland region) during the summer monsoon seasons. In this paper, the measurements of the cloud drop spectra made in non-raining clouds at different levels and for different thickness have been studied. Also, those on the days with rain and with no rain (the rain being observed within the clouds) have been compared. The average spectra broadened with height. The concentration of drops >50 μm (N_L), liquid water content (LWC), mean volume diameter (MVD) and dispersion increased with height. The concentration of drops <20 μm (N_S) and total concentration (N_T) decreased with height. The spectra were broader, while N_S and N_T are smaller and the other parameters are greater for thicker clouds as compared to those for thinner. The spectra were broader, while N_S and N_T are smaller and the other parameters are greater on the days with rain with respect to those on the days with no rain. The distributions were bimodal at higher levels, for thicker clouds and on the days with rain, while they were unimodal at lower levels, for thinner clouds and on the days with no rain. The variations of the cloud drop spectra, preceding rain, at initial stage of rain and following rain are discussed.     

汾渭地震带强震震源参数的确定

目的是计算汾渭地震强震的震源参数。所用的方法是根据断裂力学的有关公式分析断裂扩展过程中应力和位移的变化,计算结果表明地震多数是在低初始应用作用下发生的（大约１００×１０＾５Ｐａ）,而且该方法在原理上是可行的。