Single-Link Cluster Method to Identify Foreshocks and Aftershocks

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.     

Study of Influence of Regional Geodynamic Background on Strata Behaviors in China's Tongxin Mine

Strata behaviors are mainly affected by regional geodynamic background. The influence of rock mass stress and energy distribution on strata behaviors in the Tongxin mine is studied in terms of regional tectonic movement, seismic activity and tectonic stress field. The results show that the extrusion lifting movement of Kouquan fault adjacent to the Tongxin mine results in the stress concentration in the rock of the Carboniferous coal bed and accumulation of a large amount of elastic energy and forms structural background of Tongxin mine. Due to various seismic activities in the mine area, the strain energy is known to reach much higher levels, up to 0.5×10⁸ J^1/2. Since the stratigraphic structure is sensitive to the mining operation, the strain energy could cause strong strata behaviors. A special geological structure model of the Tongxin mine is established based on the geodynamic division method. The distribution of regional structure stress field is determined by the rock mass stress analysis system. Based on this model, Tongxin mine is divided into five areas with high stress, eight areas with low stress and eight areas with gradient stress. The strong strata behaviors mostly occur in high stress areas. These results could provide guidance to predict the strength of regional or mine pressure and control strata behavior in different areas.     

Detrital Zircon Dating of Meso- and Neoproterozoic Rocks in North China and Its Implications

New dates from Meso- and Neoproterozoic strata contribute to the recently defined Precambrian stratigraphical timescale of China agreed by the Subcommission on the Precambrian System, and the National Commission on Stratigraphy of China on Nov. 24, 2009. First, the age range of the Changcheng System, including the Changzhougou, Chuanlinggou, Tuanshanzi and Dahongyu formations has been constrained to 1.8–1.6 Ga. Second, the Jixian System including the Gaoyuzhuang, Yangzhuang, Wumishan, Hongshuizhuang and Tieling formations has been constrained to 1.6–1.4 Ga. Third, an as-yet unnamed (undefined) system (1.4–1.0 Ga) is only developed in the Xiamaling Formation at the Jixian section, Tianjing. Fourth, the Qingbaikou System, including the Luotuoling and Jing’eryu formations has been constrained to 1.0–0.78 Ga. Fifth, the Nanhuan System ranges between 780–635 Ma, and the Sinian System is within 635–542 Ma. However, according to a series of SHRIMP U-Pb dates from the late Precambrian in the Jiangnan Orogen Belt in South China Platform, the constrained strata will be redefined as in the upper part of the Qingbaikou System. To aid global geodynamics, it is useful to denote a late Precambrian section with unified, precise and high-precision chronological dating; this is here defined in North China Block and Jiaoliao-Korean Block. However, the Neoproterozoic Qingbaikou study in North China will be influence in whole Meso- and Neoproterozoic in the Jiangnan Orogenic Belt in between the Yangtze Block and the Cathaysia Block in South China.     

廊固凹陷近岸水下扇特征及控制因素

通过对廊固凹陷18口井541 m岩心的系统观察、156口井测井序列的建立、1km×1 km三维地震测网密度的地震相识别,分析了该沉积体系的相带展布特征。该砂砾岩层总体趋势为向上厚度减薄、层数减少,共识别出5期扇体,多呈条带状沿大兴断层断面分布,每期之间发育稳定的暗色泥岩段。该近岸水下扇的形成受3级层序、大兴断层、古构造、古气候、古地形以及物源供给等多种因素的控制。3级层序的发育特点、大兴断层的分段活动以及特殊的物源供给背景因素的匹配对近岸水下扇形成起到决定性作用。2~3期扇体扇中分布范围广,储集条件好,是凹陷下一步开发工作的有利目标。     

珊溪水库地震台阵建设

为更好地对珊溪水库地震震群进行监测和分析,浙江省地震局自2006年开始建设珊溪水库地震台阵.介绍了该环形小孔径台阵的勘选和建设过程,并结合2次地震震群活动的监测数据,展示了该台阵对地区性地震活动监测的效果.     

高台测震新旧台基记录地震及震相特征差异性对比分析

使用相同带宽、同类型地震计BBVS-120观测记录数据,对高台地震台新旧观测山洞的台基环境噪声、地震监测能力及震相记录特征进行对比分析,结果表明,高台测震新山洞的地震监测水平优于旧山洞,部分地区新山洞对于核面反射波的记录更加清晰。     

蒙古塔木察格盆地塔南凹陷下白垩统层序结构类型、控制因素与层序发育模式

利用录井及地震反射资料,采用层序地层学原理对蒙古塔木察格盆地塔南凹陷下白垩统地层层序进行了划分和对比,划分出了4个三级层序（SQ1-SQ4）。在此基础上,结合盆地的构造演化特点,研究了层序结构特征,划分了层序类型,其中,SQ1和SQ2为初始裂谷期湖泊层序,SQ3为裂谷深陷期层序,SQ4为裂谷后过渡层序。层序的结构主要受构造沉降方式控制,塔南凹陷不同时期构造沉降方式不同,形成了3种层序发育模式,即简单箕状斜坡模式、差异沉降构造反转模式、坳陷型层序发育模式,不同的层序发育模式,其地层岩性圈闭的发育和分布不同。     

山东埕岛东部东营组三角洲砂体地震预测技术

山东埕岛地区东营组是胜利油田近年来的一个勘探热点地区,资源潜力巨大.其主要发育河流和三角洲沉积体系,但砂体地震反射特征复杂,横向变化快,储层识别描述难度较大.通过建立全区高分辨率层序地层格架,在等时层序格架的基础上,开展储层描述.湖相沉积与三角洲相沉积在沉积物特征和地震响应上都具有较大差异,通过对已钻井的岩心、测井和录井等资料的分析,结合地震属性和地震相等宏观描述方法,在湖相沉积的背景之下刻画出三角洲的整体展布形态.在此基础上,针对三角洲主体区地震反射较弱、砂泥岩速度差异较小的特点,利用地震波形识别技术,采用6种参数对波形进行描述,得出12种波形分类,分别对应4种主要沉积微相.最终利用神经网络方法在平面上进行沉积微相的识别和刻画,取得了较好的效果.     

Downward migration of seismic activity prior to some great shallow earthquakes in Japanese subduction zones—a possible intermediateterm precursor

Before the 1944 Tonankai earthquake along the Nankai Trough, seismic activity increased in the shallow depths, and then the activity gradually migrated downwards. When it reached its limit (a depth of approximatelty 70 km), the main shock occurred. Several deep earthquakes, including one ofM5.3, occurred several months prior to the Tonankai earthquake. A similar downward migration pattern also can be recognized regarding the 1952 Tokachi-oki earthquake. In this case the deepest earthquakes reached about 400 km. This may be one of the intermediate-term precursory phenomena of great thrusttype earthquakes in subduction zones. Recent observations in the Tokai district along the Suruga Trough, where a large earthquake is expected to occur in the future, suggest a similar downward migration pattern in the land area.     

井地地震CT成像数值模拟研究与应用

由井地地震CT成像原理决定,其在提高生产效率、降低生产成本和扩大勘察范围上具有突出优势.本文针对井地观测系统,重点通过对ART和SIRT重建方法进行数值模拟对比研究,分析得出二者在井地地震CT应用中的优缺点及适用条件,提出了如何提高影响成像质量的射线分布密度、均匀性和正交性.最后选择收敛快速稳定的SIRT算法应用于实际,取得良好的生产效果,很好的验证了井地CT成像技术的正确性,可行性和实用性.