Near-infrared imaging in H2 of molecular (CO) outflows from young stars     

Jochen Eislöffel  Christopher J. Davis 《Astrophysics and Space Science》1995,233(1-2):59-62

We have imaged several known molecular (CO) outflows in H₂ v=1-0 S(1) and wide-band K in order to identify the molecular shocks associated with the acceleration of ambient gas by outflows from young stars. We detected H₂ line emission in all the flows we observed: L 1157, VLA 1623, NGC 6334I, NGC 2264G, L 1641N and Haro 4-255. A comparison of the H₂ data with CO outflow maps strongly suggests that prompt entrainment near the head of a collimated jet probably is the dominant mechanism for producing the CO outflows in these sources.  相似文献   

The densest prestellar condensations: H2CO Studies ofρ Oph B1     

M. Barsony  D. Sasselov  S. Rucinski  E. Bloemhof  L. -A. Nyman 《Astrophysics and Space Science》1995,233(1-2):51-54

We present new images of the well-known molecular outflow and Herbig-Haro complex L 1551-IRS 5. Deep, high-resolution images of the central region of the flow in [SII] 6716,6731 and H (6565 Å) are complemented by a mosaic of much of the CO outflow in H₂ v=1-0 S(1). While the optical data trace the intermediate-to-high excitation shocks in the flow (v _shock > 30 – 50 km s^–1), the near-IR data reveal the lower-excitation, molecular shocks (v _shock 10–50 km s^–1). In particular, the H₂ data highlight the regions where the flow impacts and shocks ambient molecular gas.  相似文献   

井下记录的PP和SS震相     

乌统昱  赵惠君 《地震地磁观测与研究》1992,13(2):20-26

本文在系统分析静海台井下地震记录图的基础上,发现并解决了具有一定实际和理论意义的两个问题:其一是证明了最初误认为是干扰的“双脉冲”图形实际上均是微地震。从而指出研究静海周围地区的地震活动性应考虑微震活动问题。其二确认静海周围地区微震波形的4个主要震相是P、PP、S和SS,并对地面反射波PP和SS能够观测到的条件作了初步分析,其结果进一步说明井下地震记录较之地面记录更为“逼真”,复杂和丰富。  相似文献   

Geophysical methods applied to fault characterization and earthquake potential assessment in the Lower Tagus Valley, Portugal     

Joo Carvalho  Joo Cabral  Rui Gonalves  Luís Torres  Luís Mendes-Victor 《Tectonophysics》2006,418(3-4):277-297

The study region is located in the Lower Tagus Valley, central Portugal, and includes a large portion of the densely populated area of Lisbon. It is characterized by a moderate seismicity with a diffuse pattern, with historical earthquakes causing many casualties, serious damage and economic losses. Occurrence of earthquakes in the area indicates the presence of seismogenic structures at depth that are deficiently known due to a thick Cenozoic sedimentary cover. The hidden character of many of the faults in the Lower Tagus Valley requires the use of indirect methodologies for their study. This paper focuses on the application of high-resolution seismic reflection method for the detection of near-surface faulting on two major tectonic structures that are hidden under the recent alluvial cover of the Tagus Valley, and that have been recognized on deep oil-industry seismic reflection profiles and/or inferred from the surface geology. These are a WNW–ESE-trending fault zone located within the Lower Tagus Cenozoic basin, across the Tagus River estuary (Porto Alto fault), and a NNE–SSW-trending reverse fault zone that borders the Cenozoic Basin at the W (Vila Franca de Xira–Lisbon fault). Vertical electrical soundings were also acquired over the seismic profiles and the refraction interpretation of the reflection data was carried out. According to the interpretation of the collected data, a complex fault pattern disrupts the near surface (first 400 m) at Porto Alto, affecting the Upper Neogene and (at least for one fault) the Quaternary, with a normal offset component. The consistency with the previous oil-industry profiles interpretation supports the location and geometry of this fault zone. Concerning the second structure, two major faults were detected north of Vila Franca de Xira, supporting the extension of the Vila Franca de Xira–Lisbon fault zone northwards. One of these faults presents a reverse geometry apparently displacing Holocene alluvium. Vertical offsets of the Holocene sediments detected in the studied geophysical data of Porto Alto and Vila Franca de Xira–Lisbon faults imply minimum slip rates of 0.15–0.30 mm/year, three times larger than previously inferred for active faults in the Lower Tagus Valley and maximum estimates of average return periods of 2000–5000 years for M 6.5–7 co-seismic ruptures.  相似文献   

Deep seismic reflection study over the Vindhyans of Rajasthan: Implications for geophysical setting of the basin     

B Rajendra Prasad  V Vijaya Rao 《Journal of Earth System Science》2006,115(1):135-147

This paper presents results of high-resolution deep seismic reflection profiling of the Proterozoic Vindhyan basin of the Rajasthan area along the Chandli-Bundi-Kota-Kunjer profile. Seismic images have been used to estimate the thickness of Vindhyan strata as well as to understand the tectonic framework of the basin. The results are constrained by gravity, magnetic and magnetotelluric data. The study reveals gentle SE-dipping reflection bands representing the Vindhyan strata. The seismic sections depict gradual thickening of the Vindhyan succession towards southeast from Bundi. The velocities of the upper and lower Vindhyans are identified as 4.6-4.8 km/s and 5.1-5.3 km/s. The NW limit of the Vindhyan basin is demarcated by the Great Boundary Fault (GBF) that manifests as a 30 km wide NW dipping thrust fault extending to a depth of 30 km.  相似文献   

Crust and upper mantle structure of a continental backarc: central North Island, New Zealand   总被引：3，自引：0，他引：3  

W. R. Stratford  T. A. Stern 《Geophysical Journal International》2006,166(1):469-484

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Crustal structure across the Grand Banks–Newfoundland Basin Continental Margin – II. Results from a seismic reflection profile     

K. W. Helen Lau  Keith E. Louden  Sharon Deemer  Jeremy Hall  John R. Hopper  Brian E. Tucholke  W. Steven Holbrook  Hans Christian Larsen † 《Geophysical Journal International》2006,167(1):157-170

New multichannel seismic reflection data were collected over a 565 km transect covering the non-volcanic rifted margin of the central eastern Grand Banks and the Newfoundland Basin in the northwestern Atlantic. Three major crustal zones are interpreted from west to east over the seaward 350 km of the profile: (1) continental crust; (2) transitional basement and (3) oceanic crust. Continental crust thins over a wide zone (∼160 km) by forming a large rift basin (Carson Basin) and seaward fault block, together with a series of smaller fault blocks eastwards beneath the Salar and Newfoundland basins. Analysis of selected previous reflection profiles (Lithoprobe 85-4, 85-2 and Conrad NB-1) indicates that prominent landward-dipping reflections observed under the continental slope are a regional phenomenon. They define the landward edge of a deep serpentinized mantle layer, which underlies both extended continental crust and transitional basement. The 80-km-wide transitional basement is defined landwards by a basement high that may consist of serpentinized peridotite and seawards by a pair of basement highs of unknown crustal origin. Flat and unreflective transitional basement most likely is exhumed, serpentinized mantle, although our results do not exclude the possibility of anomalously thinned oceanic crust. A Moho reflection below interpreted oceanic crust is first observed landwards of magnetic anomaly M4, 230 km from the shelf break. Extrapolation of ages from chron M0 to the edge of interpreted oceanic crust suggests that the onset of seafloor spreading was ∼138 Ma (Valanginian) in the south (southern Newfoundland Basin) to ∼125 Ma (Barremian–Aptian boundary) in the north (Flemish Cap), comparable to those proposed for the conjugate margins.  相似文献   

Three-dimensional structure across the Tintina strike-slip fault, northern Canadian Cordillera, from seismic refraction and reflection tomography     

Colin A. Zelt  Robert M. Ellis  Barry C. Zelt 《Geophysical Journal International》2006,167(3):1292-1308

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探地雷达(GPR)在海南岛东北部海岸带调查中的应用 ^*   总被引：2，自引：0，他引：2  

殷勇  朱大奎  I.P.Martini 《第四纪研究》2006,26(3):462-469

对海南岛东北部海岸带调查采用了探地雷达(GPR)研究海岸带沙体的结构、展布和沉积序列,取得了很好的效果。文章通过和有限的露头资料对比以及对反射波形态、结构的研究,确定了海滩脊、海岸沙丘的反射特征以及潜水面的位置。雷达图像显示五龙港古海滩脊由亚水平、不连续、高振幅和透镜状反射波组成;木兰头海岸沙丘已受到人类活动的扰动,短的、陡倾斜反射可能代表未受扰动的海岸风成沙的前积层。研究表明探地雷达是一种可靠、快速和经济的地球物理方法,在砂砾质海岸可产生高质量、高分辨率和连续的反射剖面,值得加以推广。  相似文献   

大别山造山带前陆深地震反射剖面   总被引：18，自引：0，他引：18       下载免费PDF全文

董树文 高锐李秋生  刘晓春钱桂华黄东定  匡朝阳李三忠管烨  白金贺日政  李朋武 《地质学报》2005,79(5):595-601

在大别山南部和扬子地块前陆实施的深地震反射剖面(140 km)揭示出大别山造山带前陆地壳的精细结构。总体北倾的地壳内部结构与向北缓倾的叠瓦状莫霍面反射揭示出扬子陆块向北俯冲的行迹。莫霍面向北插入大别山造山带下与南大别山地壳内南倾反射震相叠置,构成交叉反射图像,刻画出扬子前陆与大别山造山带的碰撞构造面貌。  相似文献