利用水库大容量非调制气枪阵列进行区域尺度地下结构探测和监测

发布时间：2018-05-18 00:14

本文选题：区域尺度 + 主动探测　；参考：《中国地震局地球物理研究所》2014年博士论文

【摘要】：大量的地震学证据表明地震的发生与深部的结构密切相关。除去与地下结构相关,地震的发生更重要的是与地下的结构和状态的变化有关。地震通常被认为是由于地下应力的积累和释放造成的,因此应力状态及其变化是地震发生的关键因素。如果我们能够对地震危险区(例如断层带、各级速度块体的边界以及高低速层的过渡带)地下的应力状态进行连续监测,将会有助于我们判断这个地区发生地震灾害的危险性。但是我们并没有方法能够对深部孕震区的应力状态进行直接测量,室内岩石物理实验表明岩石的波速会随着加载压力的变化而变化(声弹性),因此我们就可以通过测量穿过深部孕震区的地震波的波速的变化来监测地下应力的变化。对区域尺度深部结构的探测和监测还不只是减轻地震等自然灾害的需要,而且也是开发开采油气矿产资源的需要。为了进行区域尺度地下结构的探测和监测,我们采用两种震源：水库大容量非调制气枪阵列震源和背景噪声震源。首先是水库大容量非调制气枪阵列的方法。由于通常用于区域尺度地下结构探测的天然地震方法存在空间和时间上的局限性以及地震定位精度差的问题,而通常用于区域尺度地下结构探测的炸药等人工震源方法又存在破坏环境重复性差等问题,都不是特别适合区域尺度地下结构的探测和监测。为此,我们实验室一直在探索新的区域尺度地下结构探测和监测的方法。我们实验室通过多次试验发现水库大容量非调制气枪阵列具有频率低、传播距离远、重复性好以及对环境无破坏等特点,非常适合陆地区域尺度地下结构的探测和监测。对于震源的认识是进行结构及其变化探测研究的第一步。由于水库大容量非调制气枪阵列是在陆地水库中进行激发,相比于在海洋中进行激发的气枪阵列,陆地水库水域面积更小,水深更浅,气枪阵列与水库的相互作用更为复杂,气枪阵列与陆地水库共同构成了一个震源系统。目前对于这种震源系统的研究还很少。我们根据Rayleigh-Plesset气泡震荡方程以及流体中的动量方程和连续性方程,构建了一个适用于远场气枪地震信号的作用于液固界面的单力震源模型。之后我们介绍了水库大容量非调制气枪阵列在区域尺度地下波速变化监测中的应用。为了对地震频发的滇西地区,特别是位于其中的红河和程海两大断裂带地下的波速变化进行监测,利用水库大容量非调制气枪阵列,我们实验室于2011年4月在云南省大理州宾川县的大银甸水库建立了世界上第一个气枪地震信号发射台站。由于水库大容量非调制气枪阵列的优越性能,宾川气枪地震信号发射台站可以连续不断地向地下发射传播距离远、重复性高的地震信号。利用宾川气枪地震信号发射台站激发的地震信号,我们就可以对滇西地区的地下波速变化进行监测。虽然目前我们尚处于数据积累的阶段,我们利用在宾川气枪地震信号发射台站进行的6次激发试验,研究了激发条件(激发压力、沉放深度和水库水位)对水库大容量非调制气枪阵列激发地震信号的影响。这对于以后我们提高这类气枪地震信号发射台站的性能以及进行波速变化研究都有重要意义。接下来我们介绍了水库大容量非调制气枪阵列在区域尺度地下结构探测中的应用。利用2006年我们实验室在河北省遵化市上关湖水库进行的大容量非调制气枪阵列产生的地震数据,我们采用波形拟合的方法,研究了燕山隆起带南部地区地下的一维P波、S波、泊松比以及波速比结构。我们发现该地区的地壳厚度约为33km,上中地壳的泊松比值偏低,可能以长英质的酸性岩石为主,下地壳以及上地幔顶部泊松比值稍高,可能以铁镁质的基性岩石或中性岩石为主。并且在该地区的上下地壳各存在一个P波和S波的低速层,并且这两个低速层还对应着泊松比和波速比的高值区。上地壳的低速层可能是流体作用的结果,而下地壳的低速层则可能是由于部分熔融造成的。最后我们介绍利用尾波理论进行地下波速变化成像研究。尾波是多重散射波,相比于直达波,它对地下介质变化更为敏感。利用尾波可以测量地下微弱的波速变化。水库地区,水库水位的变化会引起地表载荷的变化,进而引起地下应力和应变的变化,是定量研究地下应力和应变变化与地下波速变化关系的理想区域。由于进行本研究时,我们的气枪地震信号发射台站连续激发的时间还比较短。我们利用由架设在云南省大理州宾川县大银甸水库周围的16个流动地震台站记录到的背景噪声相关得到的连续经验格林函数的尾波部分,我们测量了这些台站间的波速变化,并且利用敏感核的方法反演了这个地区的波速变化的分布。我们发现可能只有距离水库很近的地区的地下波速变化可能是由于水库水位的变化造成的,而其它地区的波速变化则可能是由于地下水位的变化导致的。
[Abstract]:A large number of Seismological Evidence indicates that the occurrence of an earthquake is closely related to the structure of the deep. In relation to the underground structure, the occurrence of the earthquake is more important than the change in the structure and state of the underground. The earthquake is usually considered to be caused by the accumulation and release of the underground stress, because the stress state and its change are the key to the earthquake. Key factors. If we can continuously monitor the stress state of the earthquake zone (such as the fault zone, the boundary of the velocity block at all levels and the transition zone of the high and low velocity layer), it will help us to judge the danger of the earthquake in this area. But we have no way to stress the stress state in the deep seismogenic area. In a direct measurement, laboratory petrophysics experiments show that the velocity of the rock changes with the change of loading pressure (acoustic elasticity), so we can monitor the change of the underground stress by measuring the wave velocity that passes through the seismic waves in the deep seismogenic area. Such as natural disasters need, but also the development and exploitation of oil and gas mineral resources needs.
In order to detect and monitor the subsurface structure of the region, we adopt two sources: the source of the large capacity non modulated air gun array and the source of the background noise. First, the method of the reservoir large capacity non modulation air gun array. The limitation and the poor accuracy of the seismic location, and the artificial source method, which is usually used in the detection of the subsurface structure of the regional scale, also have the problems of the poor repeatability of the environment, which are not especially suitable for the detection and monitoring of the subsurface structure of the regional scale. Therefore, our laboratory has been exploring the new regional scale underground structure exploration. Through several experiments, we found that the large capacity non modulation gas gun array of the reservoir has the characteristics of low frequency, long propagation distance, good repeatability and no damage to the environment. It is very suitable for the detection and monitoring of the ground structure of the land.
The understanding of the source is the first step in the study of the structure and its change detection. Because the large capacity non modulation air gun array is excited in the land reservoir, the water area of the land reservoir is smaller, the water depth is shallower, the interaction of the gas gun array and the reservoir is more complex, and the gas gun is more complex than the air gun array in the land reservoir. A source system is formed together with the land reservoir. At present, the research on the source system is very few. Based on the Rayleigh-Plesset bubble oscillation equation and the momentum equation in the fluid and the continuity equation, a single force source model for the liquid solid interface is constructed for the remote field air gun seismic signal.
Then we introduce the application of the large capacity non modulation gas gun array in the monitoring of the variation of the velocity variation in the regional scale underground. In order to monitor the wave velocity changes in the west of Yunnan, especially the two major fault zones in the Honghe and Cheng Hai fault zones, the large capacity non modulation gas gun array of the reservoir is used in our laboratory at 2011. In April, the first gas gun seismic signal station was set up in the grand sildian reservoir in Binchuan County, Dali, Yunnan province. Due to the superior performance of the large capacity non modulated gas gun array, the Binchuan gas gun seismic signal transmitting station can transmit the seismic signals which are far away from the ground and have high repeatability to transmit to the underground station. The use of Binchuan is to use the seismic signal. We can monitor the change of the ground wave velocity in the West Yunnan. Although we are still in the stage of data accumulation, we have studied the excitation conditions (the excitation pressure, the depth of the sink and the reservoir), using the 6 excitation tests at the Binchuan gas gun seismic signal station. The effect of the water level on the seismic signal excited by the large capacity non modulated air gun array is of great significance to the improvement of the performance of this type of air gun seismic signal station and the study of the wave velocity change.
Then we introduce the application of the large capacity non modulation gas gun array in the exploration of the regional scale underground structure. Using the seismic data produced by the large capacity non modulation air gun array in the Shangguan Lake Reservoir in Zunhua, Hebei Province in 2006, we have studied the southern part of the Yanshan uplift zone by using the method of waveform fitting. One dimension P wave, S wave, Poisson's ratio and wave velocity ratio structure are found in the region. We found that the crust thickness of the region is about 33km, the Poisson ratio of the upper middle crust is low and may be dominated by the acidity rocks of the felsic, and the Poisson ratio at the top of the lower crust and the upper mantle is slightly higher, and may be dominated by magnesia based or neutral rocks. There is a low velocity layer of P wave and S wave in the upper and lower crust of the region, and the two low velocity layers also correspond to the high value zone of the Poisson's ratio and the wave speed ratio. The low velocity layer of the upper crust may be the result of fluid action, while the low velocity layer in the lower crust may be caused by partial melting.
Finally, we introduce the study of the change imaging of the underground wave velocity using the tail wave theory. The wake wave is a multiple scattering wave. Compared with the direct wave, it is more sensitive to the change of the underground medium. The change of the weak wave velocity in the underground can be measured by the wake wave. The reservoir area, the reservoir water level changes will cause the change of the surface load, and then cause the underground stress and the underground stress. The change of strain is an ideal area for quantitative study of the relationship between the change of underground stress and strain and the change of the velocity of the underground wave. Because of this study, the time of continuous excitation of our gas gun seismic signal transmitting station is still short. We use 16 mobile seismic stations around the Dayin reservoir in Binchuan County, Dali, Yunnan province. We recorded the wake part of the continuous empirical Green function obtained by the background noise related to the background noise. We measured the wave velocity changes between these stations, and used the sensitive core method to retrieve the distribution of wave velocity in this area. We found that the change of the velocity of the wave velocity in the area near the reservoir may be due to the reservoir water. The change of wave velocity in other areas may be caused by the change of groundwater level.
【学位授予单位】：中国地震局地球物理研究所
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV698.1;P631.4

【参考文献】