本文選題：青藏高原　切入點：接收函數(shù)　出處：《成都理工大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：青藏高原的隆升和擴(kuò)張在長期以來一直是地球科學(xué)界的熱點問題之一。科學(xué)家們提出了許多不同的模型來解釋青藏高原的變形機(jī)制,而近年來剛性地殼塊體沿大型走滑斷層的側(cè)向擠出與中下地殼的粘性物質(zhì)管道流則是爭論的焦點。剛性地殼模型認(rèn)為斷層扮演了關(guān)鍵角色,而下地殼流模型認(rèn)為下地殼從上地殼和上地幔解耦。本文搜集了四川地震臺網(wǎng)記錄的龍門山斷裂帶2008-2014年3級以上的地震波形資料,通過矩張量反演獲取了1491個地震震源機(jī)制解。此外,本文還搜集了研究區(qū)內(nèi)在龍門山地區(qū)以外發(fā)生的695個地震震源機(jī)制解。根據(jù)震源機(jī)制解的斷層面參數(shù),本文采用阻尼線性反演技術(shù)獲取了研究區(qū)內(nèi)高分辨率的構(gòu)造應(yīng)力場。同時,本文搜集了研究區(qū)內(nèi)密集的寬頻帶流動臺站記錄的地震波形資料,分別采用接收函數(shù)集分析和SKS/SKKS分裂測量對青藏高原東緣地殼和上地幔各向異性進(jìn)行了研究,并且采用接收函數(shù)疊加掃描技術(shù),研究了青藏高原東緣的地殼厚度和地殼平均波速比。(1)研究區(qū)內(nèi)上地殼構(gòu)造應(yīng)力場呈現(xiàn)區(qū)域性分布。在龍門山斷裂帶,應(yīng)力方向不僅呈現(xiàn)出分段分布特征,而且在龍門山斷裂帶的前山斷裂、中央斷裂和后山斷裂也不盡相同。此外,應(yīng)力方向在龍門山斷裂帶的不連續(xù)變化可能反映了龍門山斷裂帶不是協(xié)調(diào)運動的。在龍門山以外地區(qū),應(yīng)力方向呈現(xiàn)出簡單清晰的區(qū)域性變化特征。川滇菱形塊體內(nèi)部與其東邊界的鮮水河-安寧河斷裂帶的最大壓應(yīng)力方向不同,安寧河斷裂帶以東及四川盆地以南地區(qū),最大壓應(yīng)力的方向又有所變化。最小壓應(yīng)力在整個青藏高原東緣呈現(xiàn)出比較連續(xù)的變化,但是在龍門山斷裂帶顯示出復(fù)雜的分布特征。對汶川-蘆山地震空區(qū)構(gòu)造應(yīng)力場的研究發(fā)現(xiàn),最大壓應(yīng)力在18公里上下發(fā)生明顯變化,可能反映了地殼在該深度上下為解耦變形。(2)通過接收函數(shù)集分析研究地殼各向異性,各向異性的快波方向沒有顯示出塊體分布特征,在整個青藏高原東緣呈現(xiàn)復(fù)雜的變化特征。松潘-甘孜塊體的快波方向以SE方向為主,與上地殼構(gòu)造應(yīng)力場的近W-E方向存在明顯差異。在川滇菱形塊體內(nèi),快波方向轉(zhuǎn)為基本呈SEE或SWW向。在鮮水河斷裂帶附近,快波方向基本與鮮水河斷裂帶走向平行。在四川盆地及以南地區(qū),快波方向主要為NE或NEE向。時間延遲分布在0.1-1秒范圍內(nèi),平均時間延遲為0.41秒。在龍門山斷裂帶、鮮水河斷裂帶和安寧河斷裂帶的接合處,時間延遲顯著增大。(3)采用SKS/SKKS分裂測量研究上地幔各向異性,平均時間延遲為1.2秒,顯著高于地殼0.41秒的平均時間延遲。在松潘-甘孜塊體內(nèi),快波方向主要為SSE向。而向東跨過龍門山斷裂帶進(jìn)入四川盆地,快波方向以SE向為主導(dǎo)。龍門山斷裂帶南段的快波方向呈現(xiàn)兩種特征,一種是與安寧河斷裂帶走向相平行的NNE向,另一種與四川盆地NE向的快波偏振方向相一致。四川盆地以南地區(qū),快波方向與四川盆地基本一致。鮮水河-安寧河斷裂帶的快波方向基本與斷裂帶走向平行。在川滇菱形塊體內(nèi),快波方向呈現(xiàn)非常復(fù)雜的分布,這可能反映了該塊體內(nèi)復(fù)雜的變形機(jī)制,以及塊體內(nèi)的上地幔存在不連續(xù)變形。(4)研究區(qū)內(nèi)的地殼厚度呈現(xiàn)區(qū)域性分布特征,但并不完全以區(qū)內(nèi)大型斷裂為界。地殼厚度在龍門山斷裂帶約為45公里左右,從汶川地震向南開始增厚,地殼厚度增厚至約50公里。在松潘-甘孜塊體的東北部,地殼厚度基本穩(wěn)定在48-54公里范圍內(nèi),但在松潘-甘孜塊體南部,地殼厚度為54-64公里,與川滇菱形塊體顯示出相同的分布特征。安寧河斷裂帶及四川盆地以南的地區(qū),地殼厚度基本在54公里以內(nèi),與川滇菱形塊體呈現(xiàn)明顯對比。由此可見,鮮水河斷裂帶雖然是松潘-甘孜塊體與川滇菱形塊體在地表構(gòu)造上的邊界,但并沒有構(gòu)成兩者在深部構(gòu)造上的邊界。而安寧河斷裂帶不僅是川滇菱形塊體與揚子板塊的地表構(gòu)造邊界,也是深部構(gòu)造上的邊界。(5)高波速比值主要分布在鮮水河-安寧河斷裂帶及周邊地區(qū),可能反映了這些地區(qū)具有軟弱的中下地殼。四川盆地內(nèi)部分地區(qū)波速比值可達(dá)1.8左右,特別是在龍泉斷裂一帶,可能是由于盆地內(nèi)普遍存在厚度約為6-10公里沉積層。在松潘-甘孜塊體和川滇菱形塊體內(nèi)部,絕大部分地區(qū)的地殼平均波速比在1.75左右,顯示了中等變形強度。(6)研究區(qū)內(nèi)絕大部分地區(qū)的地表GPS速度、最大壓應(yīng)力和地殼各向異性與上地幔各向異性之間均存在明顯差異,發(fā)現(xiàn)了研究區(qū)內(nèi)地殼內(nèi)以及殼幔間普遍存在的解耦運動。因此這個事實可以排除垂直連貫變形的可能性,同時為青藏高原東緣的深部變形機(jī)制為分層變形提供證據(jù)。本文認(rèn)為,青藏高原東緣內(nèi)普遍存在低速的下地殼,表現(xiàn)為下地殼滑脫層,相對高速的上地殼在滑脫層上發(fā)生遠(yuǎn)距離運移,這是青藏高原東緣的主要變形模式。
[Abstract]:The uplift of the Tibetan Plateau and expansion in the long term is one of the hot issues of earth science. Scientists have proposed many different models to explain the mechanism of deformation of the Tibetan Plateau, and in recent years the rigid crust along the large lateral strike slip faults extrusion viscous material pipeline and the lower crustal flow is the focus of debate rigid crust model fault that played a key role, while the lower crustal flow model that the lower crust from the upper crust and upper mantle decoupling. This paper collects the Longmen Mountain Fault of Sichuan seismic network with 2008-2014 years of more than 3 seismic waveform data, the moment tensor inversion 1491 earthquake focal mechanism solutions are obtained. In addition in this paper, also collected outside the study area in Longmen mountain region 695 earthquake focal mechanism solution. According to the focal mechanism solution of the fault plane parameters, this paper uses damped linear inversion The technology to obtain high resolution tectonic stress field in the study area. At the same time, this paper collected in the study area with dense broadband seismic waveform data recorded by the stations, respectively in receiver function analysis and SKS/SKKS splitting measurement on the eastern margin of the Tibetan Plateau and the crust and upper mantle anisotropy were studied, and the receiving functions. Study on the scanning technology, the eastern margin of the Tibetan Plateau the crust thickness and the average crustal velocity ratio. (1) in the study area on the crustal stress field showed the regional distribution in the Longmen Mountain Fault Zone, the stress direction not only showing sectional distribution, but also in the Longmen Mountain Fault Zone mountain front fault, central fracture and mountain fault are not the same. In addition, the stress in the direction of the Longmen Mountain Fault Zone discontinuous changes may reflect the Longmen mountain fault zone is not coordinated movement. In the area of Longmen mountain, the direction of stress Presents a simple and clear regional variations. The maximum pressure of Sichuan Yunnan block inside and east boundary of Xianshuihe ANNINGHE FAULT ZONE stress in different directions, east of the Anning River fault zone and Sichuan basin area to the south, the maximum compressive stress and the direction of change. The minimum stress shows change is continuous at the Eastern margin of the Tibetan Plateau, but in the Longmen mountain fault zone shows the distribution characteristics of the complex. The structure of Wenchuan - Lushan earthquake stress field of the gob area, the maximum compressive stress changes obviously in 18 kilometers, may reflect in the depth of crust for decoupling deformation. (2) by receiving the function set analysis of crustal anisotropy, fast wave direction anisotropy shows no block distribution, showing the complex characteristics in the eastern margin of the Qinghai Tibet Plateau. The Songpan - Ganzi block the fast direction by SE The main difference in W-E direction stress field of upper crust. In the Sichuan Yunnan rhombic block, fast direction to basic is SEE or SWW. In the vicinity of the Xianshuihe fault zone, with the fast direction parallel to the Xianshuihe fault zone. In the Sichuan basin and the south area. Fast direction is NE or NEE. The time delay distribution in 0.1- second range, the average delay time of 0.41 seconds. In the Longmen Mountain Fault Zone, joining the Xianshuihe fault zone and the Anning River fault zone, the time delay increases significantly. (3) the SKS/SKKS splitting measurement of upper mantle anisotropy, average time delay of 1.2 seconds, the average time was significantly higher than that of the crust 0.41 seconds delay. In the Songpan - Ganzi block, fast direction is mainly SSE. And to the east across the Longmen Mountain Fault Zone in Sichuan basin, with SE as the leading to the fast direction. The fast fracture zone of Longmen mountain south section The direction has two characteristics, one is NNE and ANNINGHE FAULT ZONE to parallel, consistent with another NE of the Sichuan basin to the polarization direction of fast wave. The area south of Sichuan basin, Sichuan basin and the fast direction is consistent. With the fast direction of Xianshuihe ANNINGHE FAULT and fracture in parallel with the strike. The Sichuan Yunnan rhombic block, fast direction distributes very complex, which may reflect the block complex deformation mechanism, and the block of the upper mantle is a discontinuous deformation. (4) in the study area, the crustal thickness showed the regional distribution characteristics, but not entirely in large fault in the area for the sector. The thickness of the crust in the Longmen mountain fault zone is about 45 kilometers from the Wenchuan earthquake to the South began to thicken, the crust thickness to about 50 km. In the Songpan - Ganzi block to the northeast, the crustal thickness is basically stable in the range of 48-54 km But in Songpan, the southern Ganzi block, the crustal thickness of 54-64 km, with the same distribution of Sichuan Yunnan block shows. Anning River fault zone and Sichuan basin to the south of the region, the crustal thickness basically in 54 kilometers, obviously compared with the Sichuan Yunnan block. Thus, fresh river fault zone is the boundary of Songpan Ganzi block and the Sichuan Yunnan rhombic block on the surface of structure, but does not constitute both in the deep structure of the boundary. The Anninghe fault zone is not only the Sichuan Yunnan rhombic block body surface tectonic boundary and the Yangtze plate, and the deep structure of the boundary Gao Bo. (5) ratio of the main distribution zone and surrounding areas in the Xianshuihe ANNINGHE FAULT, may reflect these areas with a weak lower crust in the Sichuan basin. Parts of velocity ratio can reach about 1.8, especially in the vicinity of the Longquan fault, may be due to the basin In common about 6-10 kilometers thick sedimentary layer. In Songpan Ganzi block and the Sichuan Yunnan rhombic block, the vast majority of crustal average wave velocity ratio at around 1.75, showing moderate deformation strength. (6) in the study area in most regions of the surface of GPS speed, the maximum compressive stress was significant the difference between the force and the crustal anisotropy and mantle anisotropy, found the crust in the study area and prevailing between crust and mantle decoupling motion. Therefore this fact can exclude the possibility of vertically coherent deformation, and deep into the eastern margin of the Tibetan Plateau deformation mechanism so as to provide evidence for the layered deformation. This paper argues that the widespread presence of crust of the eastern margin of the Tibetan Plateau, showed lower crustal detachment layer, the upper crust in the relatively high speed on the long-distance transport detachment layer, which is the main deformation mode of the eastern margin of the Tibetan Plateau.

【學(xué)位授予單位】：成都理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：P315.2

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