On estimating the earthquake-induced changes in hydrogeological properties of the Choshuishi Alluvial Fan, Taiwan

The hydrological response of the Choshuishi alluvial fan to the 1999 Chi-Chi earthquake shows that the earthquake did impact the aquifer. The possible earthquake-induced changes in hydrogeological properties were investigated in this study. First, contour maps of the hydrologic anomaly, seismic factors, and vertical ground-surface displacement were compared qualitatively. Bulls eye patterns were found on the contour maps of hydraulic conductivity, coseismic groundwater-level change and vertical ground-surface displacement but did not occur with other seismic factors. The more permeable zones of the aquifer were found to coincide with the locations of greater vertical ground-surface displacement and coseismic groundwater-level change in the 1999 Chi-Chi earthquake. This indicates that the change of the hydrogeologic properties of Choshuishi alluvial fan due to the 1999 Chi-Chi earthquake may have mainly occurred in the highly permeable zones. Fractal, cross semivariogram and cross correlogram analyses were performed to quantitatively measure the persistency, variability and similarity, respectively, of spatial hydrologic response, seismic factors and hydraulic conductivity. The groundwater-level change, earthquake intensity, and vertical ground-surface displacement were found to show antipersistent tendencies while other factors showed the opposite. Higher correlations were found between hydraulic conductivity and groundwater-level change in aquifers 2–1 and 2–2, and between hydraulic conductivity and vertical ground-surface displacement in aquifer 3. Changes in porosities and hydraulic conductivity were evaluated in the main aquifers of the Choshuishi alluvial fan based on the data of hydrologic anomaly and the vertical ground-surface displacement. While both approaches show that the 1999 Chi-Chi earthquake has impacted the Choshuishi alluvial fan by reducing its porosity and hydraulic conductivity, these changes were not significant relative to natural variation in hydraulic conductivity.This revised version was published in May 2005 with correction to the rubric.     

节理岩体的分维特征及其工程地质意义

本文用分形理论,对节理网络分布和粗糙度曲线进行分形分析。结果表明,节理的空间分布和粗糙度曲线具自相似性;分维是一个表征岩体强度、岩体损伤程度、岩体质量及节理粗糙程度的几何参数,并可用于评价岩体稳定性、断裂体系活动性及划分风化卸荷带等。     

泥石流的分形特征及其意义

分析了泥石流流体和堆积物粒度分布的分形结构特征，其分维值介于２￣３之间，平均值分别为２．７１和２．６５左右。研究了泥石流沟水系的分形特征及其在不同观察尺度下分维的变化特征，结果表明，分维可作为描述泥石流粒度成分和泥石流沟水系的参数，反映了泥石流活动的形成演化特征，在此基础上，论述了分维的研究意义。     

Geomorphometry and fractal dimension of a riverine badland in Maharashtra

One of the most serious limitations in studying the surface morphometry of a badland landscape is the nonavailability of a very fine resolution data which is essential for such types of studies. Local relief of most of the badlands in India and also from other parts of the world exhibit limited relief amplitude, often within a few meters. The paper reports a case study carried out in a riverine badland formed along the Western Deccan Trap Region. An attempt has been made in the present paper to extract the morphometric variables of the landscape from the DEMs derived from a high resolution field generated data, because the accuracy of the DEM derived values are dependent on the pixel resolution of the DEM from which they are generated. The size of the pixel resolution should be fixed differently for different landscapes depending on the landscape process in the area. The local relief of the area is around 10 m and for such types of landscapes the topographical maps and also the web-available DEMs are of very coarse resolutions which are not suitable for the analysis. Therefore two well defined tributary catchments were chosen from the area under investigation and theodolite surveys were carried out, contours were generated with 10 cm interval, DEMs were derived by using Arc GIS software. SRTM (Shuttle Radar Topography Mission) 90 m resolution data were utilized to generate DEM for the whole basin. Hypsometric and the drainage basin parameters were extracted from these data by using the same software. Fractal dimension of the whole basin and the sample basins were also obtained for the same data. The morphometric data generated were used to understand the geomorphic processes operating in the area.     

两类花岗岩的分形比较

本文用分形结构因子比较了两类不同的花岗岩系列在矿物学、岩石化学和成矿关系等方面的差别。分形理论不但可从新的角度考察两类花岗岩的差别，而且为解决地质科学问题提供了新的思路和方法。     

Analysis of aftershock sequences in South and Southeastern Spain

A probabilistic modeling is used to analyze the spatio-temporal behavior of eleven aftershock sequences occurred in South and Southeastern Spain. This study focuses on the analysis of two seismicity parameters: the b-value of the frequency-magnitude distribution, and the p-value, explaining the temporal decay rate of aftershocks. The estimated b values range between 0.77 ± 0.05 and 1.18 ± 0.10 close to the typical b-values of the aftershock frequency-magnitude relationship b ≈ 1.0. The estimated p-values range between 0.75 ± 0.03 and 1.43 ± 0.10 showing broad regimes of the temporal decay of aftershocks. The modified Bath’s law used to analyze the energy partitioning, suggests that a large fraction of the accumulated energy is released in the mainshock and relatively small fraction of energy is released during aftershock sequence, for example 80% of the total energy is released during the Mula 1999 mainshock, 88% during Bullas 2002 mainshock and 87% during La Paca 2005 mainshock. The fractal dimension D₂ is estimated using the correlation integral, and then used to derive the slip ratio, as the ratio of the slip occurred on primary fault segment to the total slip. For example, we obtained a slip ratio equal to 71% for the Mula 1999 aftershock sequence, 61% for the Bullas 2002 event, 58% for the La Paca 2005 aftershock, 50% for the Lorca 2011 sequence and 63% for the sequence triggered by the Gador 2002 mainshock.Finally, the correlations between the fractal dimension, the b-value and the p-value is analyzed, and the Aki’s relation D = 3b/c is discussed as well.     

地震主压应力轴分布的分形特征研究

本文通过对全国许多地区大量的小震及中、强地震主压应力轴分布情况的详细研究，发现地震主压应力轴的分布具有分形结构特征，并满足幂函数关系式ｌｇＮ＝ａ＋ｂＪ，其特征值ｂ与分数维大致成反比，无标度区约为２°－８°。中强以上地震的前震序列的地震主压应力轴分布的特征值似乎明显比小震群活动的地震主压应力轴分布的特征值大。     

岩体裂隙网络分数维计算机模拟

岩体裂隙网络的研究是一个方兴未艾的课题,而用分形几何来研究岩体裂隙网络是一种行之有效的手段,本文将介绍由笔者编制的计算机裂隙网络分数维求解方法及程序,以达到快速、便捷而又准确地求解复杂网络的分维数。     

浑江断裂带及水系的分形特征和构造活动性研究

应用分开有几何学方法对浑江断裂带及水系进行了分形特征研究。计算结果表明，浑江断裂带具有较强的活动性，而且次级NNE向断层比NE和NW向断层活动性更强，结合地震活动属于 质地貌，构造应力场等方面的分析。探讨了该断裂带的活动性及区域新构造运动特征。