Results of deep reflection seismic profiling in the Oberpfalz (Bavaria)

Summary. In order to investigate the target area of the Continental Deep Drilling (KTB) in the Oberpfalz a network of six seismic reflection lines was acquired in 1985 using the Vibroseis technique. The average length of these lines was 50 km. In addition, the 185 km long NW/SE striking line DEKORP 4 with its short appendix line 4-Q of 40 km length was acquired with the same technique. The results reveal a strongly structured upper crust. This is in contrast with previous surveys in the German Variscides which show a poorly reflective upper crust and a strongly reflective lower crust. Except for the S part of DEKORP 4 in the Oberpfalz area the Mono is only weakly reflective. In addition to the Vibroseis survey 96 shots along line DEKORP 4 were recorded by conventional reflection techniques and by portable reflection and refraction stations from university institutes and geological surveys in order to obtain wide-angle reflection and expanding spread data.     

Crustal structure at the easternmost termination of the Variscan belt based on CELEBRATION 2000 and ALP 2002 data

The eastern margin of the Variscan belt in Europe comprises plate boundaries between continental blocks and terranes formed during different tectonic events. The crustal structure of that complicated area was studied using the data of the international refraction experiments CELEBRATION 2000 and ALP 2002. The seismic data were acquired along SW–NE oriented refraction and wide-angle reflection profiles CEL10 and ALP04 starting in the Eastern Alps, passing through the Moravo-Silesian zone of the Bohemian Massif and the Fore-Sudetic Monocline, and terminating in the TESZ in Poland. The data were interpreted by seismic tomographic inversion and by 2-D trial-and-error forward modelling of the P waves. Velocity models determine different types of the crust–mantle transition, reflecting variable crustal thickness and delimiting contacts of tectonic units in depth. In the Alpine area, few km thick LVZ with the Vp of 5.1 km s^− 1 dipping to the SW and outcropping at the surface represents the Molasse and Helvetic Flysch sediments overthrust by the Northern Calcareous Alps with higher velocities. In the Bohemian Massif, lower velocities in the range of 5.0–5.6 km s^− 1 down to a depth of 5 km might represent the SE termination of the Elbe Fault Zone. The Fore-Sudetic Monocline and the TESZ are covered by sediments with the velocities in the range of 3.6–5.5 km s^− 1 to the maximum depth of 15 km beneath the Mid-Polish Trough. The Moho in the Eastern Alps is dipping to the SW reaching the depth of 43–45 km. The lower crust at the eastern margin of the Bohemian Massif is characterized by elevated velocities and high Vp gradient, which seems to be a characteristic feature of the Moravo-Silesian. Slightly different properties in the Moravian and Silesian units might be attributed to varying distances of the profile from the Moldanubian Thrust front as well as a different type of contact of the Brunia with the Moldanubian and its northern root sector. The Moho beneath the Fore-Sudetic Monocline is the most pronounced and is interpreted as the first-order discontinuity at a depth of 30 km.     

The Tornquist Zone, a north east inclining lithospheric transition at the south western margin of the Baltic Shield: Revealed through a nonlinear teleseismic tomographic inversion

From July 1996 to August 1997 the TOR project operated 130 seismographs in North Germany, Denmark and South Sweden, with the aim of collecting signals from local, regional and teleseismic earthquakes. This data set is particularly interesting since the seismic antenna crosses the most significant geological boundary in Europe, the Tornquist Zone, which in the northern part is the border between the Baltic Shield and the younger European lithosphere. Previous studies have shown significant physical changes in the crust and upper mantle across this transition zone, including two independent teleseismic tomographic studies of the TOR data set. But these two studies disagree on the orientation of the slope of the transition. Both studies used an iterative linearized inversion method. We will in this work Preprint submitted to Elsevier Science 27 July 2005 present an inversion based on Bayesian statistics, where the solution space is examined in order to study a very large number of tomographic solutions and to examine the solution uniqueness and uncertainty. The method is applied to measurements of 3345 relative teleseismic P-phase travel times from 48 teleseismic earthquakes with good azimuthal coverage with respect to the great circle arc of the TOR array. We find the lithospheric transition to be a north east inclination of around 30° to 45° off vertical.     

深层地震勘探激发井深探讨

深层地震勘探野外资料采集的关键是在保证原始资料一定信噪比的基础上,同时兼顾分辨率,激发井深是决定资料品质的重要因素之一。通过对虚反射滤波作用分析,提出了充分利用虚反射能量设计最佳激发井深,增强下传地震波能量的采集方法。理论分析和试验资料表明,在高速层下4～7m的最佳激发岩性深度是深层勘探的理想井深。     

吸水剖面综合解释方法及应用

吉林油田同位素吸水剖面测井采用~(113)In同位素追踪技术,根据同位素追踪过程解释基本可以判断配水层段吸水情况。但是在注水井存在沾污、大孔道以及串槽等影响时,吸水面积确定比较困难。在同位素测井中增加井温、流量参数,通过多参数综合解释,不仅可以对沾污影响进行合理校正,确定准确的小层吸水量,而且能够正确判断各级封隔器、配水器的工作情况,在地层存在大孔道的情况下,确定地层的吸水面积。吸水剖面综合解释方法在吉林油田已普遍应用,见到明显的效果。     

亚洲地震委员会(ASC)第七次学术大会暨日本地震学会(SSJ)秋季会议在日本筑波召开

由亚洲地震委员会和日本地震学会联合主办,日本多个学术机构参与协办的第七届亚洲地震委员会学术大会暨日本地震学会秋季会议于2008年11月24--28日在日本筑波(Tsukuba)举行.     

几个天然镁铝榴石的穆斯堡尔效应的研究

穆斯堡尔效应是一种无反冲的核γ射线的共振吸收现象,它是1958年由穆斯堡尔(R.L.M(?)ssbauer)发现的。由于穆斯堡尔效应产生的γ射线共振吸收谱线的能量宽度接近原子核能级的自然线宽,以及无反冲γ射线共振吸收(或散射)对γ射线能量变化十分灵敏,因此,可以把共振吸收的原子核当做灵敏的探针,测量固体中有关的原子核与核所在位置上固体的化学环境间的超精细相互作用。近些年来,穆斯堡尔效应已广泛应用于物理学、化学、生物学及矿物学的研究中来,穆斯堡尔谱仪已成为这些学科的重要研究工具之一。     

A Nonlinear Model of Surf Beat

A nonlinear short-wave-averaged (surf beat) model is presented. The model is based on that of Roelvink (1993), but the numerical techniques used in the solution are based on the so-called weighted-averaged flux (WAF) method (eg Watson et al., 1992), with time-operator splitting used for the treatment of some of the source terms. This method allows a small number of computational points to be used, and is particularly efficient in modelling breaking long waves. The short-wave (or primary-wave) energy equation is solved using a more traditional Lax-Wendroff technique. Results of validation indicate that the model performs satisfactorily in most respects.