An investigation of seismicity for western Anatolia

In order to investigate the seismicity of western Anatolia limited with the coordinates of 36°–40° N, 26°–32° E, Gutenberg–Richter magnitude–frequency relation, seismic risk and recurrence period have been computed. The data belonging to both the historical period before 1900 (I₀ ≥ 5.0 corresponding to M_S ≥ 4.4) and the instrumental period until the end of 2006 (M_S ≥ 4.0) has been used in the analysis. The study area has been divided into 13 sub-regions due to certain seismotectonic characteristics, plate tectonic models and geology of the region. All the computations have been performed for these sub-regions, separately. According to the results, a and b values in the computed magnitude–frequency relations are in the intervals 3.19±0.17 – 5.15±0.52 and 0.42±0.05 – 0.66±0.07, respectively. The highest b values have been determined for sub-regions 3 and 12 (Demirci-Gediz and Gökova Gulf-Mu?la-Gölhisar). The lowest b values have also been determined for sub-regions 1 and 9 (Bal?kesir and Bodrum-?stanköy). Finally, seismic risk and recurrence period computations from a and b values have shown as expected that sub-regions 1 and 9 which have the lowest b values and the highest risks and the shortest-recurrence periods.     

Statistical aspects of Parkfield earthquake sequence and Parkfield prediction experiment

This note discusses three interconnected statistical problems concerning the Parkfield sequence of moderate earthquakes and the Parkfield prediction experiment: (a) Is it possible that the quasi-periodic Parkfield sequence of characteristic earthquakes is no uncommon, specific phenomenon (the research hypothesis), but can be explained by a preferential selection from available earthquake catalogs? To this end we formulate the null hypothesis (earthquakes occur according to the Poisson process in time and their size follows the Gutenberg-Richter relation). We test whether the null hypothesis can be rejected as an explanation for the Parkfield sequence. (b) If the null hypothesis cannot be refuted, what is the probability of magnitude m ≥ 6 earthquake occurrence in the Parkfield region? (c) The direct goal of the Parkfield experiment is the registration of precursory phenomena prior to a m6 earthquake. However, in the absence of the characteristic earthquake, can the experiment resolve which of the two competing hypotheses is true in a reasonable time? Statistical analysis is hindered by an insufficiently rigorous definition of the research model and inadequate or ambiguous data. However, we show that the null hypothesis cannot be decisively rejected. The quasi-periodic pattern of intermediate size earthquakes in the Parkfield area is a statistical event likely to occur by chance if it has been preferentially selected from available earthquake catalogs. The observed magnitude-frequency curves for small and intermediate earthquakes in the Parkfield area agree with the theoretical distribution computed on the basis of a modified Gutenberg-Richter law (gamma distribution), using deformation rates for the San Andreas fault. We show that the size distribution of the Parkfield characteristic earthquakes can also be attributed to selection bias. According to the null hypothesis, the yearly probability of a m ≥ 6 earthquake originating in the Parkfield area is less than 1%, signifying that several more decades of observation may be needed before the expected event occurs. By its design, the Parkfield experiment cannot be expected to yield statistically significant conclusions on the validity of the research hypothesis for many decades.     

The Bajool earthquake sequence of 1991, and implications for the seismicity of central Queensland

The township of Bajool, situated 30 km south of Rockhampton, Queensland, experienced two minor earthquakes, each of Richter magnitude 2.9 on 10 June 1991. The foci were located 7 km north of Bajool, at a depth of less than 10 km. The felt intensity in Bajool was generally IV‐V, with minor damage occurring to several houses. There were several foreshocks and four aftershocks. The events may represent reactivation of a thrust fault, close to its junction with an inferred transform fault, the Fitzroy River Fault. These events demonstrate that the quiescence of central Queensland is apparent only, and that the recently installed University of Central Queensland Regional Network will provide a useful contribution to the understanding of earthquakes occurring along a passive continental margin.     

矿井小断层延伸长度的多元线性回归预测模型

矿井小断层普遍存在且错综复杂,对煤层开采影响很大。根据黄河北煤田赵官井田7号煤层小断层资料,选取断层走向延展长度、断层落差和断层倾角3个因素,运用多元回归分析方法,建立了7号煤层NE、NEE和NW向小断层延伸长度的预测模型。实际应用表明,该模型的预测精度较高,比较符合实际情况。     

Correlation between tides and seismicity in Northwestern South America: The case of Colombia

We present the first systematic exploration of earth tides-seismicity correlation in northwestern South America, with a special emphasis in Colombia. For this purpose, we use a dataset of ∼167,000 earthquakes, gathered by the Colombian Seismological Network between 1993 and 2017. Most of the events are intermediate-depth earthquakes from the Bucaramanga seismic nest and the Cauca seismic cluster. For this purpose, we implemented a novel approach for the calculation of tidal phases that considers the relative positions of the Earth-Moon-Sun system at the time of the events. After applying the standard Schuster test to the whole dataset and to several earthquake samples (classified by time, location, magnitude and depth), we found strong correlation anomalies with the diurnal and monthly components of the tide (global log(p) values around −7.0 for the diurnal constituent and −12.1 for the monthly constituent), especially for the intermediate depth events. These anomalies suggest that around 16% of the deep earthquakes in Colombia may be triggered by tides, especially when the monthly phase is between 350°-10°. We attribute our positive results, which favor the tidal-triggering hypothesis, in contrast to previous negative ones to: 1) the size of our dataset, and 2) the method we used to calculate tidal phases. Anyone willing to reproduce our results or to apply our methodology to custom datasets can use the public information system tQuakes that we developed for this work.     

The devastating Muzaffarabad earthquake of 8 October 2005: New insights into Himalayan seismicity and tectonics

The recent earthquake of 8 October 2005 in the Muzaffarabad region in western Himalaya destroyed several parts of Pakistan and the north Indian state of Jammu and Kashmir. The earthquake of magnitude 7.6 claimed more than 80,000 lives, clearly exposing the poor standards of building construction — a major challenge facing the highly populated, earthquake prone, third world nations today. In this paper, we examine variations in the stress field, seismicity patterns, seismic source character, tectonic setting, plate motion velocities, GPS results, and the geodynamic factors relating to the geometry of the underlying subsurface structure and its role in generation of very large earthquakes. Focal mechanism solutions of the Muzaffarabad earthquake and its aftershocks are found to have steep dip angles comparable to the Indian intra-plate shield earthquakes rather than the typical Himalayan earthquakes that are characterized by shallow angle northward dips. A low p-value of 0.9 is obtained for this earthquake from the decay pattern of 110 aftershocks, which is comparable to that of the 1993 Latur earthquake in the Indian shield — the deadliest Stable Continental Region (SCR) earthquake till date. Inversion of focal mechanisms of the Harvard CMT catalogue indicates distinct stress patterns in the Muzaffarabad region, seemingly governed by an overturned Himalayan thrust belt configuration that envelops this region, adjoined by the Pamir and Hindukush regions. Recent developments in application of seismological tools like the receiver function technique have enabled accurate mapping of the dipping trends of the Moho and Lithosphere–Asthenosphere Boundary (LAB) of Indian lithosphere beneath southern Tibet. These have significantly improved our understanding of the collision process, the mechanism of Himalayan orogeny and uplift of the Tibetan plateau, besides providing vital constraints on the seismic hazard threat posed by the Himalaya. New ideas have also emerged through GPS, macroseismic investigations, paleoseismology and numerical modeling approaches. While many researchers suggest that the Himalayan front is already overdue for several 8.0 magnitude earthquakes, some opine that most of the front may not really be capable of sustaining the stress accumulation required for generation of great earthquakes. We propose that the occurrence of great earthquakes like those of 1897 in Shillong and 1950 in Assam have a strong correlation with their proximity to multiple plate junctions conducive for enormous stress build up, like the eastern Himalayan syntaxis comprising the junction of the India, Eurasia plates, and the Burma, Sunda micro-plates.     

中国不同类型盆地油气资源丰度统计特征及预测模型

油气资源丰度是油气资源评价的一项关键参数,取准资源丰度对于客观评价资源潜力十分重要。本文立足于类比刻度区进行统计分析,探索建立资源丰度预测模型的思路并开展研究;统计表明我国主要含油气盆地的常规油气资源普遍为中低丰度,并以特低丰度和低丰度资源为主,仅局部优越区块为高丰度。据此筛选刻度区数据,并按照裂谷、克拉通、前陆3种基本盆地类型分析常规油气资源丰度与相关地质参数的关系。不同类型盆地的油气资源丰度均与烃源岩生烃强度、圈闭面积系数、区域不整合次数3项主控地质参数具有显著的相关性,但不同类型盆地油气资源丰度与3项主控地质参数之间关系的变化趋势存在差异,拟合的单参数地质模型能够较好描述3项主控地质参数单独与不同类型盆地油气资源丰度的定量关系。由此建立了基于烃源岩生烃强度、圈闭面积系数、区域不整合次数3项主控地质参数的油气资源丰度预测模型,能够快速、准确求取不同类型盆地的常规油气资源丰度。预测模型在实际应用中效果较为理想,具有易操作、易推广的优点,实用价值较高。     

考虑应力应变时间效应的桩基长期沉降计算方法

土体的应力应变时间效应对桩基长期沉降有重要影响。在长期荷载作用下桩基的沉降主要包括两个部分：桩尖刺入量和桩底土体的蠕变压缩沉降。采用Mesri蠕变模型描述土体的蠕变行为，用桩的Mindlin应力公式计算桩端和桩侧荷载在桩端平面以下产生的附加应力，用Boussinesq应力公式计算承台分担荷载产生的应力。分别给出了桩尖刺入量和桩底土体蠕变压缩量的计算方法，从而提出了一种考虑土体蠕变效应的桩基长期沉降计算方法。计算结果与桩基长期监测结果较为吻合，表明在获得可靠的计算参数后可用提出的方法估算桩基长期沉降。     

A statistical comparison of various source formulations for explosions and earthquakes

Stochastic models are derived for two source formulations for explosions. Using this kind of model, a comparison is made between source time functions due to Blake, Haskell, Mueller and Murphy, and Von Seggern and Blandford, for explosions, and between -square (Aki, Brune)and -cube (Aki, Haskell)models for earthquakes. When seeking a stochastic model for records of Rayleigh waves from atmospheric explosions, the k-model corresponding to Haskell's time function was found to be an appropriate choice.     

Statistical analysis of the effective stress method and modifications for prediction of ultimate bond strength of soil nails

Uncertainty in the predicted ultimate pullout strength of soil nails can be significant due to the complexity of nail–soil interactions, inherent variability in soil properties and the effects of nail installation. The paper first presents a statistical evaluation of the accuracy of ultimate bond strength of soil nails using the effective stress method (ESM) equation that has been adopted in Hong Kong. A total of 113 ultimate nail capacity data points from field pullout tests were collected from the literature and used to estimate the accuracy of the current ESM. Based on the available data, the current ESM default pullout model is found to be excessively conservative (on average) by at least a factor of three. The spread in prediction accuracy measured by the coefficient of variation (COV) of bias is in the range of 36–43 % after removing anomalous test data. Here, bias is the ratio of measured to predicted pullout load capacity. In addition, the accuracy of the current ESM equation for prediction of nail bond strength is shown to be dependent on the magnitude of predicted ultimate bond strength and magnitude of nominal vertical effective stress which is undesirable. The paper examines four candidate-modified bond strength equations with empirical coefficients that have been back-fitted to measured bond strengths to improve the overall accuracy of the equation and to reduce or remove the undesirable dependencies noted above. One equation with an empirically corrected stress-dependent term is judged to be the best candidate model based on the mean of bias values, spread (COV) of bias values, lack of dependencies and simplicity. Finally, the relative contributions of random variability in soil shear strength to measurement bias in bond strength (prediction accuracy) for each soil type are computed for the best bond strength model. Analysis of the contribution of soil shear strength to prediction accuracy showed that the combination of variability due to factors other than soil shear strength was greater than the variability in soil shear strength alone, where the latter is defined by the soil secant friction coefficient.     

泥岩巷道围岩弹塑性参数反演分析与长期稳定性预测

以实测的围岩蠕变变形资料为基础,基于现场监测所获得的蠕变本构模型,对某一矿区泥岩体的力学参数进行了弹塑性反演分析,得到的巷道围岩体基本力学参数分别为弹性模量E=2.0 GPa,凝聚力c=1.31 MPa,内摩擦角? =24º。待反演参数水平均值的极差结果显示,通过极差的大小可以判断岩土力学参数的敏感性,对蠕变的影响而言,凝聚力最敏感,其次是内摩擦角,弹性模量再次之。在此基础上,利用反演所得的围岩基本力学参数进行了正演,计算得到了各测点处对应的蠕变位移增量,与实测值相比吻合较好,表明反分析所获得的岩体材料参数综合反映了巷道围岩的力学特性。最后,对巷道围岩变形大小及塑性区范围进行了预测。     

基于因子分析方法解析降雨分量的渗流统计模型及应用

基于原型监测资料的渗流统计模型可用于分析枢纽区的渗流动态,而其中因子的选择影响模型的有效性。针对抽水蓄能电站环境变量监测频率的不一致性,对输水系统所在山体的地下水水位进行因子分析并对提取出的公共因子进行识别,而后将其中的降雨因子应用于基于滞后效应的渗流统计模型中。计算结果表明,与不考虑降雨因子相比较,所建模型可以有效地提高模型精度。因而,该模型适用于环境变量监测频率不一致或缺少相关资料的情形。     

Integrated Interpretation of Interwell Connectivity Using Injection and Production Fluctuations

A method to characterize reservoirs, based on matching temporal fluctuations in injection and production rates, has recently been developed. The method produces two coefficients for each injector–producer pair; one parameter, λ, quantifies the connectivity and the other, τ, quantifies the fluid storage in the vicinity of the pair. Previous analyses used λ and τ separately to infer the presence of transmissibility barriers and conduits in the reservoir, but several common conditions could not be easily distinguished. This paper describes how λ and τ can be jointly interpreted to enhance inference about preferential transmissibility trends and barriers. Two different combinations are useful: one is a plot of log (λ) versus log (τ) for a producer and nearby injectors, and the second is a Lorenz-style flow capacity (F) versus storativity (C) plot. These techniques were tested against the results of a numerical simulator and applied to data from the North Buck Draw field. Using the simulated data, we find that the F–C plots and the λ–τ plots are capable of identifying whether the connectivity of an injector–producer well pair is through fractures, a high-permeability layer, multiple-layers or through partially completed wells. Analysis of data from the North Buck Draw field shows a reasonable correspondence between τ and the tracer breakthrough times. Of two possible geological models for Buck Draw, the F–C and λ–τ plots support the model that has less connectivity in the field. The wells in fluvial deposits show better communication than those wells in more estuarine-dominated regions.     

地面沉降泊松旋回预测方法：以上海地面沉降长期预测为例

在上海地面沉降长期预测研究的实际经验基础上,对泊松旋回模型进行了一些改进,建立了地面沉降泊松旋回预测的数学模型,提出了应用于预测时的技术处理方法。对预测的上海部分标点1995—2050年地面沉降量10～37cm进行了一定评估,认为在现有研究水平上是可信的。引入衰减系数于泊松旋回模型之中是本方法的特色之一。     

Pairing geotechnics and fluvial hydraulics for the prediction of the hazard zones of an exceptional flooding

The direct consequences of exceptional floods are usually considered to be limited to the maximum flooding zone created downstream. However, considering the magnitude of the flows, the morphology of the flooded zone could undergo deep changes. To predict the hazard zone on a river undergoing exceptional flooding, numerical simulations are widely used. In this article, the simulation of the evolution of river reaches resulting from such catastrophic events is performed by coupling the hydraulic and sediment transport numerical model GSTARS with a developed slope stability model based on the Bishop’s simplified method. This is a novel methodology for the delimitation of hazard zones along riverbanks by taking into consideration not only the flood risks but also the possible induced landslides. Indeed, each section of the river reach is subject to changes caused by the river hydraulics and the associated erosion or sediment deposition and also undergoes profile changes caused by possible landslides. The initial hydraulic and geotechnical characteristics are first defined and then used to test the stability of several slopes of representative sections of the river reaches before the dam break. Validation tests are performed on specific reaches of the Outaouais River (Quebec) undergoing a dam break flood.     

ARIMA模型在新疆喀什地区中长期降水量预测中的应用研究

为研究新疆喀什地区降水量中长期预测问题,结合ARIMA模型对新疆喀什地区的降水量进行预测,利用喀什地区两个子流域1950-2015年实测年降水数据分析其模型的适用性和预测精度。结果表明:ARIMA模型可较好的模拟喀什地区的年降水量,具有较好的预测精度,模拟降水量和实测降水量之间的误差相对值低于20%,绝对误差也可控制在15 mm以内;从空间角度分析,降水总体分布从东向西逐步递减,预测结果和实际降水空间分布状况较为吻合,可达到乙级精度标准。研究成果对于喀什地区中降水量长期预测具有较好的参考价值。     

Seismic Risk Assessment for the Territory of Armenia and Strategy of its Mitigation

The original methods of seismic risk assessment based on the main factors, defining the high level of seismic risk in Armenia, are used in this paper. Based on the analysis carried out, an assessment is made about the fact, that the capital of Armenia, Yerevan, is the most risk exposed area. A strategy for seismic risk reduction, derived from local peculiarities and the level of seismic risk, is presented. Improving the resisting of existing buildings and constructions to seismic damage, based on the grounds of new technologies elaborated by NSSP RA, is emphasised in this strategy.     

考虑蠕变性状的港区软土地基参数反演和长期沉降预测

结合上海某集装箱码头建设项目,针对本工程深厚淤泥质黏土的场地条件,引入Mesri蠕变模型考虑堆场地基的长期蠕变变形。利用施工期和工后短期实测分层沉降资料,由最小二乘法建立目标函数,运用分层迭代反演方法反演得到各软土层的黏弹性参数;将反演得到的土层参数代入自行编制的沉降计算软件,计算得到地基沉降量,并将计算值与实测值进行对比,对比结果证明了参数反演的可靠性;利用反演得到的土层参数对工后的长期沉降进行了预测,为本工程的安全运营提供了指导。     

Statistical methods for analysis and mapping of flysch-type sediments

To present a model for flysch deposition involves the simultaneous representation of many parameters. The most significant of these are arenite-lutite bed thickness ratio, mean and variance of arenite-bed thickness, mean palaeocurrent direction and the primary directional structures yielding them. Field and flume data suggest that arenite-bed thickness decreases exponentially away from source, with a complementary increase in siltstone bed thickness in a turbidite fan. If H_A, H_L. are arenite and lutite bed thicknesses in a couplet (the unit of bedding at a flysch outcrop), then where m and R are constants of the outcrop in the turbidite wedge. Field evidence suggests m= 1, so that R-values allow for a classification of couplets at an outcrop or within a zone. Maximum H_A, H_L. values are indicative of proximal deposition from turbidites, and usually provide transverse directional structures, as does (H_A) max. Arenite bed thickness can be considered as thick beds or thin beds according to whether they exceed a chosen thickness, say t cm. If 15 cm be chosen, the percentage thick arenite-bed thickness H_A1 and thin arenite bed thickness percentage, H_A2 can be represented with H_L. (siltstone bed thickness percentage) over twenty-five couplets, as one point on a triangular diagram. The mean palaeocurrent direction Nφ° E is represented as an arrow through the point, a colour (point or arrow) being used to distinguish the directional structure (flute, ripple, groove, foreset, etc.) producing it. Flysch examples from Ordovician, Silurian and Devonian in Central Victoria are thus interpreted in terms of proximal and distal emplacement. In cases where bedding detail is clear, A + B, C and D + E divisions substitute for H_A1H_A2 and H_L. respectively, for a unit of 1 m thickness of outcrop on the triangular diagram. If thick arenite bed thickness percentage be plotted against total arenite bed thickness percentage, the linear plot of points for outcrop samples results on log-log paper. Limiting lines of the form log H_A1= m log H_A+ log C (m, C constants) demarcate the field. Parallel and equally spaced lines with values C₁, C₂, C₃,…C_n subdivide this into sub-fields. If the determinations for H_A1 in any one sub-field be plotted on a locality map considering only MAXIMUM H_A1 values, and the H_A1H values conveniently contoured, trends emerge which closely agree with the modal palaeocurrent directions in the case of the Llandovery Deep Creek Flysch 25 km NNW of Melbourne, Australia.     

金华市某岩质滑坡成因机制分析及发展趋势预测

为探究金华市某岩质滑坡成因机制,多方面分析表明该滑坡是在固有内部因素条件下由地下水活动诱发产生的。为评价滑坡发展趋势,解决陈旧信息和波动性数据造成的传统灰色GM(1,1)模型预测精度较低的问题,提出一种利用动态新陈代谢和马尔科夫模型对原始灰色GM(1,1)模型改进的方法。通过新陈代谢理论来实现数据的动态更新,使得灰色GM(1,1)动态模型的预测值更加接近最新的变化趋势。利用马尔科夫模型对得到的灰色动态新陈代谢GM(1,1)模型预测值进行修正,提高了模型的预测精度。预测结果表明,灰色-马尔科夫动态新陈代谢GM(1,1)模型在滑坡形变预测中的预测平均相对误差相比于传统的灰色GM(1,1)模型降低了70%。对于波动性较大的滑坡监测数据,灰色-马尔科夫动态新陈代谢GM(1,1)模型预测精度远优于传统灰色GM(1,1)模型,具有实际的参考价值。金华市某岩质滑坡监测数据和预测结果研究表明,该滑坡发展趋势不稳定,需采取适当的防治措施。