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黄河三角洲地区浅层沉积序列及构造沉降特征 总被引:3,自引:0,他引:3
在整个黄河三角洲地区和莱洲湾南岸晚更新世以来经历了海陆相沉积的频繁交替,本文通过古地磁和14C测年资料对不同钻孔的晚更新世地层进行了精确的年代对比,揭示了不同时期的沉积序列。并通过27口钻井的联合对比剖面,揭示出本区晚更新世以来的新构造运动表现为二凹夹一隆的构造特征,对黄河三角洲发育位置和沉降特征有强烈的控制作用。 相似文献
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Papadimitriou P. Voulgaris N. Kassaras I. Kaviris G. Delibasis N. Makropoulos K. 《Natural Hazards》2002,27(1-2):15-33
On 7 September 1999 at 11:56 GMT a destructive earthquake (Mw = 6.0) occurred close to Athens (Greece). The rupture process is examined using data from the Cornet local permanent network, as well as teleseismic recordings. Data recorded by a temporary seismological network were analyzed to study the aftershock sequence. The mainshock was relocated at 38.105°N, 23.565°E, about 20 km northwest of Athens. Four foreshocks were also relocated close to the mainshock. The modeling of teleseismic P and SH waves provides a well-constrained focal mechanism of the mainshock (strike = 105°, dip = 55° and rake = -80°) at a depth of 8 km and a seismic moment M0 = 1.01025 dyn·cm. The obtained fault plane solution represents normal faulting indicating an almost north-south extension. More than 3500 aftershocks were located, 1813 of which present RMS < 0.1 s and ERH, ERZ < 1.0 km. Two main clusters were distinguished, while the depth distribution is concentrated between 2 and 11 km. Over 1000 fault plane solutions of aftershocks were constrained, the majority of which also correspond to N–S extension. No surface breaks were observed but the fault plane solution of the mainshock is in agreement with the tectonics of the area and with the focal mechanisms obtained by aftershocks. The hypocenter of the mainshock is located on the deep western edge of the fault plane. The relocated epicenter coincides with the fringe that represents the highest deformation observed on the differential interferometric image. The calculated source duration is 5 sec, while the estimated dimensions of the fault are 15 km length and 10 km width. The source process is characterized by unilateral eastward rupture propagation, towards the city of Athens. An evident stop phase observed in the recordings of the Cornet local stations is interpreted as a barrier caused by the Aegaleo Mountain. 相似文献
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T. Geisler 《Physics and Chemistry of Minerals》2002,29(6):420-429
Raman spectroscopy and the powder diffraction technique have been used to monitor the recovery process of two partially metamict
zircons (2.6 and 4.8 × 1018
α-decays g−1) from Sri Lanka during a series of isothermal annealing experiments in the temperature range from 870 to 1622 K. These experiments
show for the first time that structural recovery in partially metamict zircon proceeds via three distinct recovery stages,
each of which occurs within a distinct time-temperature regime. Whereas the first two stages have previously been recognized
(recovery of damaged crystalline remnants and epitaxial recrystallization), the third stage has not yet been identified as
a single activated process. It is suggested that anisotropic defect annealing during the first stage at low temperatures,
where the structure recovers preferentially along the a(b) plane, produces a geometrical situation where large structural rearrangements are necessary to remove the remaining defects
inside the crystalline material. This situation is approximately reached when the amorphous domains start to recrystallize.
The reason for anisotropic annealing can be found in a different connectivity between polyhedral linkages in both directions
of the zircon lattice. High apparent activation energies, in the range of 6.4 to 7.9 eV, were determined for the third recovery
stage from the Raman data, which are interpreted to reflect large structural rearrangements (i.e. polyhedral tilting) associated
with the final recovery of the c axis. This explains the occurrence of a distinct recrystallization stage without defect annealing. Finally, it should be
mentioned that the first recovery stage is not necessarily expected to occur in less damaged zircon crystals (<∼2 × 1018
α-decays g−1), since less stable defects along the basal plane might have already been self-annealed during radiation damage accumulation
under ambient temperatures.
Received: 6 September 2001 / Accepted: 25 February 2002 相似文献
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圆弧状沉积盆地与软土单覆盖层出平面地表运动对比 总被引:2,自引:0,他引:2
采用解析方法,通过圆弧状沉积盆地与同样参数的软土均匀单覆盖层的对比,研究沉积盆地对平面SH波二维散射效应和其出平面地表运动。数值对比结果表明:(1)波垂直入射时盆地中央地表位移幅值反应,其随频率变化形式与软土单覆盖层的地表运动有较强的对应性,且此时单覆盖层地表位移幅值为其下降;(2)盆地的二维散射效应特点显著波的汇聚作用使盆地中的地表运动显著放大,总体上较软土单覆盖层的地表位移幅值要大,其频域内的最大反应则明显大于单覆盖层情况,但最大反应在盆地表面出现的位置依赖于入射波角度、盆地深宽比和盆地的软硬程度;(3)沉积盆地中地表位移运动有强烈扭转效应,且随盆地变软和入射波频率增高而增强。 相似文献
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大开间小型混凝土砌块10层模型房屋抗震性能试验研究(Ⅰ) 总被引:8,自引:3,他引:8
我国抗震设计规范(GB50011-2001)规定在6、7、8度区,混凝土小砌块结构分别可以建七、六、五层。由于混凝土小砌块结构的最大优势在于10-20层(与混凝土框架或框架剪力墙结构比)。本文按1/4比例制作了10层混凝土小砌块结构模型,按7度设防要求实施构造措施,通过振动台试验研究模型结构的抗震性能。结果表明,模型结构完全能够满足在7度区“小震不坏,大震不倒”的要求。圈梁、构造柱以及水平拉结筋构成的约束体系抗震作用是明显的。试验利用砌块的非注芯孔灌注铁砂来模拟墙体出平面动力效应。在本模型的构造措施下,平出面反应不对结构破坏起控制作用。 相似文献
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