【摘要】：目前,隨著勘探目標(biāo)愈加復(fù)雜,傳統(tǒng)單一地球物理方法無法滿足當(dāng)前的勘探要求,并且受到地球物理反演問題多解性影響,使得綜合地球物理勘探之路勢在必行。聯(lián)合反演的目標(biāo)是獲得滿足不同地球物理數(shù)據(jù)的地球物理模型,因此,需要不同地球物理方法之間存在一定的聯(lián)系,而波速與密度之間的關(guān)系較為明顯,所以在聯(lián)合反演中,重震聯(lián)合反演的研究較多,本文研究二維界面的重震聯(lián)合反演。二維界面的重震聯(lián)合反演采用能夠較好反映界面信息的反射波與重力數(shù)據(jù)聯(lián)合。在重力正演方面,利用2.5D直立六面體剖面界面模型,進(jìn)行重力正演;在地震波走時正演方面,采用快速行進(jìn)法(FMM)分區(qū)多步方法,利用不等間距差分解決起伏觀測面或界面的地震反射波走時正演,并利用線性旅行時插值法(LTI)進(jìn)行了射線追蹤。在反演方面,分析了前人在聯(lián)合反演研究中使用的目標(biāo)函數(shù),通過分析認(rèn)為該目標(biāo)函數(shù)受重力異常和地震走時單位選取的影響較大,經(jīng)過研究得出聯(lián)合反演的目標(biāo)函數(shù)采用歸一化目標(biāo)函數(shù),解決了這一問題。利用理論模型測試了不同目標(biāo)函數(shù)的反演效果以及不同權(quán)重因子下的反演結(jié)果。理論模型測試結(jié)果表明,本文提出的歸一化目標(biāo)函數(shù)基本不受重力異常和地震走時單位選取的影響,而且這一目標(biāo)函數(shù)受權(quán)重因子的影響也較小。同時為了提高計(jì)算效率,從反演計(jì)算量最大的正演計(jì)算入手,引入并行運(yùn)算,大大提高了反演的計(jì)算效率。最后,將該方法用于M?re陸緣地區(qū)的莫霍面深度反演,利用衛(wèi)星重力數(shù)據(jù)和海底高頻地震儀(OBS)莫霍面反射波走時進(jìn)行聯(lián)合反演,得到了莫霍面深度。通過應(yīng)用研究認(rèn)為該方法具有一定的實(shí)用性。
[Abstract]:At present, with the increasing complexity of exploration targets, the traditional single geophysical method can not meet the current exploration requirements, and is affected by the multiple solutions of geophysical inversion problems, which makes the road of comprehensive geophysical exploration imperative. The goal of joint inversion is to obtain geophysical models satisfying different geophysical data. Therefore, there is a certain relationship between different geophysical methods, and the relationship between wave velocity and density is more obvious, so in joint inversion, There are many studies on joint inversion of heavy earthquakes. In this paper, the joint inversion of heavy earthquakes at two-dimensional interface is studied. In the joint inversion of heavy earthquakes at the two-dimensional interface, the reflected waves and gravity data which can better reflect the interface information are combined. In the aspect of gravity forward modeling, 2.5D vertical hexahedral section interface model is used to carry out gravity forward modeling. In the aspect of forward modeling of seismic wave travel time, the fast forward method (FMM) partition multi-step method is used to solve the travel time forward modeling of seismic reflected wave on undulating observation surface or interface by using unequal spacing difference. The linear travel time interpolation method (LTI) is used for ray tracing. In the aspect of inversion, the objective function used in the joint inversion research is analyzed, and it is considered that the objective function is greatly affected by gravity anomaly and seismic travel time unit selection. Through the research, it is concluded that the objective function of joint inversion adopts normalized objective function, which solves this problem. The inversion effect of different objective functions and the inversion results under different weight factors are tested by using the theoretical model. The test results of the theoretical model show that the normalized objective function proposed in this paper is basically not affected by gravity anomaly and seismic travel time unit selection, and this objective function is less affected by the weight factor. At the same time, in order to improve the computational efficiency, the parallel operation is introduced from the forward calculation with the largest amount of inversion computation, which greatly improves the computational efficiency of inversion. Finally, the method is applied to the Moho surface depth inversion in the M?re continental margin area, and the Moho surface depth is obtained by using the satellite gravity data and the travel time of the reflected wave on the (OBS) Moho surface of the seafloor high frequency seismograph. Through the application research, it is considered that the method has certain practicability.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：P631

【參考文獻(xiàn)】

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本文編號：2475580