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1.
快速确定断层破裂特征是烈度速报的一项重要技术,断层破裂特征可为烈度速报提供震源模型,提升烈度速报准确性。通过汶川地震加速度记录,提出一种快速计算震源破裂参数的方法。 假定断层为线源模型,以一定间距将断层离散化为若干子源,以震中为不动点,通过旋转获得所有断层可能的走向,通过每次移动一个子源,获得断层所有可能的破裂方式,将二者结合即可给出断层所有可能的空间分布;计算每种断层空间分布与每个台站的断层距,利用加速度记录峰值和断层距统计回归衰减关系,分析每个衰减关系的拟合残差,残差最小拟合效果最好的衰减关系所对应断层参数,能够对该次地震的地震动场有最合理的解释,也最有可能是实际地震中的断层空间分布。  相似文献   
2.
陈建业  杨晓松 《地震地质》2014,36(2):368-379
断层岩的粒度分布包含岩石破裂机制、摩擦性质和地震能量分配等重要信息。筛分-称重和激光测量是分析断层岩三维粒度的2种有效方法,但每一种方法的测量范围仅有3个量级,难以全面反映断层岩的粒度分布特征。利用上述2种方法对汶川地震断层滑动带上的断层岩(简称断层岩)的粒度分布进行了测量,粒径测量范围从0.2μm至16mm,跨度达到5个数量级。结果显示:1)存在临界粒径dc(0.95~1.90μm)。粒度大于和小于dc的颗粒满足不同的颗粒数(Nd)-粒径(d)分布关系,表明该断层岩的粒径分布不具有自相似性特征。2)利用粒度大于dc的颗粒计算出的分形维数与断层岩类型有很好的相关性,即断层带边缘的角砾岩的平均分形维数为2.6,核部压碎角砾岩的平均分形维数约为3.0,中心断层泥的分形维数约为3.5。粒径小于dc的颗粒的分形维数为1.7~2.1。分形维数的突变反映出断层破裂机制的复杂性,即在不同的粒度域,岩石的破裂机制不尽相同。3)依据粒度分析结果,估算出汶川地震断层泥的单位破裂能(Es)为0.63MJ/m2。  相似文献   
3.
以芦山、汶川地震震中为中心,选择了8个井点,对2个地震引起的井水位同震变化进行了比较,重点分析了3口同震变化反向的井点,即重庆的荣昌华江井、北碚柳荫井和四川的泸沽湖井。为使对比研究结果可靠,进一步收集了2011年3月11日日本9.0级地震、2012年4月11日苏门答腊北部海域8.6级地震引起的井水位同震变化资料。对汶川、芦山地震引起的同震体应变的计算结果显示:汶川地震时,荣昌华江井、北碚柳荫井和泸沽湖井水位同震变化与井点位置处的同震体应变一致,即位于同震体应变压缩区的井水位上升,位于体应变膨胀区的井水位下降;芦山地震时,3口井的水位同震变化与同震体应变不一致,表现出与日本、苏门答腊地震时相似的同震变化特征。  相似文献   
4.
In 2010, a 500-km-long wide-angle reflection/refraction seismic profile was completed, running northwest from the central Sichuan Basin. This profile orthogonally crosses the meizoseismal area of great Wenchuan earthquake of 12 May 2008, which occurred in the central part of the Longmenshan. The profile also passes through the northwestern Sichuan Plateau, along which a new deep seismic sounding observation system was set up that was much improved over previous datasets and enabled abundant observations to be recorded. Seismic wave phase records that reflect the structural characteristics of different tectonic blocks, especially the complicated phase features associated with the Wenchuan earthquake, were calculated and analyzed in detail. A 2D crustal P-wave velocity model for the orogenic belt in the central Longmenshan and its margins was determined, and crustal structure differences between the stable Sichuan Basin and the thickened northwestern Sichuan Plateau were characterized. Lithological variations within the upper and lower crust in the interior of the plateau, especially a great velocity decrease and plastic rheological properties associated with strong lithologic weakening in lower crust, were detected. From west to east in the lower crust beneath the orogenic belt lying between the Sichuan Basin and the northwestern Sichuan Plateau, a giant shovel-like upwelling is observed that dips gently in the lower part and at higher angles in the upper part; this is inferred to be related to the fault systems in the central Longmenshan. An upwelling in the upper-middle crust along the eastern margin of the orogenic belt is associated with steeply dipping thrusts that strongly uplift the upper crust and crystalline basement beneath a central fault system in the Longmenshan. The data, combined with an understanding of the regional tectonic stress field and previous geological results, enable a discussion of basin-and-range coupling, orogenic tectonics, the crustal fault system, and the seismogenic tectonic environment of the central Longmenshan along the eastern margin of the Qinghai-Tibet Plateau.  相似文献   
5.
The permeabilities of fault rocks from the rupture of Wenchuan earthquake were measured by using nitrogen gas and distilled water as pore fluids under the confining pressure ranging from 20 to 180 MPa at room temperature. Experimental results indicate that both gas and water permeabilities decrease with increasing confining pressure, described by power law relationship, i.e., b = 0.2×10–3kl–0.557. The water permeability is about one order less than gas permeability and also half order smaller than the permeability corrected by the Klinkenberg effect, so-called intrinsic permeability. The differences in the permeabilies imply that the reduction of effective pore size caused by the adhesion of water molecules to clay particle surface and water-swelling of expandable clay minerals contributes to lessening the water permeability besides the Klinkenberg effect. Hence, the liquid permeability of fault rocks cannot be deduced by gas permeability by the Klinkenberg correction reliably and accurately, and it is necessary to use liquid as pore media to measure their transport property directly.  相似文献   
6.
通过对比研究发现,2008 年汶川8. 0 级和2011 年日本9. 0 级地震时甘肃境内台站井水位和井水温同震效应特征有明显差异:汶川8. 0 级地震时,绝大部分井水位和井水温都记录到同震效应,且变化幅度比较大,持续时间比较长;相比而言,日本9. 0 级地震虽然释放的能量更大,但因震中距和震源方位的影响,只有部分井水位记录到明显的同震变化,井水温没有明显变化;两次地震时古浪观测站井水位都记录到井水位变化,但日本9. 0 级地震时的变化幅度大于汶川8. 0 级地震,这一现象值得深入研究。  相似文献   
7.
The MS8.0 Wenchuan earthquake caused a great deal of damage and collapse to engineering structures. Survey of disaster and engineering damage was made in detail by the authors and other researchers in the extreme earthquake disaster area. The paper makes an overview of the earthquake disaster status and damage phenomena which include brick-concrete buildings, frame structures, brick-wood structures, and timber frame residential buildings. Furthermore, the causes of the disaster and building damage phenomena are briefly discussed. In addition, some typical damage phenomena are specialized. According to the phenomena mentioned above, some feasible seismic measures are suggested for the development of buildings in future.  相似文献   
8.
Field investigations following the 2008 Wenchuan earthquake (Ms=8.0) identified 118 liquefaction sites nearly all of which are underlain by gravelly sediment in the Chengdu Plain and adjacent Mianyang area. Field studies, including core drilling, dynamic penetration tests (DPT), and multiple channel analysis of surface wave velocity tests (MASW) for measurement of shear wave velocities, reveal the following: (1) Sand boils and ground fissures, indicative of liquefaction, occurred across hundreds of square kilometers affecting 120 villages, 8 schools and 5 factories. (2) The Chengdu plain is underlain by sandy gravels ranging in thickness up to 540 m; loose upper layers within the gravels beds liquefied. (3) Mean grain sizes for gravelly layers that liquefied range from 1 mm to more than 30 mm. (4) Shear wave velocities in gravels that liquefied range up to 250 m/s. (5) A 50% probability curve, developed from logistic procedures, correctly bounds all but four data points for the 47 compiled Vs data.  相似文献   
9.
An YRY-4 type borehole strainmeter at Guza station on the southwest end of the Longmenshan fault zone recorded anomalous changes from time to time since about one year before the Wenchuan earthquake.The anomaly is characterized by steps and/or asymmetrical pulses of short-periods(minutes-hours).Among about one hundred stations over the mainland of China,only Guza,the nearest one to the seismic area,observed such changes.A self-check function of the strainmeter helps confirm the credibility of the observatio...  相似文献   
10.
Two types of changes in apparent resistivity (AR) have been linked to earthquake occurrences. This paper studies the changes and their causes, in detail with the ultimate purpose of developing and assessing a method of earthquake (EQ) prediction. The AR changes of the first type (CFT) are considered to be precursors related to earthquakes (EQs); these appear mostly in the medium-term period before EQs and in the short-term period preceding EQs. The changes of the second type (CST) are characterized by a tur...  相似文献   
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