活断层上均匀盖层中氡浓度分布的数值模拟及反演拟合

Based on the convection and diffusion mechanisms of radon migration, in this paper we deduce the two-dimensional differential equation for radon transportation in the overburden above active fault zones with an unlimited extension along the strike. Making use of the finite difference method, the radon concentration distribution in the overburden above active faults is calculated and modeled. The active fault zone parameters, such as the depth and the width of the fault zone, and the value of radon concentration, can be inverted from the measured radon concentration curve. These realize quantitative interpretation for radon concentration anomalies. The inversion results are in good agreement with the actual fault zone parameters.     

均匀覆盖层中氡迁移的数值模拟

氡能从地下深部运移到地表,可带来反映地下地质状态的信息.本文以氡在均匀覆盖层中的迁移过程为对流-扩散方式作为理论基础,推导了二维氡浓度微分方程,用有限差分方法计算了无限氡源层、有限单氡源层、有限双氡源层在均匀覆盖层中氡浓度的数值解,以二维断面的形式展示了氡的分布,其结果与野外实测相符.     

土壤氡在海口活断层的试验测量.

使用德国脉冲电离室测氡仪,在海口已知全新世活断层上进行了一条剖面土壤氡试验测量,测量点距为10m,异常点附近加密为5m,测量结果显示高值异常点位与断层位置相吻合,说明仪器测量质量和效果较高,测量装置合理,为今后工作积累了经验.     

断层气氡在不同类型覆盖层中 迁移规律的数值模拟

断层气氡浓度是探测断层位置与断层活动性的一种有效手段. 该文基于Abdoh和Pilkington提出的氡迁移二维偏微分方程与相应的边界条件, 建立内部含裂隙、 裂隙系-断层带和非均质等3种覆盖层物理模型, 在Matlab平台上运用偏微分工具箱(pdetool)与非线性求解函数(pdenonlin), 对模型求解以及模拟覆盖层中氡迁移. 通过对3种模型的模拟结果分析, 分别解释了地表氡异常点与断层带位置不同步现象, 覆盖层厚度对氡浓度曲线形状的影响, 以及土壤结构性质对氡异常强度和异常形态的影响.     

郯庐断裂带宿迁段合欢路土壤氡分布特征与迁移特征的数值模拟

沿郯庐断裂带宿迁段合欢路布设土壤氡测线并对测得的数据进行分析研究,结果表明研究区域内土壤氡探测结果对断裂带位置、断层类型和特征有较好的指示性。在已知场地地质构造参数、地层岩性特征的基础上,建立土壤氡迁移模型。建立模型时识别了断裂类型和覆盖层分层特征,并讨论了断层内部结构与氡浓度取值,使模型与实际情况相等。数值模拟结果印证了土壤氡异常峰区间在圈定断裂位置和断层破碎带中的重要作用,揭示了氡在不同覆盖层中的迁移速度,并定量解释了合欢路场地断层土壤氡异常的成因。     

海河隐伏活断层探测中土壤气氡和气汞测量及其结果

在海河隐伏断裂的探测中,利用FD-3017RaA测氡仪和XG-4型测汞仪开展了土壤气氡和土壤气汞的测量工作。根据12条断层气测线的测量结果,结合人工地震探测资料,对断层气异常位置与断层位置的关系进行了分析;运用断层气异常强度与断层活动性的关系对海河断裂的活动性进行了研究,给出了海河断裂天津段的位置和活动性分段。研究结果表明,断层气方法不仅能给出断层的初步位置,而且能够用于断层的活动性初步分段,但断层气方法所给出的断层位置应是一个条带。经与人工地震探测结果对比分析,断裂位于这个条带内;根据土壤气氡测量结果,可将海河断裂分为东、西两段,且东段的活动性要强于西段。这种强、弱之分仅是一种相对结果,在判定断层是否为活断层方面还存在一定困难     

聊古一井数字化氡与模拟水氡观测资料的对比评价

数字化氡在聊古一井投入观测已近4年, 与模拟水氡观测相比, 具有采样率高, 数字传输、保存和资料处理快捷方便, 人为观测误差少的优点, 从而使氡的信息量大大增加, 为捕捉地震短临异常信息提供了有利条件。对数字化氡与模拟水氡同期观测资料的对比分析结果表明, 二者的变化趋势、方差及均值变化均不一致, 数字化氡与模拟水氡观测的物理含义不同,是一种新的测项, 尚不能完全替代原有的模拟水氡观测; 数字化氡在反映地震短临异常方面优于模拟水氡; 气水分离装置(脱气装置)是实现氡数字化观测的重要基础环节, 对于获取真实可靠的观测结果具有重要作用。     

土壤氡浓度测量在广州市岩溶地面塌陷、地面沉降地质灾害调查中的应用

由于受大型地下工程施工大量抽排地下水的影响,广州市大坦沙和金沙洲先后发生了大规模岩溶地面塌陷、地面沉降地质灾害,为查明区内岩溶发育和断裂带的分布情况,综合运用土壤氡浓度测量、高密度电法、浅层地震反射波、弹性波CT和地质雷达进行探则.由于受各种管线、电磁和震动的干扰,在城市开展电法、磁法、浅层地震等受到限制,而土壤氡浓度测量具有不受地电、地磁和震动干扰的优点.本文以土壤氡浓度测量在广州市金沙洲和大坦沙岩溶地面塌陷、地面沉降地质灾害应用为例,说明了土壤氡浓度测量机理、方法技术和影响因素,结果表明土壤氡浓度测量在广州市金沙洲和大坦沙岩溶地面塌陷、地面沉降地质灾害调查中取得了显著的效果,为广州市金沙洲和大坦沙地质灾害防治提供了基础资料.     

Numerical analysis model of horizontal displacement of active faults

In this paper, a numerical model was presented for interpreting the movement feature of an active fault zone. This model was based on the analytic solution, given by Crouch (Crouch, 1976), for the problem of displacement discontinuity in an infinite elastic solid, making full use of geodetic and geological data and it was constructed by the boundary element method. A numerous test computation shows that if you want to catch the possible seismic precursor from the displacement’s vector, you have to associate the computation with geological survey in a deep going way, otherwise you would fail in your propose. This method is valid for analysing the zone of strike-slip fault and it has some values for dealing with other analogous problems. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 153–158, 1993.     

Measurement of radon gas on major faults in California,USA

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Numerical simulation on the influences of Wenchuan earthquake on the surrounding faults

On 12 May 2008, the devastating Wenchuan earthquake struck the Longmenshan fault zone, which comprised the eastern margin of the Tibetan Plateau, and this fault zone was predominantly a convergent boundary with a right-lateral strike-slip component. After such a large-magnitude earthquake, it was crucial to analyze the influences of the earthquake on the surrounding faults and the potential seismic activity. In this paper, a complex viscoelastic model of western Sichuan and eastern Tibet regions was constructed including the topography. Based on the findings of co-seismic static slip distribution, we calculated the stress change caused by the Wenchuan earthquake with the post-seismic relaxation into consideration. Our preliminary results indicated that: (1) The tectonic stressing rate was relatively high in Kunlun mountain pass-Jiangcuo, Ganzi-Yushu, Xianshuihe and Zemuhe faults; while in the east Kunlun and Longriba was medium; also the value was less in the Minjiang, Longmenshan, Anninghe and Huya faults. As to the Longmenshan fault, the value was 0.28×10^-3 MPa/a to 0.35×10^-3 MPa/a, which is coincident with the previous long recurrence interval of Wenchuan earthquake; (2) The Wenchuan earthquake not only caused the Coulomb stress decrease in the source region, but also the stress increase in the two terminals, especially the northeastern segment, which is comparatively consistent with the aftershock distribution. Meanwhile, the high concentration areas of the static slip distribution were corresponding to the Coulomb stress reductions; (3) The Coulomb stress change caused by Wenchuan earthquake showed significant increase on five major faults, which were northwestern segment of Xianshuihe fault, eastern Kunlun fault, Longriba fault, Minjiang fault and Huya fault respectively; also the Coulomb stress on the fault plane of the Yushu earthquake was faintly increased; (4) We defined the recurrence interval as the time needed to accumulate the magnitude of the stress drop, and the recurrence interval of Wenchuan earthquake was estimated about 1 714 a to 2 143 a correspondingly.     

生产油井井下温度场数值模拟分析

An improved numerical simulation method is presented to calculate the downhole temperature distribution for multiple pay zones in producing oil wells. Based on hydrodynamics and heat transfer theory, a 2-D temperature field model in cylindrical coordinates is developed. In the model, we considered general heat conduction as well as the heat convection due to fluid flow from porous formation to the borehole. We also take into account the fluid velocity variation in the wellbore due to multiple pay zones. We present coupled boundary conditions at the interfaces between the wellbore and adjacent formation, the wellbore and pay zone, and the pay zone and adjacent formation. Finally, an alternating direction implicit difference method （ADI） is used to solve the temperature model for the downhole temperature distribution. The comparison of modeled temperature curve with actual temperature log indicates that simulation result is in general quite similar to the actual temperature log. We found that the total production rate, production time, porosity, thickness of pay zones, and geothermal gradient, all have effects on the downhole temperature distribution.     

鲜水河断裂带的地震模拟

本文运用由弹簧—滑块模型来模拟走滑断层的地震活动,讨论了模型中断层强度、断层滑块间弹簧强度、滑块与驱动盘之间片簧强度、滑块摩擦力的影响,以及初始条件敏感性。并以我国最为典型的一条走滑断层———鲜水河断裂带为例,运用试错法调整模型参数以使发生的地震最大限度地逼近实际发生的地震,并利用最终结果讨论了鲜水河断裂带今后的活动性。     

水氡浓度和环境参数的分层神经网络研究

采用分层神经网络（LNN）分析地下水的氡浓度,试图给出氡浓度和环境参数之间的函数关系。由于环境（例如：降雨量）对水氡浓度的影响可能是非线性的,与目前时间脉冲响应线性计算方法相比,该方法能够较准确的估计环境参数造成的氡浓度变化。