盐水泥浆测井解释技术分析

大港油田盐水泥浆测井解释评价工作已有20余年的历史.本文论述在盐水泥浆中“时间推移测井”解释技术及“粗、细粒、低矿化度地层水的砂岩储集层复杂油层评价的新技术”.这些技术已在该油田使用,并经试油资料验证,油层解释符合率由原来的56.5％上升为93.6％,获得了显著的地质效果.     

新西兰韦恩加瓦河砾石的沉积环境、阶地断错和8级地震重复率

新西兰北岛南部韦恩加瓦河地区在晚更新世冰缘气候控制下,由沉积和侵蚀的交替作用形成较高较老的阶地。较低较新的阶地是在全新世中期以来的现代正常气候条件下形成的。这些阶地分别被怀拉拉帕断层水平错动297米、100米,57米和28米。距今10000年以来,怀拉拉帕断层的平均水平滑动速度为10毫米/年。1855年8级地震的重复率为1500年     

一种可能的棕闪煌斑岩变异新种—棕闪钠煌岩

浏阳县蕉溪岭岩体中发现富钠煌斑岩,Na_2O为4.05％,主要矿物钠长石为32—51％,棕闪石为25—37％,其他矿物钾长石2—8％,单斜辉石1—10％,黑云母0.5—10％,钛铁矿1—5％,可能是已知棕闪煌斑岩的一个变异新种棕闪钠煌岩。它与花岗岩体有空间上的共生关系,可能属蕉溪岭花岗岩熔离分异或结晶分异演化过程的产物。     

中国地震代表团赴新西兰访问考察

应新西兰国家研究科技部邀请，以国家地震局人事教育司司长李裕彻为团长的中国地震代表团于１９９３年１０月１０－２０日访问考察了新西兰。本文介绍了这次访问考察的概况，并根据访问期间了解到的情况，较详细地介绍了新西兰的防震减灾工作、防灾减灾机构及其职能、防震减灾研究等方面的情况。     

地球深部研究—地球科学发展的挑战与机遇

本文扼要地介绍了国际地球深部研究的发展及现状，简要地讨论了地球深部研究与地球科学相关学科的关系，力图说明及时地组织和开展地球深部研究是发展我国地球科学的新机遇，是迎接未来世纪挑战的正确选择。     

A Late Cretaceous polar dinosaur fauna from New Zealand

New fossils of dinosaurs and pterosaurs have been found in the conglomeratic facies of the Maungataniwha Member of the Tahora Formation (Campanian) of New Zealand. These derive from a large theropod, a sauropod, an ankylosaur and a pterosaur. Together with previously described material they indicate at least five, maybe seven, taxa from the Late Cretaceous terrestrial fauna of New Zealand. At that time New Zealand was an island near Antarctica, so this represents an insular, polar fauna.We assume a vicariance model for the origin of this fauna, which probably samples that present in Antarctica at the time New Zealand rifted away from it. The fauna differs from other well known Cretaceous Gondwana faunas in including an ankylosaur, but is similar to that from the Late Early Cretaceous of Queensland, Australia. The inclusion of both an ankylosaur and sauropod lend a relict, Early Cretaceous aspect to the fauna. There seems to be no particular similarity to known polar faunas from the Early Cretaceous of Victoria, Australia, or the Late Cretaceous of Alaska and Antarctica.Dinosaurs, both large and small, were capable of surviving in the cool to cold-temperate, seasonal climate of New Zealand at this time.     

Sediment variability and bed material sampling in gravel-bed rivers

In a 350 m wide reach of the braided, gravel-bed Ashley River, the surface layer of the bed material was sampled in 141 areas of homogeneous graded sediment along seven cross-sections, and 30 kg bulk samples were collected at 86 randomly selected locations along the cross-sections. At one location, a single 854 kg sample composed of 28 subsamples was also collected. Analysis of the single large sample indicate that accurate determination of mean grain size D at that site requires, desirably, a sample of ～ 100 kg, but that samples in which the weight of the largest stone is less than 5 per cent of the total weight have unbiased estimates of D. Spatial variability of bulk material is such that 228 and 50 samples are needed to estimate D to ± 10 and ± 20 per cent respectively of the true value; requirements for estimating inclusive graphic standard duration are only 11 and 3 respectively. The grain-size distribution of the surface layer is only weakly related to the bulk material beneath. The results of ‘Wolman sampling’ along 12 cross-sections at two pace intervals (average 120 stones per cross-section) indicate that estimation of overall surface D to ±10 and ±20 per cent would require sampling along 64 and 14 cross-sections respectively. It is concluded that accurate characterization of bed sediment in gravel-bed rivers is very demanding of labour and resources, and that careful planning is needed to ensure efficiency and meaningful results.     

Stratigraphic evidence for millennial-scale temporal clustering of earthquakes on a continental-interior fault: Holocene Mississippi River floodplain deposits, New Madrid seismic zone, USA

The earthquake cycles that characterize continental-interior areas that are far from active plate boundaries have proven highly cryptic and difficult to resolve. We used a novel paleoseismic proxy to address this issue. Namely, we reconstructed Holocene Mississippi River channels from maps of floodplain strata in order to identify channel perturbations reflective of major displacement events on the high-hazard and mid-plate Reelfoot thrust fault, New Madrid seismic zone, U.S.A. Only three discrete slip events are currently documented for the Reelfoot fault ( AD 900,  AD 1450, and AD 1812). This study extends this record and, thus, illustrates the utility of stratigraphic proxies as paleoseismic tools. We concurrently offer here some of the first quantified response times for tectonically induced channel pattern changes in large alluvial rivers.

We identified at least two cycles of pervasive meandering that were interrupted by channel-straightening responses occurring upstream of the Reelfoot fault scarp. These straightening responses initiated at 2244 BC +/− 269 to 1620 BC +/− 220 and  AD 900, respectively, and each records initiation of a period of Reelfoot fault slip after millennia of relative tectonic quiescence. The second (or New Madrid) straightening response was triggered by the previously known  AD 900 fault slip event, and this initial low sinuosity has been protracted until the modern day by the latter  AD 1450 and AD 1812 events. The first (or Bondurant) straightening response began a period of several hundred to  1400 years of low river sinuosity which evidences a similar period of multiple recurrent displacement events on the Reelfoot fault. These Bondurant events predate the existing paleoseismic record for the Reelfoot fault.

These data offer initial evidence that slip events on the Reelfoot fault were temporally clustered on millennial scales and, thus, offers the first direct evidence for millennial-scale clustering of earthquakes on a continental-interior fault. This carries additional ramifications. Namely, faults that have been quiescent and non-hazardous for millennia could re-enter an enduring period of recurrent hazardous earthquakes with little warning. Likewise, the Reelfoot fault also reveals evidence of temporal clustering of earthquakes on short-term cycles (months), as well as evidence for longer-term reactivation cycles (10⁴–10⁶ years). This introduces the possibility that temporal clustering could be hierarchical on some continental-interior faults.     

Integration of P- and SH-wave high-resolution seismic reflection and micro-gravity techniques to improve interpretation of shallow subsurface structure: New Madrid seismic zone

Shallow high-resolution seismic reflection surveys have traditionally been restricted to either compressional (P) or horizontally polarized shear (SH) waves in order to produce 2-D images of subsurface structure. The northernmost Mississippi embayment and coincident New Madrid seismic zone (NMSZ) provide an ideal laboratory to study the experimental use of integrating P- and SH-wave seismic profiles, integrated, where practicable, with micro-gravity data. In this area, the relation between “deeper” deformation of Paleozoic bedrock associated with the formation of the Reelfoot rift and NMSZ seismicity and “shallower” deformation of overlying sediments has remained elusive, but could be revealed using integrated P- and SH-wave reflection. Surface expressions of deformation are almost non-existent in this region, which makes seismic reflection surveying the only means of detecting structures that are possibly pertinent to seismic hazard assessment. Since P- and SH-waves respond differently to the rock and fluid properties and travel at dissimilar speeds, the resulting seismic profiles provide complementary views of the subsurface based on different levels of resolution and imaging capability. P-wave profiles acquired in southwestern Illinois and western Kentucky (USA) detect faulting of deep, Paleozoic bedrock and Cretaceous reflectors while coincident SH-wave surveys show that this deformation propagates higher into overlying Tertiary and Quaternary strata. Forward modeling of micro-gravity data acquired along one of the seismic profiles further supports an interpretation of faulting of bedrock and Cretaceous strata. The integration of the two seismic and the micro-gravity methods therefore increases the scope for investigating the relation between the older and younger deformation in an area of critical seismic hazard.