青藏高原东北部天然地震探测与岩石圈深部特征   总被引：10，自引：1，他引：10       下载免费PDF全文

薛光琦  钱辉  姜枚  宿和平  董英君  Gerard Wittlinger  Jerome Vergne  Georges Poupinet 《地球学报》2003,24(1):19-26

为了研究青藏高源东北部块体构造变形的深部驱动机制，笔者对青藏高原东北部的天然地震观测数据进行地震层析反演，并结合同一剖面的接收函数及各向异性结果进行讨论。介绍了ACH方法的基本原理，论述了由于印度板块向北俯冲的强大的持续作用力，造就了NE向俯冲到柴达木盆地之下的昆仑造山带，并发现在巴颜喀拉地体下方壳幔内的仰冲活动。壳幔内的低速体十分显著地出现在阿尼玛卿缝合线以北，深度可达300km。推断该低速体可能与昆仑断裂的深层的剪切作用有关。深部资料显示该区莫霍界面由北向南逐渐加深，这与青藏高原东北部的岩石圈减薄现象一致，而且与印度板块向北运动的远程效应有关。另外，地震层析结果及各向异性分析也支持青藏高原东北部主应力方向转为NE向的观点。  相似文献   

Thermal periodicities in the Venus atmosphere     

Jerome Apt  Johnny Leung 《Icarus》1982,49(3):427-437

A search was made for periodic fluctuations in the thermal brightness temperatures recorded by the Pioneer Venus orbiter's infrared radiometer. Data were averaged in 10 × 10° latitude-longitude bins for each of the 72 days the instrument was in operation. This time series of thermal brightness temperatures was then analyzed to determine the amplitude of fluctuations at periods from 2 to 64 days at four levels in the atmosphere (at the cloud tops and at approximately 70, 80, and 90 km). The amplitude of such fluctuations is small at equatorial latitudes and increases to a maximum at 60–70° latitude at most altitudes. The period of the highest amplitude fluctuation is 5.3±0.4 days (at all altitudes) except at 70–80°, where a 2.9-day period which appears to correspond to the polar dipole dominates the cloud-top channel. The amplitude of the periodic fluctuations is a maximum at the cloud tops, decreasing to a minimum at the 80-km channel, and increasing again at the 90-km channel.  相似文献   

Solar constant secular changes     

Kenneth H. Schatten  Jerome A. Orosz 《Solar physics》1990,125(1):179-184

Our recent model for solar constant secular changes suggests that over extended time intervals, a positive correlation of the solar constant with solar activity results. The positive correlation in this model is not associated with the direct result of active region, which may be in a close energy balance over their lifetimes, but rather is associated with global features - bright global faculae. These exist as both polar and network features on the solar disk. The high latitude faculae enable the solar constant to peak prior to sunspot maximum. Recent solar constant observations support the model's general trend. Using this model, we now calculate a proxy solar constant for: (1) the past four centuries, based upon the sunspot record, (2) the past nine centuries, based upon ¹⁴C observations and their relation to solar activity, and (3) the next decade, based upon a dynamo theory model for the solar cycle. The proxy solar constant data is tabulated as it may be useful for climate modelers studying global climate changes. This could be helpful in disentangling possible solar influences from any anthropogenic changes associated with trace gas increases in the terrestrial atmosphere. An important point for climate modelers to consider in fixing climate model parameters, is that the Sun has been relatively active and thus bright in the latter half of the 20th century, compared with the past few centuries.This paper was presented at the third meeting of the Solar Cycle Workshop, held in Sydney, Australia, January 9–13, 1989.Physics Dept., Univ. of Northern Colorado, U.S.A.  相似文献   

Short term evolution of coronal hole boundaries     

Jerome T. Nolte  Allen S. Krieger  Craig V. Solodyna 《Solar physics》1978,57(1):129-139

In an examination of the evolution of coronal hole boundaries on a time scale of 1 day, we find that 38% of all the boundaries of coronal holes observed near central meridan passage during the Skylab period shifted in location by >1° heliocentric in 1 day. Of these boundary changes, 70% were on a scale 3 times the average supergranulation cell size. However, large-scale shifts in the boundary locations also occurred, which involved changes in the X-ray emission from these areas of the Sun. X-ray emitting structures on the borders of isolated and evolving holes were less clearly defined than those on the boundaries of well-established, elongated holes. There were generally more changes in the boundaries of the most rapidly evolving holes, but no simple relationship between the amount of change and the rate of hole growth or decay.Skylab Solar Workshop post-doctoral appointee 1975–1976. The Skylab Solar Workshops are sponsored by NASA and NSF and managed by the High Altitude Observatory, National Center for Atmosoheric Research.  相似文献   

Soil evolution and subalpine ecosystem changes in the French Alps inferred from geochemical analysis of lacustrine sediments   总被引：1，自引：0，他引：1  

Brice Mourier  Jerome Poulenard  Christopher Carcaillet  David Williamson 《Journal of Paleolimnology》2010,44(2):571-587

This study aimed to reconstruct the history of soil development, ecosystem changes and associated erosional processes in a small mountain lacustrine basin at the decennial to millennial scale. Geochemical proxies of soil evolution were analysed in the Holocene lacustrine sediments and peats from Thyl Lake, Maurienne Valley, French Alps. Podzolization and chemical weathering processes were assessed using secondary Al- and Fe-bearing phases together with major and Rare Earth Elements (REE). The resulting proxy records, spanning ca. 4,400 years between 8.6 and 4.2 cal ka BP, indicate that progressive pedogenesis occurred after deglaciation in a relatively stable subalpine ecosystem. As shown by the associated increase in Al- and Fe-bearing phases and some REE fractions, the establishment of a mixed cembra pine ecosystem from ca. 7.2–6.5 ka BP was associated with enhanced podzolisation processes in the catchment. The progressive soil development was followed by a rapid transformation of the local environment and plant cover (the open waters of the lake were replaced by a confined peat environment) together with changes in forest fire regimes from ca. 6.8 ka BP. Depleted REE patterns, associated with low contents of secondary Al and Fe, suggest a decrease in chemical weathering and podzolization in the catchment at that time, possibly associated with local intensification of weathering and drainage processes in a relatively acidic peat environment. The higher variability of cembra pine and the increased abundance of sedge and other herbaceous plant remains in the lake sediment indicate semi-open vegetation environments from 5.7 cal ka BP onwards. Whereas fire events and plant cover appear to be significantly related, the soil processes seem primarily linked to vegetation composition, and secondarily to changes in fire regime.  相似文献   

Acoustic density measurements of consolidating cohesive sediment beds by means of a non-intrusive “Micro-Chirp” acoustic system     

Ho Kyung Ha  Jerome P.-Y. Maa  Charles W. Holland 《Geo-Marine Letters》2010,30(6):585-593

A non-intrusive “Micro-Chirp” acoustic system and a signal-processing protocol have been developed to estimate the bulk density of consolidating cohesive sediment beds. Using high-frequency (300–700 kHz) Chirp acoustic waves, laboratory measurements were conducted with clay–water mixtures. Because acoustic echo strength is proportional to variations in acoustic impedance, and the speed of sound in the clay bed hardly changed during consolidation, the bulk density could be successfully estimated without disturbing the sediment bed. Based on acoustic signal analysis, this study demonstrates that the reflection coefficient and bulk density at the water–sediment interface increase with consolidation time, and that a single speed of sound value can be used for practical bulk density estimation in muddy environments.  相似文献   

Review: Carbonate aquifers and future perspectives of karst hydrogeology in India   总被引：2，自引：0，他引：2  

Farooq Ahmad Dar  Jerome Perrin  Shakeel Ahmed  Allu China Narayana 《Hydrogeology Journal》2014,22(7):1493-1506

About 3 % of India’s total land surface is occupied by carbonate rocks which are mostly karstified and constitute a significant source of groundwater. The groundwater drawn from these aquifers matches the water demand of ~35 million people living in 106 districts of the country and also the water needs of livestock, irrigation and industry. The studies on karst in India carried out so far have mostly addressed geology, hydrology and groundwater contamination. A literature survey suggests that there is a need for detailed research, applying new approaches and techniques for proper carbonate aquifer identification, characterization and management. Such specific approaches will improve modeling, exploitation and protection of karst groundwater. An overview of the research carried out on groundwater resources of karst formations in India is presented, which also throws light on the protection of karst aquifers from existing anthropogenic activities such as mining and groundwater over-exploitation.  相似文献   

The effects of geological heterogeneities and piezometric fluctuations on groundwater flow and chemistry in a hard-rock aquifer, southern India   总被引：1，自引：0，他引：1  

Jerome Perrin  Shakeel Ahmed  Daniel Hunkeler 《Hydrogeology Journal》2011,19(6):1189-1201

Crystalline aquifers of semi-arid southern India represent a vital water resource for farming communities. A field study is described that characterizes the hydrodynamic functioning of intensively exploited crystalline aquifers at local scale based on detailed well monitoring during one hydrological year. The main results show large water-table fluctuations caused by monsoon recharge and pumping, high spatial variability in well discharges, and a decrease of well yields as the water table decreases. Groundwater chemistry is also spatially variable with the existence of aquifer compartments within which mixing occurs. The observed variability and compartmentalization is explained by geological heterogeneities which play a major role in controlling groundwater flow and connectivity in the aquifer. The position of the water table within the fracture network will determine the degree of connectivity between aquifer compartments and well discharge. The presented aquifer conceptual model suggests several consequences: (1) over-exploitation leads to a drop in well discharge, (2) intensive pumping may contribute to the hydraulic containment of contaminants, (3) groundwater quality is highly variable even at local scale, (4) geological discontinuities may be used to assist in the location of drinking-supply wells, (5) modeling should integrate threshold effects due to water-table fluctuations.  相似文献   

Aquaterra Incognita: Lost Land Beneath The Sea     

Jerome E. Dobson 《Geographical review》2014,104(2):123-138

The author proposes scientific recognition of an existing, previously undefined and unnamed global feature. Aquaterra is suggested as the new name for the lands that were alternately exposed and inundated as ice sheets advanced and retreated over the past 120,000 years. The vertical amplitude of sea level change amounts to 130 meters, and the aggregate global area of aquaterra equates to the continent of North America. The time period coincides with the total span during which modern humans are known to have existed.  相似文献   

Causes of Climate. John G. Lockwood; The Atmosphere. Frederick K. Lutgens and Edward J. Tarbuck; Land in America. Richard N. L. Andrews,Editor     

Jay Harman  Jerome M. Clemens  Paul F. Mattingly 《自然地理学》2013,34(2):197-200

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