地震折射波的虚拟射线理论及其应用

本文提出了一种地震折射液的虚拟射线理论,根据该理论,只要已知地表层的速度,即可直接由折射波信息提取地震参数,从而可实现折射界面的反演。 文中通过实际介质模型的计算机实验结果,验证了该理论的正确性。     

High parallelization efficiency in barotropic-mode computation of ocean models based on multi-grid boundary ghost area

In general, barotropic-mode computation requires the largest communication time in ocean models because of its iterative nature, when parallel computation is performed based on regional partitioning. In this study, reduction in the overhead time included in the communication in the parallel computation of the barotropic mode is considered to achieve a high parallelization efficiency of ocean models. We verify that the reduction in the communication frequency based on the multi-grid boundary ghost area reduces the total communication time. We find that this is because the sum of several kinds of overhead time for communication occupies a fairly large part of the total communication time. We discuss the trade-off between the decrease in communication time and the increase in computation time due to increased boundary area in such cases, leading to a determination of a suitable width of the multi-grid boundary that minimizes the total required time. We also discuss the efficiencies of the one- and two-dimensional partitioning of the model domain, when a multi-grid boundary is used. In general, two-dimensional partitioning is more efficient than one-dimensional for large partitioning numbers.     

深层地震勘探激发井深探讨

深层地震勘探野外资料采集的关键是在保证原始资料一定信噪比的基础上,同时兼顾分辨率,激发井深是决定资料品质的重要因素之一。通过对虚反射滤波作用分析,提出了充分利用虚反射能量设计最佳激发井深,增强下传地震波能量的采集方法。理论分析和试验资料表明,在高速层下4～7m的最佳激发岩性深度是深层勘探的理想井深。     

海底电缆鬼波压制及陷频补偿方法研究

受到海底、自由表面等强反射界面的影响, 在海底电缆采集的地震资料中鬼波干扰往往非常发育, 在频谱中表现为明显的陷频现象, 严重影响地震剖面的质量, 给后期的处理解释带来困难。为克服这一困难, 根据海底电缆双检(陆检和水检)对下行波场的不同响应, 在深入研究伪多道匹配滤波技术的基础上提出了伪多道双检合成方法。与传统的求取反射系数的双检合成方法不同, 该方法完全数据驱动。在合成数据和渤海地震资料的实际应用中, 鬼波成分得到了明显的压制, 同时拓宽频带, 补偿陷频, 证明了该方法的有效性。     

城市新区作为“家”的表征与实践——以鄂尔多斯康巴什新区为例

本文基于表征与非表征的研究视角,分析了以鄂尔多斯康巴什为代表的中国城市新区作为“家”的表征与实践过程。研究发现：针对康巴什新区,外部媒介与地方政府以表征手段建构了截然不同的“家”的意象。其中,BBC、Times等外媒将康巴什新区描绘成充满荒凉景观的“鬼城”和不健康的中国城市居住空间,而在地方政府的重构中,康巴什新区则充满了生态栖居必备的城市景观并成为了先进的城市文化空间。而作为“家”中的居住者,康巴什居民“家”的营建经历了从陌生到认同的渐进过程,这一过程包含了日常生活实践中的空间转换与情感边界的构建。不同行动者共同塑造了康巴什新区多元的、充满矛盾意义的“家”的空间身份。本文旨在丰富中国快速城市化背景下“家”的地理学研究视角与类型,回应“鬼城”话语对地方政府主导的城市化“无家”的质疑,亦是城市新区社会文化研究的有益拓展与补充。     

Rewriting the book of the city: on old signs,new technologies,and reinventing Adelaide

Can a sense of ownership over constantly changing urban places be generated through pedestrian exploration and everyday digital media practice? This paper begins with the author’s visit to the city of Adelaide, where a chance encounter – an intriguing sign painted on the wall of a city building – led to a hunt through the city for ghost signs, the remnants of old hand-painted advertisements. This spontaneous activity, combined with the online exploration and image sharing that followed, generated a renewed feeling of connection to, and ownership over, an erstwhile familiar locale. The experience is analysed through the work of theorists investigating change and belonging in modern cities including Guy Debord, Doreen Massey, Michel de Certeau, Andreas Huyssen, and Mark Crinson, as well as the contemporary growth in both politically inspired urban exploring (“Urbex” or “place hacking”) and the digital documentation and sharing of ghost signs and other urban ephemera.     

海上地震虚反射相位剔除法反褶积

在分析了虚反射的形成机制及其滤波器频谱特性的基础上，提出了一种在频率域剔除地震鬼波的新方法，该方法直接剔除的是虚反射滤波器相位谱的影响，而对于振幅谱，则是通过同时消除虚反射与地震子波两者共同的影响来拓宽地震记录的有效频谱，处理过程自动避免了鬼波滤波器的“零值点”问题，其最终结果是以获取反射生活费数为期望输出，因此，该方法在消除鬼波的同时可进一步提高地震剖而后 分辨率。实验表明，本文所提出的反褶积方法具有较好的容噪能力。且在鬼波延迟时以及虚反射界面反射系数存在一定误差的情况下仍能获得令人满意的处理结果。     

RESEARCH ON TIME-DISTANCE INTERPRETATION OF MULTIPLES AND GHOSTS BASED ON MARINE SEISMIC DATA

Currently, the study on the active fault in the land areas is relatively mature, while there is still lack of detection and research on active faults in the sea areas. Marine exploration, which is different from land areas, has a prominent problem due to the existence of strong reflecting interfaces such as water surface and seafloor in the sea, thus the recording is often accompanied by interference of multiples on seafloor reflections. In addition, because of the characteristics of marine seismic exploration, the source exciting in the water and the geophone receiving in the water, ghost wave usually can be recorded simultaneously during the reflected wave propagation. This phenomenon makes it difficult to distinguish the effective waves and the noise, and has always plagued the data and seriously affects the quality of records. In the offshore and other regions of complex structures, such as inclined interfaces, it is difficult to eliminate the interference of multiples accurately by traditional multiples suppression methods, which are based on the horizontal interface assumption. This paper combines the sea area seismic data and its acquisition method, uses simplified model to simulate the multiples based on the time-distance analysis of multiples and their ghost wave in inclined interface. The time-distance characteristics of the multiples and their ghost waves from different interfaces(including the inclined interface)are obtained, and they are consistent with the actual records. The multiples time-distance simulation can help to distinguish the causes of reflected waves, summarize the multiple-wave time-distance characteristics from different interfaces(including inclined interfaces), and analyze the relationship between the characteristics of multiple waves and primary waves. In particular, this simulation has a significant effect on characterizing the internal multiples that are difficult to identify due to inconspicuous periodicity and the multiples of the inclined interface which present the phenomenon that the vertex of the time-distance curve is shifted. On this basis, relying on the time-distance analysis of ghost wave, we analyze the travel time difference characteristics between reflected waves and their accompanying ghost waves. The differences of the travel time characteristics of different orders ghost wave and reflected wave are summarized and the symmetry of the travel time difference between inclined interface and horizontal interface of ghost waves and reflected waves is analyzed. We simulate the distraction of the ghost wave event with the event of the reflected wave and analyze the influence of the ghost wave on the sea area seismic records. These results can improve the practical interpretation of seismic data. At last, the time-distance information is used to synthesize sea area seismic records, which can help us carry out the effective data processing and understand the characteristics of the time-distance and velocity of multiples in different interfaces and the layer artifact caused by multiples. This study combines the time-distance simulation of multiples and their ghost wave with conventional seismic data processing to analyze the pre-stack and post-stack features of multiple waves and their ghost waves in the seismic records of the sea area. The results of this study are conducive to the effective identification of multiples in seismic records in the sea, provide a theoretical basis for multi-wave suppression and prediction, and may facilitate the future study of sea-area seismic activity detection.     

一种新型三维水流数值模型

以不可压缩流体的N-S方程为基本控制方程,用快速粒子level set方法(FPLS)追踪自由表面,提出了一种新的三维水流数值模型。在自由表面处应用虚拟压力法来封闭压力泊松方程,同时用速度等值外插的方法构造自由表面外侧的虚拟速度分布。通过模拟水波振荡、水柱崩塌、水滴滴落和空箱注水过程证明了模型的有效性。