Seismotectonic database of Turkey     

Tamer Y. Duman  Tolga Çan  Ömer Emre  F. Tuba Kadirioğlu  Nilay Başarır Baştürk  Tuğbay Kılıç  Selim Arslan  Selim Özalp  Recai F. Kartal  Doğan Kalafat  Ferdane Karakaya  Tuba Eroğlu Azak  Nurcan M. Özel  Semih Ergintav  Sinan Akkar  Yıldız Altınok  Senem Tekin  Ayhan Cingöz  A. İhsan Kurt 《Bulletin of Earthquake Engineering》2018,16(8):3277-3316

Turkey is located in one of the most seismically active regions in the world. Characterizing seismic source zones in this region requires evaluation and integration of geological, geophysical, seismological and geodetical data. This first seismotectonic database for Turkey presented herein was prepared, under the framework of the National Earthquake Strategy and Action Plan—2023. The geographic information system (GIS)-based database includes maps of active faults, catalogues of instrumental and historical earthquakes, moment tensor solutions and data on crustal thickness. On the basis of these data, 18 major seismotectonic zones were delineated for Turkey and the surrounding region. The compilation and storage of the seismotectonic data sets in a digital GIS will allow analyses and systematic updates as new data accrete over time.  相似文献   

Internal structure of intense collisional bedload transport     

Václav Matoušek  Štĕpán Zrostlík  Luigi Fraccarollo  Anna Prati  Michele Larcher 《地球表面变化过程与地形》2019,44(11):2285-2296

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A Paleozoic age for the Tunnunik impact structure     

Camille Lepaulard  Jrme Gattacceca  Nicholas Swanson‐Hysell  Yoann Quesnel  Franois Demory  Gordon R. Osinski 《Meteoritics & planetary science》2019,54(4):740-751

We report paleomagnetic directions from the target rocks of the Tunnunik impact structure, as well as from lithic impact breccia dikes that formed during the impact event. The target sedimentary rocks have been remagnetized after impact‐related tilting during a reverse polarity interval. Their magnetization is unblocked up to 350 °C. The diabase dikes intruding into these sediments retained their original magnetization which unblocks above 400 °C. The impact breccia records a paleomagnetic direction similar to that of the overprints in the target sedimentary rocks. The comparison of the resulting virtual geomagnetic pole for the Tunnunik impact structure with the apparent polar wander path for Laurentia combined with biostratigraphic constraints from the target sedimentary rocks is most consistent with an impact age in the Late Ordovician or Silurian, around 430–450 Ma, soon after the deposition of the youngest impacted sedimentary rocks. Our results from the overprinted sedimentary rocks and diabase dikes imply that the postimpact temperature of the studied rocks was about 350 °C.  相似文献   

Hydrothermally enhanced magnetization at the center of the Haughton impact structure?          下载免费PDF全文

W. Zylberman  Y. Quesnel  P. Rochette  G. R. Osinski  C. Marion  J. Gattacceca 《Meteoritics & planetary science》2017,52(10):2147-2165

Haughton is a ~24 Myr old midsize (apparent diameter 23 km) complex impact structure located on Devon Island in Nunavut, Canada. The center of the structure shows a negative gravity anomaly of ?12 mGal coupled to a localized positive magnetic field anomaly of ~900 nT. A field expedition in 2013 led to the acquisition of new ground magnetic field mapping and electrical resistivity data sets, as well as the first subsurface drill cores down to 13 m depth at the top of the magnetic field anomaly. Petrography, rock magnetic, and petrophysical measurements were performed on the cores and revealed two different types of clast‐rich polymict impactites: (1) a white hydrothermally altered impact melt rock, not previously observed at Haughton, and (2) a gray impact melt rock with no macroscopic sign of alteration. In the altered core, gypsum is present in macroscopic veins and in the form of intergranular selenite associated with colored and zoned carbonate clasts. This altered core has a natural remanent magnetization (NRM) four to five times higher than materials from the other core but the same magnetic susceptibility. Their magnetization is still higher than the surrounding crater‐fill impact melt rocks. X‐ray fluorescence data indicate a similar proportion of iron‐rich phases in both cores and an enrichment in silicates within the altered core. In addition, alternating‐field demagnetization results show that one main process remagnetized the rocks. These results support the hypothesis that intense and possibly localized post‐impact hydrothermal alteration enhanced the magnetization of the clast‐rich impact melt rocks by crystallization of magnetite within the center of the Haughton impact structure. Subsequent erosion was followed by in situ concentration in the subsurface leading to large magnetic gradient on surface.  相似文献   

Predicting the occurrence of sand banks in the North Sea     

H. Henriët van der Veen  Suzanne M. J. H. Hulscher 《Ocean Dynamics》2009,59(5):689-696

Sand banks have a wavelength between 1 and 10 km, and they are up to several tens of meters high. Also, sand banks may have an impact on large-scale human activities that take place in the North Sea like sand mining, shipping, offshore wind farms, etc. Therefore, it is important to know where sand banks occur and what their natural behavior is. Here, we use an idealized model to predict the occurrence of sand banks in the North Sea. The aim of the paper is to research to what extent the model is able to predict the occurrence of sand banks in the North Sea. We apply a sensitivity analysis to optimize the model results for a North Sea environment. The results show that the model correctly predicts whether or not sand banks occur for two thirds of the North Sea area.  相似文献   

The effects of antecedent moisture conditions on the relationship of hydrology to hydrochemistry in a small forested watershed     

Pascale M. Biron  Andr G. Roy  Franois Courschesne  William H. Hendershot  Benoît Ct  Jim Fyles 《水文研究》1999,13(11):1541-1555

The relationship between stream discharge and the concentration of different solutes reflects the hydrological processes occurring in a catchment, but is also strongly affected by antecedent moisture conditions. In this study, the effects of antecedent conditions were examined for a small forested watershed near Montréal (Québec) by comparing data from sequences of fall events for two years of contrasting antecedent moisture conditions. The relationship between discharge and stream water chemistry was also quantified using cross‐correlation analysis. Results show that concentrations of dissolved organic carbon, nitrate and calcium increased during storm events with dry antecedent conditions but that the relationships were weaker under wet conditions. For both years, concentrations of sulfate, silicon and sodium and the pH were negatively correlated with discharge (cross‐correlations from −0·20 to −0·53). With dry antecedent conditions, there was a general decrease in the concentration of all solutes with time, whereas concentrations remained at about the same level under wet conditions. The concentration–discharge relationships for sulfate shifted frequently from higher concentrations during the rising limb to higher concentrations during the falling limb from one event to another as a result of changing antecedent conditions. Although the contrast in antecedent moisture conditions between the two years was moderate in comparison with that reported in other studies (25% dryer than average in 1995 and 12% wetter than average in 1996), the hydrochemistry of the stream was markedly different. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Olivine chemistry from Cameroon: evidence of carbonate metasomatism along the ocean-continental boundary of the Cameroon volcanic line     

Ngwa  Caroline N.  Shu  Bless N.  Mbassa  Benoît J.  Aka  Festus T.  Wokwenmendam  Pauline N. 《Mineralogy and Petrology》2020,114(1):57-70

Mineralogy and Petrology - We report olivine chemistry in basaltic rocks from the Mt. Cameroon Volcanic area, which is used as a proxy to understand mantle and early igneous processes along the...  相似文献   

北京石花洞石笋500年来的δ￣（13）C记录与古气候变化及大气CO2浓度变化的关系   总被引：9，自引：1，他引：8  

李红春  顾德隆  Lowell D. Stott  袁道先  陈文寄  李铁英 《中国岩溶》1997,16(4):285-295

通过对采自北京石花洞石笋近５００年来分辨率为３～５年的δ１３Ｃ记录的研究,我们发现水动力条件的改变和近代大气ＣＯ２浓度的改变均对石笋的δ１３Ｃ值有影响,当气候湿润,降雨量增加时,洞穴包气带水的下渗速度加快,在石灰岩裂隙中滞留的时间缩短,ＣａＣＯ３的溶解量减少,造成渗出δ１３Ｃ水的值变轻。包气带水的补给速度增加,也可能使得溶液的ＣＯ２分压降低,造成石灰岩ＣａＣＯ３溶解减少。另外,洞内滴水和渗出水中ＣＯ２的逸出量与供水速度呈反比。滴水速度加快,ＣＯ２逸出量相对降低,沉淀出来的ＣａＣＯ３的δ１３Ｃ值偏轻。通过与δ１８Ｏ记录的对比,δ１３Ｃ记录也反映３０～４０年降雨量变化的周期,为这一地区夏风变化的规律提供佐证。近５０年来的δ１３Ｃ记录,反映了人类活动造成大气ＣＯ２浓度升高的现象。从１９４０年到现今,石笋的δ１３Ｃ值从－６．７‰降低到－８．１‰,降低速率每年为－０．０２８‰,直接反映了这一时期大气ＣＯ２的δ１３Ｃ值的变化。这一结果与其它研究相吻合。利用精细的、分辨率高达几年的δ１３Ｃ记录可以为岩溶作用与碳循环的研究提供有效手段。   相似文献   

Saraçköy Volcanic Suite: implications for the subductional phase of arc evolution in the Galatean Arc Complex,Ankara, Turkey     

Ali&#x; Koyi&#x;i&#x;t  John Alan Winchester  Erdi&#x;n Bozkurt  Grenville Holland 《Geological Journal》2003,38(1):1-14

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Influence of root characteristics and soil variables on the uprooting mechanics of Avena sativa and Medicago sativa seedlings          下载免费PDF全文

Katharina Edmaier  Benoît Crouzy  Roland Ennos  Paolo Burlando  Paolo Perona 《地球表面变化过程与地形》2014,39(10):1354-1364

The success of seedlings and rejuvenated woody debris growing on river bedforms depends on the resistance to uprooting by flow provided by their simple root architecture. Avena sativa and Medicago sativa seedlings were used in flume experiments as prototypes for juvenile riparian plants. Very little is known about the magnitude of root anchoring forces and the role of secondary roots of such simple root systems. We performed 1550 vertical uprooting experiments on Avena sativa and Medicago sativa seedlings grown in quartz sand. Seedlings were pulled up by direct traction using a wheel driven by a computer‐controlled motor and the force was recorded. Roots were scanned and architectural parameters (root length and number of roots) determined. Uprooting force and work (the integral of the applied force times the distance over which it is applied) were then related to root architecture and soil variables. Resistance to uprooting increased with decreasing sediment size and sediment moisture content. The initial response of the root–soil system to uprooting showed linear elastic behaviour with modulus increasing with plant age. While the maximum uprooting force was found to increase linearly with total root length and be mainly dependent on the length of the main root, uprooting work followed a power law and has to be related to the whole root system. Thus, for the young plants we considered, secondary roots are responsible for the ability to withstand environmental disturbances in terms of duration rather than magnitude. This distinction between primary and secondary roots can be of crucial importance for seedlings of riparian species germinating on river bars and islands where inundation is a main cause of mortality. Beyond clarifying the biomechanical role of soil and root variables, the uprooting statistics obtained are useful in interpreting and designing ecomorphodynamic flume experiments. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献