High-Resolution Seismic Reflection Profiling of the Fenhe Fault in Taiyuan City

In this paper, we demonstrate the high-resolution seismic reflection data for a depth range of several hundred meters across the Fenhe fault in Taiyuan city, China. In combination with the relevant borehole logs, these data provide useful constraints on the accurate position, geometry and deformation rate of the fault, as well as the kinematics of recent fault motion. The highresolution seismic reflection profiling revealed that the western branch of the Fenhe fault is a high angle, eastward dipping, oblique-normal fault, and cutting up to the lower part of the Quaternary system. It was revealed that the top breaking point of this fault is at a depth of～70m below the ground surface. A borehole log across the Fenhe fault permitted us to infer that there are two high-angle, oppositely dipping, oblique-normal faults. The eastern branch lies beneath the eastern embankment of the Fenhe river, dipping to the west and cutting into the Holocene-late Pleistocene strata with a maximum vertical offset of～8m. Another borehole log across the northern segment of the Fen]he fault indicates that the western branch of this fault has cut into the Holocene-late Pleistocene strata with a maximum vertical offset of～6m. The above-mentioned data provide a minimum average Pieistocene-Holocene vertical slip rate of 0.06～0.08mm/a and a maximum average large-earthquake recurrence interval of 5.0～6.7ka for the Fenhe fault.     

An Effective Reservoir Parameter for Seismic Characterization of Organic Shale Reservoir

Sweet spots identification for unconventional shale reservoirs involves detection of organic-rich zones with abundant porosity. However, commonly used elastic attributes, such as P- and S-impedances, often show poor correlations with porosity and organic matter content separately and thus make the seismic characterization of sweet spots challenging. Based on an extensive analysis of worldwide laboratory database of core measurements, we find that P- and S-impedances exhibit much improved linear correlations with the sum of volume fraction of organic matter and porosity than the single parameter of organic matter volume fraction or porosity. Importantly, from the geological perspective, porosity in conjunction with organic matter content is also directly indicative of the total hydrocarbon content of shale resources plays. Consequently, we propose an effective reservoir parameter (ERP), the sum of volume fraction of organic matter and porosity, to bridge the gap between hydrocarbon accumulation and seismic measurements in organic shale reservoirs. ERP acts as the first-order factor in controlling the elastic properties as well as characterizing the hydrocarbon storage capacity of organic shale reservoirs. We also use rock physics modeling to demonstrate why there exists an improved linear correlation between elastic impedances and ERP. A case study in a shale gas reservoir illustrates that seismic-derived ERP can be effectively used to characterize the total gas content in place, which is also confirmed by the production well.     

High-Resolution Seismic Characterization of Shallow Gas Accumulations in the Southern Shelf of Marmara Sea,Turkey

High-resolution seismic survey was conducted to investigate acoustic characteristics of gassy sediments along the southern shelf of the Sea of Marmara. The acoustic turbidity zones outlined within the study area are generally below 2–9 m (2-10 ms TWT) the seafloor whilst this vertical distance varies between 9 and 21 m (10–25 ms TWT) for acoustic blanket type reflections. The gassy sediments cover an area of sea floor of about 45, 110, and 75 km² in front of Gönen River, Kocasu River, and Gemlik Bay, respectively. The gassy sediments in the center of Gemlik Bay exhibited an elliptical geometry similar to its basin while the others have deltaic forms in front of the rivers. The sea bottom and near surface sedimentary units are made-up of organic-rich sediments, mostly transported by the southern rivers. The gas observed in sediments is thought to be of biogenic origin, which may be caused by degradation of organic matter in the sediment.     

Application of Marine Seismic Profiling to a Ground Water Contamination Study, Aberdeen Proving Ground, Maryland

Continuous high-frequency marine seismic profiling was used to define the extent of geologic units in the offshore areas of J-Field, Aberdeen Proving Ground, Maryland, during March and April of 1988. J-Field is an area that was used by the U.S. Army for disposal of chemical warfare agents, munitions, and organic solvents from the 1950s through the 1970s. A major concern at this site is the subsurface migration of hazardous wastes into offshore areas and eventually into the Chesapeake Bay. A 150-foot (45.7 meter) deep paleochannel containing Pleistocene age fluvial and estuarine sediments was identified from boreholes constructed onshore. The paleochannel sediments consist of three lithic units. From bottom to top these units consist of gravel and sand, massive silty and sandy clay, and interbedded sand and clay. The seismic profiles were used to identify the extent of these units and map them in offshore areas. An accurate knowledge of the distribution of the geologic units in onshore and offshore areas is important to the investigation because the coarse-grained paleochannel sediments may provide a preferential flow path for contaminated ground water and the fine-grained sediments may impede the movement of contaminants into deeper aquifers.     

利用高频地震波检测混凝土构件完整性的方法

大型混凝土构件（如高层建筑基础的地梁,桩承台等）在施工过程中可能造成局部松散,空洞,蜂窝或离析等质量问题。为检测混凝土构件的的完整性,采用地震勘探方法中的地震映象法（又称地震共偏移距法）。通过在模拟裂缝,空洞模型上的试验,获得了存在异常体时,地震映象时间剖面的波形特征;测得偏移距,点距等参数变化时,对地震映象时间剖面的影响。模型实验和实测工作证明;在合理选择震源各种测量参数条件下,高频地震映象方法可有效检测混凝土构件完整怀,实现对混凝土构件质量新的监测。     

糯扎渡水库地区地震活动和震源参数研究

本文利用糯扎渡水库台网和景洪水库台网记录的地震波形反演震源谱, 计算了2011年1月至2014年3月糯扎渡水库附近143个1.0级以上地震的震源参数。 分析研究发现: ① 糯扎渡水库蓄水后, 库区内地震活动明显增强, 尤其是在水位上升3~4个月后; ② 水库开始蓄水后, 库区内地震震源深度变浅, 一段时间以后则与库区外的差别减小; ③ 地震拐角频率随地震矩增大而减小, 且蓄水以后, 库区内地震拐角频率的对数与地震矩的对数线性关系更明显; ④ 应力降、 视应力与地震矩存在正相关关系, 且相同地震矩时库区内的应力降与视应力低于蓄水前和库区外的地震应力降与视应力值; ⑤ 蓄水对库区内地震的影响可延伸至库底10 km深度处, 且在3~6 km深度内影响最大、 库区内外地震频度与视应力均值差异最显著。     

Seismic Detection and Characterization of the Altiplano-Puna Magma Body, Central Andes

— The Altiplano-Puna Volcanic Complex (APVC) in the central Andes is the product of an ignimbrite “flare-up” of world class proportions (de Silva, 1989). The region has been the site of large-scale silicic magmatism since 10 Ma, producing 10 major eruptive calderas and edifices, some of which are multiple-eruption resurgent complexes as large as the Yellowstone or Long Valley caldera. Seven PASSCAL broadband seismic stations were operated in the Bolivian portion of the APVC from October 1996 to September 1997 and recorded teleseismic earthquakes and local intermediate-depth events in the subducting Nazca plate. Both teleseismic and local receiver functions were used to delineate the lateral extent of a regionally pervasive ～20-km-deep, very low-velocity layer (VLVL) associated with the APVC. Data from several stations that sample different parts of the northern APVC show large amplitude Ps phases from a low-velocity layer with Vs ≤ 1.0 km/s and a thickness of ～1 km. We believe the crustal VLVL is a regional sill-like magma body, named the Altiplano–Puna magma body (APMB), and is associated with the source region of the Altiplano–Puna Volcanic Complex ignimbrites (Chmielowski et al., 1999).¶Large-amplitude P–SH conversions in both the teleseismic and local data appear to originate from the top of the APMB. Using the programs of Levin and Park (1998), we computed synthetic receiver functions for several models of simple layered anisotropic media. Upper-crustal, tilted-axis anisotropy involving both Vp and Vs can generate a “split Ps” phase that, in addition to the Ps phase from the bottom of a thin isotropic VLVL, produces an interference waveform that varies with backazimuth. We have forward modeled such an interference pattern at one station with an anisotropy of 15%–20% that dips 45° within a 20-km-thick upper crust. We develop a hypothesis that the crust above the “magma body” is characterized by a strong, tilted-axis, hexagonally symmetric anisotropy. We speculate that the anisotropy is due to aligned, fluid-filled cracks induced by a “normal-faulting” extensional strain field associated with the high elevations of the Andean Puna.     

Self-organized Fractal Seismicity of Reservoir Triggered Earthquakes in the Koyna-Warna Seismic Zone,Western India

— Analysis of the Koyna-Warna earthquake catalog (1968–1996) shows that on an average there is a positive correlation between the b value (decrease) and fractal dimensions (decrease in both D₂^s and D₂^t) of earthquake epicenters 0.5 and 2.5 years prior to 1973 (M5.2) and 1980 (M5.5) events, respectively, except a negative correlation for about five years (1988–1993) prior to the 1993/1994 sequence (M5.4). This positive correlation indicates a weaker clustering, or that the epicenters tend to fill the two-dimensional plane. While the origin of the negative correlation seems to be that during periods of large events (low b value), there is strong clustering around the main shock epicenter (high fractal dimension). Interestingly, during the last year (1995–1996) of the studied period both the b value and correlation dimensions rose significantly, suggesting that stress release occurs through increased levels of low magnitude and increasingly scattered seismicity, suggesting an increased risk of larger magnitude events. Incidentally, during 2000 three earthquakes of magnitude M 5.0, one earthquake of M 4.0, 45 earthquakes of magnitude M 3.0–3.9, and several thousand earthquakes of M < 3 have occurred in the region. Thus it can be inferred that at local scales the relationship yields both positive and negative correlation that appears to be controlled by different modes of failure within the active fault complex.Acknowledgement. The authors are grateful to Dr. B.K. Rastogi of NGRI for providing the catalog of Koyna earthquakes and for useful scientific discussions. The comments of Dr. I. G. Main have improved the quality of paper for which we extend to him our sincere thanks. One of the authors (AOM) thanks the Third World Academy of Science and the Council of Scientific and Industrial Research, India for the Postdoctoral Fellowship award under which this work was carried out.     

瀑布沟水库库区介质衰减、台站响应和震源参数研究

利用数字地震台网2007年1月到2011年12月记录到的瀑布沟水库及邻区地震波形资料,采用Atkinson方法计算了库区介质品质因子;并利用Moya方法计算了台站场地响应;在获得介质品质因子和台站场地响应的基础上联合反演计算了瀑布沟库区67次构造地震和208次爆破地震的震源波谱参数,同时讨论了它们的时空特征。结果表明：瀑布沟库区Q值与频率的关系为Q（f）=47.1*f0.92;各台站的场地响应随频率变化不大,场地响应均在1附近。     

瀑布沟水库库区介质衰减、台站响应和震源参数研究

利用数字地震台网2007年1月到2011年12月记录到的瀑布沟水库及邻区地震波形资料,采用Atkinson方法计算了库区介质品质因子;并利用Moya方法计算了台站场地响应;在获得介质品质因子和台站场地响应的基础上联合反演计算了瀑布沟库区67次构造地震和208次爆破地震的震源波谱参数,同时讨论了它们的时空特征。结果表明：瀑布沟库区Q值与频率的关系为Q（f）=47.1*f0.92;各台站的场地响应随频率变化不大,场地响应均在1附近。     

2006年温州珊溪水库地震序列特征

通过分析2006年2月温州珊溪水库地震序列的时空强分布特征,得到该序列具有①频度高、衰减慢、持续时间长;②震中分布集中且呈北西向展布;③震源浅;④各台站P波初动符号基本保持不变;⑤较大地震发生前,空间上出现空段,时间上表现为“增强—平静—发震”;⑥h值先变小后变大,b值缓慢变大等特点。结合地震应急时的预报实践,重点研究了地震趋势判断中比较有效的指标或参量,希望能为以后珊溪水库地震趋势的预报提供借鉴。     

吉木萨尔凹陷芦草沟组致密油储层微观孔喉结构研究?

通过微纳米 CT、FIB 双束扫描电镜等实验手段,对吉木萨尔凹陷二叠系芦草沟组致密油储层进行详细的探讨。研究发现,吉木萨尔凹陷二叠系芦草沟组储层为中孔-低渗、特低渗、低孔特低渗储层,孔隙以微纳米级为主,类型多样,主要有粒间孔（缝）、粒间溶孔、晶间孔、层间缝及微裂隙等。不同类型储集段,储层物性和孔隙结构差异较大：上甜点区砂屑云岩孔隙以粒间孔（缝）和溶孔为主,多为微米级;下甜点区灰质粉砂岩以粒间孔和晶间孔为主,孔隙多为纳米级,0.05～0.1μm;非甜点区的灰质炭质泥岩主要发育晶间孔、层间缝和微裂隙,裂隙宽约5～6μm。     

水库诱发地震中水库水体下方的地震波速比

以大桥水库MS4.6诱发地震和紫坪铺水库ML2.5诱发震群为例,研究了穿过水体下方的地震波的波速比在地震前后的变化.由彝海子台记录的穿过大桥水库水体下方的地震波所计算的波速比,在蓄水后4.6级主震前存在高值异常,反映库水对波速比有影响;由八角台记录的穿过紫坪铺水库水体下方的地震波所计算的波速比显示,在2006年8月28日后一时段库区东北部出现微小的波速比高值异常,结果于2006年10月至2007年2月在八角台附近的汶川水磨发生了2.5级水库诱发震群.因此认为,根据穿过水库水体下方的地震波射线计算的单台波速比,能够反映地震孕育过程中震源及周围地区介质特性的改变,可作为监测水库地震的一种手段.     

Estimation of Dry Fracture Weakness,Porosity, and Fluid Modulus Using Observable Seismic Reflection Data in a Gas-Bearing Reservoir

Fracture detection and fluid identification are important tasks for a fractured reservoir characterization. Our goal is to demonstrate a direct approach to utilize azimuthal seismic data to estimate fluid bulk modulus, porosity, and dry fracture weaknesses, which decreases the uncertainty of fluid identification. Combining Gassmann’s (Vier. der Natur. Gesellschaft Zürich 96:1–23, 1951) equations and linear-slip model, we first establish new simplified expressions of stiffness parameters for a gas-bearing saturated fractured rock with low porosity and small fracture density, and then we derive a novel PP-wave reflection coefficient in terms of dry background rock properties (P-wave and S-wave moduli, and density), fracture (dry fracture weaknesses), porosity, and fluid (fluid bulk modulus). A Bayesian Markov chain Monte Carlo nonlinear inversion method is proposed to estimate fluid bulk modulus, porosity, and fracture weaknesses directly from azimuthal seismic data. The inversion method yields reasonable estimates in the case of synthetic data containing a moderate noise and stable results on real data.     

渔洞水库地区地震活动性和构造应力场分析

统计了渔洞水库的水位变化规律,分析了水库蓄水前后库区及其附近地区的地震活动性和构造应力场特征。结果表明,水库蓄水前后研究区地震活动的图像、强度和频次都没有明显变化;水库蓄水和水位变化对研究区构造应力场没有明显的影响。     

考虑劣化屈服老化裂纹后混凝土水库堤坝排水边坡抗震性研究

针对在水库堤坝排水边坡混凝土裂纹的抗震性研究中,未考虑岩土体抗剪强度参数的劣化屈服效应以及混凝土裂纹的老化,存在抗震性判断结果准确率较差等问题,提出水库堤坝排水边坡混凝土考虑老化后产生裂纹的抗震性能研究方法。模拟强震下边坡混凝土的开裂破坏过程,根据D-P屈服准则,实现对闸墩混凝土材料的屈服判断。采用薄层整体单元模拟和分离式裂纹单元,实现混凝土裂纹的数值模拟,加载地震波后,获取混凝土裂纹的强震响应规律与破坏特征。实验结果可知,本文方法对坝体位移变化的研究精度高,得到的混凝土裂纹扩展范围更为准。运用本文方法对水库堤坝排水边坡混凝土的抗震性研究准确率以及可信度较高,说明本文方法具有一定的可取性。     

有效压力与饱和度变化的气藏多波时移地震AVO响应

天然气在开发过程中,储层有效压力和含气饱和度均会发生变化,研究有效压力和含气饱和度的变化对地震响应特征的影响,在基于时移地震的剩余气分布预测研究中具有重要意义。天然气和石油的声学性质有着明显的差异,油藏时移地震的研究成果不能直接应用于气藏,因此需要开展气藏的时移地震研究。利用Shapiro模型表征干岩石弹性模量随有效压力的变化,借助Batzle-Wang方程描述流体速度随压力的变化关系,联合Gassmann理论进行流体替代,表征饱和流体岩石速度随含气饱和度的变化,建立了饱和流体岩石速度随有效压力和饱和度变化的岩石物理模型。基于该模型,对不同含气饱和度和不同有效压力下的气藏储层模型进行了多波时移地震叠前振幅变化（AVO）模拟。结果表明多波时移地震AVO技术可以有效地区分有效压力变化和含气饱和度变化,为进一步开展气藏多波时移地震流体监测提供了理论参考依据。