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Based on Single-Link Cluster (SLC) analysis,a new method to identify the foreshocks andaftershocks of a strong shock from the earthquake catalogue and then to form a sequencecatalogue has been proposed in this paper.In the SLC frame,there are many chains formedby links with lengths shorter than or equal to the characteristic length Lc.It is defined thatwhen some of these chains connect with a strong shock,the seismic events on such chainsfirm a sequence with the strong shock.In this sequence,the strong shock is the main shock;the events preceding the main shock are foreshocks and those following the main shock areaftershocks.By using this method,the foreshocks and aftershocks associated with the M_s7.4Haicheng earthquake and with the strong shocks of M_s≥6.0 in the top area of Kunlun-AltunArc were identified and sequence catalogues for these strong shocks were set up. 相似文献
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西南印度洋中脊表层沉积物非碳酸盐组分的粒度特征及其地质意义 总被引:1,自引:0,他引:1
The carbonate-free fraction of 20 surface sediments collected from the ultraslow-spreading Southwest Indian Ridge(SWIR) was studied by grain size analysis and mineralogical analysis with X-ray powder diffraction(XRD),stereo microscopy and scanning electron microscopy(SEM). The characteristics of the carbonate-free fraction of the sediments were obtained, and related influential factors were discussed. The results show that the mean grain size of this fraction is in 1.96Φ–8.19Φ, with poorly sorting and unimodal, bimodal or irregular bimodal distribution patterns. Four grain size end members of the fraction are derived with the End Member Model method. The finest end member EM1 shows a significant contribution of terrigenous materials of the aeolian input and sediment carried by the bottom current. End member EM2 with medium size mainly reflects sediment of a siliceous bioclast origin. EM3 and EM4 are interpreted as representing the coarser volcanic materials related to bedrock weathering or volcanic activities. Multi-provenance is the dominant factor controlling the grain size pattern of the carbonate-free fraction of the sediments in that area. In addition, sediment transport processes such as the bottom current and wind are the minor factors that influence the grain size distribution of the carbonate-free fraction sediments. 相似文献
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西秦岭北缘构造带是青藏高原东北缘的主要构造边界之一,北缘断层及其所控制的新生代沉积盆地是青藏高原东北缘新生代盆—山格局演化、高原扩展隆升与变形的地质记录。因此,西秦岭北缘构造带的断裂构造和断裂控制的沉积盆地研究对于理解青藏高原构造系统形成和高原隆升过程都具有重要的科学意义。本文通过对西秦岭北缘新生代盆地的南部边界断层F1断层结构分带、断层岩类型、几何学—运动学特征分析,获得如下认识:1)F1断层总体走向为290°~300°,倾向北北东,倾角60°~80°,发育近百米宽的由韧性、韧脆性和脆性断层岩等组成的结构复杂的断层带;2)构造分析揭示了F1断层至少经历了 3期构造变形事件,第一期为韧性—韧脆性伸展正断层作用,第二期为脆性高角度挤压逆冲断层作用,第三期为近直立的脆性斜向左旋走滑作用;3)该断层近百米宽的断层带内形成于不同构造层次的韧性、韧脆性、脆性等变形现象叠加交织出现在现今地壳浅表层次,说明该断层带经历了从早期较深层次韧性变形域逐渐抬升而进入晚期较浅层次的脆韧性变形域到现今的脆性变形域的韧—脆性变形机制转换;4)根据F1断层对西秦岭北缘渐新统—中新统漳县含盐红层盆地的空间构造配置、控制和改造以及新生代区域构造变形演化历史分析,认为第一期韧性—韧脆性伸展正断层作用与渐新世—中新世断陷盆地形成相匹配,活动时代为晚渐新世—晚中新世;第二期脆性高角度挤压逆冲作用与渐新世—中新世地层翘起、褶皱和底部抬升剥蚀及上新世磨拉石盆地充填相对应,活动时代应该始于中新世末期或上新世早期,持续至第四纪早期;第三期斜向左旋走滑则与西秦岭北缘断层带第四纪以来广泛发育的左旋走滑作用相对应。综上所述,西秦岭北缘新生代漳县盆地南部边界断层F1,虽然仅是北缘构造带中一条断层,但作为构造敏感带,其多期变形历史应该代表了青藏高原东北缘新生代以来的构造变形演化及构造体制转换过程。如果这一新生代沉积盆地边界断层F1在渐新世—中新世一直处于伸展正断作用,那么西秦岭北缘在这个阶段应该处于地壳伸展拉张状态,渐新世—中新世漳县盆地只能是伸展断陷盆地而不可能是挤压挠曲前陆盆地或压陷盆地。因此,我们认为印度—欧亚板块碰撞汇聚产生的构造挤压缩短和地壳隆升效应在中新世尚未波及到西秦岭北缘区域。F1断层在中新世末—上新世初的构造反转挤压冲断和上新世具有再生前陆磨拉石堆积出现才标志着西秦岭北缘卷入青藏高原挤压构造动力学系统。 相似文献
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LIU Bin LIU Jianzhong ZHANG Guangliang LING Zongcheng ZHANG Jiang HE Zhiping YANG Benyong ZOU Yongliao 《中国地球化学学报》2014,33(1):86-94
In 2013, Chang'E-3 program will develop lunar mineral resources in-situ detection. A Visible and Near-infrared Imaging Spectrometer (VNIS) has been selected as one payload of CE-3 lunar rover to achieve this goal. It is critical and urgent to evaluate VNIS' spectrum data quality and validate quantification methods for mineral composition before its launch. Ground validation experiment of VNIS was carried out to complete the two goals, by simulating CE-3 lunar rover's detection environment on lunar surface in the laboratory. Based on the hyperspectral reflectance data derived, Correlation Analysis and Partial Least Square (CA-PLS) algorithm is applied to predict abundance of four lunar typical minerals (pyroxene, plagioclase, ilmenite and olivine) in their mixture. We firstly selected a set of VNIS' spectral parameters which highly correlated with minerals' abundance by correlation analysis (CA), and then stepwise regression method was used to find out spectral parameters which make the largest contri- butions to the mineral contents. At last, functions were derived to link minerals' abundance and spectral parameters by partial least square (PLS) algorithm. Not considering the effect of maturity, agglutinate and Fe~, we found that there are wonderful correlations between these four minerals and VNIS' spectral parameters, e.g. the abundance of pyroxene correlates positively with the mixture's absorption depth, the value of absorption depth added as the in- creasing of pyroxene's abundance. But the abundance of plagioclase correlates negatively with the spectral parame- ters of band ratio, the value of band ratio would decrease when the abundance of plagioclase increased. Similar to plagioclase, the abundance of ilmenite and olivine has a negative correlation with the mixture's reflectance data, if the abundance of ilmenite or olivine increase, the reflectance values of the mixture will decrease. Through model validation, better estimates of pyroxene, plagioclase and ilmenite's abundances are given. It is concluded that VNIS has the capability to be applied on lunar minerals' identification, and CA-PLS algorithm has the potential to be used on lunar surface's in-situ detection for minerals' abundance prediction. 相似文献
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分析合肥地震台钻孔体应变观测资料干扰因素及特征,发现水位和气压等因素对TJ-Ⅱ型钻孔应变仪影响显著.在该地震台观测优化改造期间,钻孔体应变受到临近钻孔灌水的影响,而降雨和灌水导致的水位变化,对体应变干扰程度不同. 相似文献
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