Field survey of the East Java earthquake and tsunami of June 3, 1994

A field survey of the June 3, 1994 East Java earthquake tsunami was conducted within three weeks, and the distributions of the seismic intensities, tsunami heights, and human and house damages were surveyed. The seismic intensities on the south coasts of Java and Bali Islands were small for an earthquake with magnitudeM 7.6. The earthquake caused no land damage. About 40 minutes after the main shock, a huge tsunami attacked the coasts, several villages in East Java Province were damaged severely, and 223 persons perished. At Pancer Village about 70 percent of the houses were swept away and 121 persons were killed by the tsunami. The relationship between tsunami heights and distances from the source shows that the Hatori's tsunami magnitude wasm=3, which seems to be larger for the earthquake magnitude. But we should not consider this an extraordinary event because it was pointed out byHatori (1994) that the magnitudes of tsunamis in the Indonesia-Philippine region generally exceed 1–2 grade larger than those of other regions.     

金沙江地震带强震动及其与现今弱震活动关系

包括川滇菱块及马边－大关，宣威－弥勒地区在内的金沙江地震带记载（录）了川滇两省发生的绝大部分中、强以上地震，为我国西南一主要地震区。本文重点研究了该范围内强震的重复性及现今弱震密集区的强震危险性问题。金沙江地震带强震具有很高的原地重复性，７级以上强震原地重复率达６５．４％，平均复发时间１５７年；６级地震原地重复率达４１．８％，平均复发时间为２７．２年。川滇地区现今弱震活动密集区在活动期内本身发生６级以上强震的可能性很小。四川地区大多数情况下强震发生在距密集区４０－５０千米处，云南情况较复杂。但在作今后较长时间危险性分析预测时，现今弱震密集区本身仍有发生６级地震的危险，虽然发生７级以上地震可能性不大。     

软弱结构面水流冲刷形成集中渗漏通道机制研究

软弱结构面塑性程度高、强度低,在地下水长期作用下,很易导致岩体产生变形、形成集中渗漏通道及渗透破坏。软弱结构面的渗透稳定性,一直是水利水电工程的重要工程地质及水文地质问题之一,目前对其渗透破坏机理的认识还存在不少尚未解决的问题。针对已有对基岩软弱结构形成集中渗漏通道研究的不足,本文在软弱结构面内讨论渗透变形问题,主要探讨了软弱结构面受水流冲刷发展的机制,以及土粒起动处于不同位置时的临界流速及相应隙宽。最后介绍了在适当地质等条件下,基岩软弱结构面可形成集中渗漏通道的实例。     

Analysis of seismic dynamical systems

A procedure is presented for the analysis of complex stationary time series for which the Fourier power spectra reveals broadband noise or broadened pulses. We first determine the Hurst exponent from which we may know whether the time series under study is mainly random or if the data points present correlations. If the data are correlated, a chaotic analysis will reveal whether they may be interpreted as a low dimensional nonlinear system (defined by a low correlation dimension and a finite and positive Kolmogorov entropy and largest positive Lyapunov exponent) or as a stochastic process. We have studied three kind of temporal series: inter-event time series of infrasonic pulses recorded at Stromboli volcano, and, S-coda waves and microseisms, that have been recorded at the eastern Pyrenees. Results show that microseisms and Coda waves can be modeled as a low dimensional deterministic system, Correlation dimensions 2.3, 3.2, respectively. At the contrary infrasonic has resulted stochastic. This chaotic character can be attributed to the medium properties. Coda waves with scattering through a fractal distribution of scatters or to multiple reflection inside resonators (for example sedimentary basins) and microseisms as a propagation of wave guide of variable cross section which have the same temporal characteristics as a nonlinear forced oscillator.     

Generalisation of a Nonlinear Dynamo Model

In order to gain a better understanding of the physical processes underlying fast dynamo action it is instructive to investigate the structure of both the magnetic field and the velocity field after the dynamo saturates. Previously, computational results have been presented (Cattaneo, Hughes and Kim, 1996) that indicate, in particular, that Lagrangian chaos is suppressed in the dynamical regime of the dynamo. Here we extend their model by removing the assumption of neglecting the inertial term. This allows for an investigation into the effect of this term on the evolution of the dynamo via a comparison of the two models. Our results indicate that this term plays a crucial role in the physics of the dynamo.     

河流相储层特征及识别:一个老河口油田的实例分析(英文)

河流相储层是一种重要的储层类型,寻找河道砂体是油气勘探的一项重要工作。但是河道变迁比较频繁,叠置比较严重,加之地震资料本身信噪比和分辨率的限制,河流相储层的精细描述至今仍存在一定的困难。本文以胜利油田老河口三维工区为例,首先研究了本区河流相储层的基本特征,发现该类储层剖面上呈强相位、切片上连续性好和频谱上呈低频特征;通过颜色处理和地震精细解释,发现本区河流相储层存在类串珠状特征,为了验证这一观测结果,我们用正演模拟分析了其形成机理,为在类似工区识别此类古河道找到了新的途径;应用多属性融合和RGB显示技术,河道下切特征更加明显,很好地彰显了河道结构特征,提高了河道识别能力;最后,我们研究并开发了多子波检测技术,检测出更多河流相弱反射信息。     

Study of site effects in the area of Nocera Umbra (Central Italy) during the 1997 Umbria-Marche seismic sequence

During the M_L = 5.6 and 5.8 earthquakes occurredin central Italy on 26 September 1997 the historiccentre of Nocera Umbra, lying on top of a 120 m highhill, was diffusely damaged (VII-VIII degrees of MCSintensity). Some recently built houses in the modernpart of the town suffered an even higher level ofdamage. A temporary seismic array was deployed toinvestigate a possible correlation between localamplifications of ground motion in this area and theobserved pattern of damage. After a geologic andmacroseismic survey, eight sites were selected asrepresentative of different local conditions, such astopographic irregularities, sharp hard-to-softlithology transitions, alluvium-filled valleys, andboth undisturbed and deformed rocks.Horizontal-to-vertical spectral ratios for bothmicrotremor and earthquake recordings, as well asspectral ratios referred to undisturbed rock sites,were used to quantify local variations of groundmotion. In spite of the diffuse damage in the historiccentre of Nocera Umbra, a small amplification isobserved at the stations on the hill's top. Thissuggests that the higher vulnerability of the ancientbuildings mainly accounts for the diffuse damage inthat part of the town. In the frequency band ofengineering interest (1 to 10 Hz) the largestamplifications of ground motion are found at softsites: in the Topino river valley, where many episodesof severe structural damage occurred, spectralamplification is significant over a broad frequencyband ranging from 2 Hz to more than 20 Hz. Inparticular, in the central part of the valley highamplification (> 4) is found from 3 to 10 Hz,reaching a maximum of 20 around 4 Hz. At the edge ofthe valley, close to the soil-to-rock transition,amplification is as large as 10 in a frequency bandranging from 4 to more than 20 Hz. A significantamplification (by a factor of 10 around 10 Hz) isobserved also at one of the rock sites, possibly dueto the presence of a cataclastic zone related to theactivity of a regional fault that altered themechanical properties of the rock.     

Chaotic seismic faulting with a mass-spring model and velocity-weakening friction

We present a systematic analysis of the dynamical behavior introduced by fault zone heterogeneities, using a simple mass-spring model with velocity-weakening friction. The model consists of two sliding blocks coupled to each other and to a constant velocity driver by clastic springs. The state of this system can be characterized by the positions of the two blocks relative to the driver. Symmetry stabilizes the system and generates only cyclic behavior. For an asymmetric system where the frictional forces for the two blocks are not equal, the solutions exhibit chaotic behavior. The transition from stable cyclic behavior to chaos is characterized by the period-doubling route to chaos. Lyapunov exponents are computed to quantify the deterministic chaos and to locate the onset of the chaotic evolution in parameter space. In many examples of deterministic chaos, chaotic behavior of a low-order system implies chaos in similar higher order systems. Thus, our results provide substantial evidence that crustal deformation is an example of deterministic chaos.     

用1：5万磁异常特征圈定贵州水城-艾家坪地区成矿靶区

对1：5万高精度磁异常原始资料数据处理,进行化极、延拓计算7个不同上延高度异常,分析对比所有资料,结合地物化资料,对磁异常平面进行特征分区。又根据已知的白马洞（区内）-杉树林（区外）铅锌矿床成矿带及区内异处的铅锌、铜、锰等矿床（点）的成矿规律和分布特点,圈定了8个异常成矿靶区,19个大型的浅层局部负磁异常,均为有一定找矿意义的磁异常,并推测它们可能为岩体与矿致磁异常（铅锌、铜、锰、铁）等综合引起,在岩体（浅表隐伏的花岗岩珠或岩枝）与围岩接触带、层间破碎带上,应是赋矿的有利部位。     

不良地质段双洞交叉开挖三维有限元分析

积石峡水电站泄洪洞与导流洞交叉段形成了跨度为28 m,高度为22 m类似城门洞形的大断面洞室,该洞段围岩呈层状分布,且有一软弱夹层穿过拱顶,对洞室稳定极为不利。针对这一实际工程问题,确定了开挖方案和支护措施,采用三维非线性有限元分析了该处的围岩应力和变形随开挖进行的变化和围岩的稳定性,并考虑了位于拱顶的软弱夹层对交叉段洞室开挖围岩稳定的影响,对于其他类似工程,其结果具有良好的参考价值。