Quantitative analysis of land surface topography

Land surface topography significantly affects the processes of runoff and erosion. A system which determines slope, aspect, and curvature in both the down-slope and across-slope directions is developed for an altitude matrix. Also, the upslope drainage area and maximum drainage distance are determined for every point within the altitude matrix. A FORTRAN 66 program performs the analysis.     

The perturbation method in elastic wave scattering

Methods of theoretical study in seismic wave scattering are reviewed with the emphasis on the perturbation method. Detailed analysis for weak scattering using Born approximation is given. For elastic random media, the mean square amplitudes of scattered waves are derived using a new approach by working directly in the spectrum domain. The conditions for the scalar wave approximation are obtained. The problem of sensitivity of fore- and backscattering to heterogeneities with different scales and properties (velocity or impedance) is discussed.     

综合概率法及其在表征潜在震源区时空不均匀性上的应用

本文由强地震的重复性、中小地震活动图象与强震发生的时空关系、破裂空段、大地震的减震性及华北5—10年危险性估计入手,利用综合概率法,讨论描述潜在震源区时空不均匀性的途经与方法。并以河北省北部的部份潜在震源区为例,确定了描述这些潜在震源区时空不均匀性的加权系数,并结合由韦布尔分布确定的年发生率,得出了可应用于危险性分析的不同的年发生率     

Effect of slip rate on stress drop

Recent observations made by Kanamori and Allen about earthquake recurrence time and average stress drop revealed a very interesting relation: earthquakes with longer recurrence times have higher average stress drops. They attributed the difference in stress drop to the difference in long-term average slip rate. To interpret their result in terms of the healing effect, we simulated earthquake recurrence with a one-dimensional mass-spring model, incorporating a recently developed rate-and-state dependent friction law for different loading rates and heterogeneous strength distributions. We first calculated the stress drop and recurrence time as functions of loading rate for a homogenous fault model. We found that the stress drop increases up to 30% when the loading rate decreases from 10 cm/yr to 0.01 mm/yr. Thus, the observed great variability of stress drop, from a few bars to a few hundred bars, which is obtained by replotting the data of Kanamori and Allen in the form of stress drop versus long-term slip rate, may not be attributable to the healing effect alone. Our numerical simulation shows that the variability may be due primarily to the spatial heterogeneity of strength on the fault. Our simulation also suggests that of the two empirical laws that were inferred from the same laboratory friction data, called the power law and the logarithmic law by Shimamoto and Logan, the former can explain the observed relation between stress drop and slip rate better than can the latter, at least for strike-slip fault. The logarithmic law is an earlier and simpler version of the rate-state-dependent friction law.     

Effect of waterwashing on light ends compositional heterogeneity

A number of experiments have been carried out to study in the laboratory the effects of waterwashing on light ends composition. The experimental data were then compared with the results of a simple numerical model. Both approaches confirm the fast removal of the light aromatics by the flushing water and the very slow alteration of the C₁₀₊ compounds. The experimental results also indicate that the normal paraffins are removed faster than the cycloalkanes which is not in agreement with their respective solubility data. the simulations show that, over geological time, compounds such as benzene and toluene should be completely absent in an oil column which is not the case. Therefore, it is likely that in nature oil-water interactions are not as effective as one could imagine, which has implications for oil migration, as well as for the understanding of hydrodynamism phenomena in oil pools.     

地形通行性能的研究

本文从计算机地形分析的角度，研究了地形通行性能分析的方法与步骤，对涉及的地形因素，采用调研和试验得到的数据，建立了数学模型。     

蚀变作用的多原岩系统及质量平衡

介绍了造成岩石地球化学不均匀性的原因，主要有测量误差、闭合问题及岩石学方面的控制等。各有其不同的研究和解决方法。对于蚀变岩的多原岩系统，常用不相容高场强元素（HFSE）来描述岩石性质，用其作为监视器，可作出各相容元素（或成分）的分异线；用不活动元素蚀变线与分异线的产点来确定原始成分，并在此基础上进行蚀变岩质量变化的计算。     

Experimental examination on the heterogeneity parameter C_v of earthquake precursors

Introduction Many earthquake cases indicate that there exists obvious heterogeneity in temporal-spatial distribution of earthquake precursors (FENG, 1983; MEI, et al, 1993). Therefore, it is very crucial for the study of earthquake prediction to describe the heterogeneity in temporal-spatial distribution of earthquake precursors and to understand its physical mechanism. Up to now, a lot of useful researches have been done in this field. Recently, WANG, et al (1999) and CHEN, et al (2000)…     

Seismic monitoring of explosions: a method to extract information on the isotropic component of the seismic source

The design of a monitoring system for detecting explosions is a very topical problem, both for routine data processing at seismological observatories as well as for the monitoring of a Comprehensive Test Ban Treaty. In this framework it is desirable to have the possibility to quantify the presence of the isotropic component in the seismic source. For this purpose a method is presented, which is based on waveform inversion for the full moment tensor retrieval. The method inverts either full waveforms or separate seismic phases and returns the mechanism and time history of a point source. Moreover, it allows to redefine the hypocentral depth of the event and, in a simplistic way, to optimize the structural model as well. In order to model strong laterally heterogeneous structures, different pairs of structural models can be used for each source-receiver path. The source is decomposed into a volumetric part (V), representing an explosive or implosive component, and into a deviatoric part, containing both the double couple (DC) and the compensated linear vector dipole (CLVD) components. The method is applied to an area in central Switzerland and to the network of the Swiss Seismological Service. The events of interest include both earthquakes and explosions. Despite some modelling inadequacies of the source-time function, the explosions can be well identified with the inverted isotropic component in the source, as long as the number of stations used for the inversion is larger than three. The results of the inversion are better for large epicenter-station distances of the order of 40–90 km.