本文選題：川滇地區(qū)　切入點：地殼變形　出處：《中國地質(zhì)大學(xué)(北京)》2016年博士論文

【摘要】：為探索川滇地區(qū)地殼變形的動力學(xué)成因及強震間相互作用機理,論文基于川滇地區(qū)較為精細(xì)的三維粘彈性有限元模型,通過開展多組數(shù)值模擬實驗,探討下地殼流、介質(zhì)流變性差異、活動斷裂等對地殼變形的影響,獲得較為理想的川滇地區(qū)動力學(xué)模型。在此基礎(chǔ)上,考慮震間、同震及震后效應(yīng)的影響,分析1970年通海M7.7級地震以來川滇地區(qū)15次強震之間的相互作用過程及強震發(fā)生造成區(qū)域主要活動斷裂的應(yīng)力場演化。研究結(jié)果表明,下地殼流在川滇地區(qū)的地殼變形中起重要作用,當(dāng)下地殼流動速度比上地殼快約10~11mm/a時,速度場大小、方向的模擬值與GPS實際觀測值均吻合較好。華南塊體中下地殼粘滯系數(shù)增加時,介質(zhì)的流變性差異造成相鄰塊體運動學(xué)特征的變化,使得模擬值與觀測值吻合程度更高�；顒訑嗔训拇嬖谖沾ǖ岬貐^(qū)地殼的運動,從而造成塊體間相對差異性運動。模擬給出的鮮水河斷裂左旋滑動速率最大達(dá)9.55mm/a,而安寧河、則木河、小江斷裂左旋滑動速率相對較小,在3.1~9.4mm/a間變化�；诶硐雱恿W(xué)模型的應(yīng)力場模擬結(jié)果表明,川滇地區(qū)15km深處最大主應(yīng)力場呈現(xiàn)明顯的分區(qū)特征,從北部巴顏喀拉塊體的近東西向逐步轉(zhuǎn)變到華南塊體的南東向、滇西塊體的北東向及滇南塊體的輻射發(fā)散狀分布。若將川滇地區(qū)的龍陵雙震及瀾滄-耿馬地震分別處理為一次地震事件,對于發(fā)生在自1970年通海M7.7級地震以來的13次強震,在視摩擦系數(shù)'?=0.4或0.6時,6次強震發(fā)生在先前地震發(fā)生所引起的應(yīng)力增加區(qū)內(nèi),2次發(fā)生在應(yīng)力影區(qū)內(nèi),4次地震基本未受先前地震影響,處于應(yīng)力增加區(qū)內(nèi)的地震占50%。同時,在兩次松潘M7.2級強震之間存在明顯的應(yīng)力觸發(fā)作用。就同震作用分析表明,在視摩擦系數(shù)'?=0.4時,1976年8月16日松潘M7.2級地震造成8月23日M7.2級地震震中滑動方向產(chǎn)生的庫侖破裂應(yīng)力達(dá)0.217MPa,明顯高于地震觸發(fā)的閾值0.01MPa。在系列強震發(fā)生之后,應(yīng)力增加較為明顯的斷裂有:龍陵-瀾滄斷裂北段、孟連-瀾滄斷裂北東段、鮮水河斷裂北西段斷層交匯區(qū)、虎牙斷裂中段及龍門山斷裂中南段,最大增加量達(dá)1.5MPa。
[Abstract]:In order to explore the dynamic causes of crustal deformation and the interaction mechanism between strong earthquakes in Sichuan-Yunnan area, the paper discusses the lower crustal flow based on three dimensional viscoelastic finite element model of Sichuan-Yunnan region, and carries out a number of numerical simulation experiments.An ideal dynamic model of Sichuan-Yunnan region is obtained by the difference of rheological properties of medium and the influence of active faults on crustal deformation.On this basis, the interaction process between 15 strong earthquakes in Sichuan-Yunnan region since the 1970 Tonghai M 7.7 earthquake and the evolution of the stress field of the main active faults caused by the strong earthquakes are analyzed taking into account the effects of interseismic, co-seismic and post-earthquake effects.The results show that the lower crustal flow plays an important role in crustal deformation in Sichuan-Yunnan area. When the velocity of crustal flow is about 10~11mm/a faster than that of the upper crust, the simulated values of velocity field and direction are in good agreement with the observed values of GPS.When the viscosity coefficient of the lower crust increases in the middle and lower crust of the South China block, the difference in rheological properties of the media results in the change of the kinematic characteristics of the adjacent blocks, which makes the simulated value more consistent with the observed value.The existence of active faults absorbs crustal movement in Sichuan-Yunnan area, resulting in relatively differential movement among blocks.The maximum left lateral slip rate of Xianshuihe fault is 9.55 mm / a, while that of Anning River, Nemu River and Xiaojiang fault is relatively small, and the variation of the rate between 3.1~9.4mm/a is relatively small.The simulation results of stress field based on ideal dynamic model show that the maximum principal stress field in the deep 15km of Sichuan-Yunnan region shows obvious zoning characteristics, and the maximum principal stress field changes gradually from the near east-west direction of the northern Bayan Kara block to the south-east direction of the southern China block.The north-east direction of the western Yunnan block and the radiative divergence of the southern Yunnan block.If the Longling double earthquake and Lancang-Gengma earthquake in Sichuan-Yunnan region are treated as one earthquake event, 13 strong earthquakes occurred since the M 7.7 earthquake in the Tonghai area in 1970.When the apparent friction coefficient is 0. 4 or 0. 6, 6 strong earthquakes occur in the stress increase zone caused by the previous earthquake. Two or four earthquakes occur in the stress shadow area, and 50 earthquakes are in the stress increasing area.At the same time, there is obvious stress triggering effect between two strong earthquakes with M 7.2 in Songpan.The analysis of coseismicity shows that the Coulomb rupture stress in the epicentral slip direction of the M 7.2 earthquake on August 23, 1976 caused by the apparent friction coefficient is 0.4, which is obviously higher than the threshold value of 0.01MPa triggered by the earthquake.After the occurrence of a series of strong earthquakes, the faults with obvious stress increase are: the northern segment of Longling-Lancang fault, the east segment of Menglian-Lancang fault, the fault intersection area of the north west section of Xianshuihe fault, the middle segment of Huya fault and the central and southern segment of Longmenshan fault.The maximum increment is 1.5 MPA.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：P315.2

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