發(fā)布時(shí)間：2018-09-13 09:52

【摘要】：地應(yīng)力是影響地震發(fā)生的重要因素之一。大地震前后地應(yīng)力狀態(tài)的研究對(duì)于探索地震的孕育和發(fā)生機(jī)制具有重要的意義和作用。本文首先采用中國(guó)大陸三維球殼有限元蠕變模型,以實(shí)際觀測(cè)成果為約束,獲得中國(guó)大陸現(xiàn)今背景應(yīng)力場(chǎng)。然后,通過(guò)給定發(fā)震單元的臨界應(yīng)力值,模擬5.12汶川大地震斷層脆性失效引起的地應(yīng)力變化。模擬結(jié)果與前人研究得到的汶川地震后的應(yīng)力場(chǎng)特征較為吻合。通過(guò)淺部實(shí)測(cè)的水平最大主應(yīng)力大小、方位和深部震源機(jī)制所反映的應(yīng)力類(lèi)型作為模型的目標(biāo)約束條件,確定了較為合理的邊界條件,模擬得到了中國(guó)大陸現(xiàn)今背景應(yīng)力場(chǎng),其特征為：(1)受印度塊體、歐亞塊體、菲律賓塊體和太平洋塊體的相對(duì)運(yùn)動(dòng)的作用,中國(guó)大陸地殼淺部水平最大主應(yīng)力方位由南北方位繞青藏高原東構(gòu)造結(jié)順時(shí)針旋轉(zhuǎn),水平最大主應(yīng)力方位在上地殼30km范圍內(nèi)具有一致性。(2)斷裂帶附近區(qū)域的最大水平主應(yīng)力方位變化具有不連續(xù)性,最大水平主應(yīng)力大小受到斷層性質(zhì)影響。(3)深度2000 m的水平最大主應(yīng)力量值在10 MPa-80 MPa之間,青藏塊體、西域塊體最高,東南塊體最低,其它塊體中等。(4)深度2000 m處,龍門(mén)山斷裂帶附近區(qū)域的水平最大主應(yīng)力在南部方位為SE-E,北部方位為NE-E。(5)龍門(mén)山斷裂帶在豎直剖面上的差應(yīng)力從上地殼到中地殼逐漸增大。深度4000 m以下到中地殼的差應(yīng)力比下地殼的大。由此推斷斷層淺部差應(yīng)力較大,可能容易造成斷層破壞。在中國(guó)大陸現(xiàn)今背景應(yīng)力場(chǎng)下,以5.12汶川地震為例,分析斷層脆性失效引起的應(yīng)力場(chǎng)變化。建立破裂面上局部坐標(biāo)系和斷層面上最大剪切失效準(zhǔn)則,降低剪切模量模擬研究地震破裂面上脆性斷裂。汶川地震發(fā)生后,地殼應(yīng)力場(chǎng)顯示：(1)龍門(mén)山中央斷裂帶中段和北段淺部的水平最大主應(yīng)力有較大的下降,斷裂帶周?chē)鷳?yīng)力受到地震影響較大,下降量值隨著距斷裂帶的距離增加而減小。差應(yīng)力下降較為明顯,下降大小隨著距斷裂帶距離的增加而減小。最大水平主應(yīng)力計(jì)算變化量值與淺表應(yīng)力震后實(shí)測(cè)量變化的量值相當(dāng)。(2)龍門(mén)山南段應(yīng)力在整個(gè)斷裂帶中依然高于其它地區(qū),斷裂帶南段依然處于高應(yīng)力積累之中。(3)斷裂帶上水平最大主應(yīng)力的總體方位較一致,在震中位置深度2000m處水平最大主應(yīng)力方位290°。與汶川地震前的計(jì)算結(jié)果對(duì)比,地震發(fā)生前的水平最大主應(yīng)力為2800,說(shuō)明地震前后水平最大主應(yīng)力發(fā)生了順時(shí)針旋轉(zhuǎn),旋轉(zhuǎn)角度10°左右。由于受到此模型誤差影響,此結(jié)果僅能作為應(yīng)力變化的參考值,精度還有待提高。本模型可作為解釋強(qiáng)震遠(yuǎn)距觸發(fā)、遷移的基礎(chǔ)。對(duì)于斷層摩擦滑動(dòng)失效和壓碎破壞等斷層失效機(jī)制的研究以及模型精度改進(jìn)有待進(jìn)一步工作。
[Abstract]:Ground stress is one of the important factors that affect the occurrence of earthquake. The study of in-situ stress state before and after a large earthquake is of great significance and function in exploring the mechanism of earthquake preparation and occurrence. In this paper, the 3-D spherical shell finite element creep model is used to obtain the present background stress field in the mainland of China. Then, the variation of in-situ stress caused by brittle failure of the 5.12 Wenchuan earthquake fault is simulated by the critical stress value of the seismogenic unit. The simulation results are in good agreement with the characteristics of the stress field after Wenchuan earthquake. By using the maximum horizontal principal stress, azimuth and the stress type reflected by the deep focal mechanism as the target constraint conditions of the model, the reasonable boundary conditions are determined, and the present background stress field in the mainland of China is simulated. Its characteristics are as follows: (1) due to the relative movement of the Indian block, Eurasian block, Philippine block and Pacific block, the maximum horizontal principal stress orientation of the shallow crust of the Chinese mainland rotates clockwise around the eastern tectonic junction of the Qinghai-Xizang Plateau from the position of the south to the north. The azimuth of horizontal maximum principal stress is consistent in the 30km range of upper crust. (2) the variation of maximum horizontal principal stress azimuth in the area near the fault zone is discontinuous. The maximum horizontal principal stress is affected by the fault properties. (3) the maximum horizontal principal stress value of 2000 m depth is between 10 MPa-80 MPa, the Qinghai-Tibet block, the western region block is the highest, the southeast block is the lowest, and the other blocks are medium. (4) the depth is 2000 m. The maximum horizontal principal stress in the area near the Longmenshan fault zone is in the southern direction: the northern direction of SE-E, is NE-E. (5) the differential stress in the vertical section of the Longmenshan fault zone increases gradually from the upper crust to the middle crust. The differential stress from the depth below 4000 m to the middle crust is greater than that from the lower crust. It can be concluded that the shallow differential stress of the fault is large, which may easily lead to the failure of the fault. Taking the 5.12 Wenchuan earthquake as an example, the variation of stress field caused by fault brittleness failure is analyzed under the background stress field of mainland China. The local coordinate system on the fracture surface and the maximum shear failure criterion on the fault plane are established, and the brittle fracture on the seismic fracture surface is simulated by reducing the shear modulus. After the Wenchuan earthquake occurred, the crustal stress field showed: (1) the horizontal maximum principal stress in the middle and north segment of the central fault zone of Longmen Mountain decreased greatly, and the stress around the fault zone was greatly affected by the earthquake. The drop value decreases with the increase of the distance from the fault zone. The difference stress decreases obviously and decreases with the increase of the distance from the fault zone. The calculated variation value of maximum horizontal principal stress is equivalent to that measured after shallow surface stress earthquake. (2) the stress in the southern section of Longmen Mountain is still higher than that in other regions in the whole fault zone. The southern segment of the fault zone is still in the process of high stress accumulation. (3) the overall orientation of the maximum horizontal principal stress in the fault zone is consistent, and the maximum horizontal principal stress direction is 290 擄at the depth of 2000m in the epicenter. Compared with the calculated results before the Wenchuan earthquake, the maximum horizontal principal stress before the earthquake is 2800, which indicates that the maximum horizontal principal stress rotates clockwise before and after the earthquake, and the rotation angle is about 10 擄. Because of the influence of the model error, the result can only be used as the reference value of the stress change, and the accuracy needs to be improved. This model can be used as the basis for explaining the remote triggering and migration of strong earthquakes. The research of fault failure mechanism such as fault friction sliding failure and crushing failure and the improvement of model precision need further work.
【學(xué)位授予單位】：中國(guó)地震局地殼應(yīng)力研究所
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：P315.727

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 張國(guó)民,李獻(xiàn)智,耿魯明;印度板塊北邊界地震活動(dòng)和中國(guó)大陸地震[J];地震;1994年03期

2 張東寧,許忠淮;中國(guó)大陸地殼應(yīng)變能密度年變化率圖像與強(qiáng)震活動(dòng)關(guān)系的初步探討[J];地震;1999年01期

3 李昶,臧紹先;巖石層流變學(xué)的研究現(xiàn)狀及存在問(wèn)題[J];地球物理學(xué)進(jìn)展;2001年02期

4 黃璽瑛,魏東平;世界應(yīng)力圖2000版(WSM2000)介紹及使用說(shuō)明[J];地球物理學(xué)進(jìn)展;2003年02期

5 謝富仁;陳群策;崔效鋒;李宏;楊樹(shù)新;郭啟良;陳連旺;許忠淮;張彥山;竇淑芹;趙建濤;張周術(shù);劉長(zhǎng)義;王剛軍;;中國(guó)大陸地殼應(yīng)力環(huán)境基礎(chǔ)數(shù)據(jù)庫(kù)[J];地球物理學(xué)進(jìn)展;2007年01期

6 闞榮舉,張四昌,晏鳳桐,俞林勝;我國(guó)西南地區(qū)現(xiàn)代構(gòu)造應(yīng)力場(chǎng)與現(xiàn)代構(gòu)造活動(dòng)特征的探討[J];地球物理學(xué)報(bào);1977年02期

7 李方全,王連捷;華北地區(qū)地應(yīng)力測(cè)量[J];地球物理學(xué)報(bào);1979年01期

8 謝富仁,崔效鋒,趙建濤,陳群策,李宏;中國(guó)大陸及鄰區(qū)現(xiàn)代構(gòu)造應(yīng)力場(chǎng)分區(qū)[J];地球物理學(xué)報(bào);2004年04期

9 鄭勇;傅容珊;熊熊;;中國(guó)大陸及周邊地區(qū)現(xiàn)代巖石圈演化動(dòng)力學(xué)模擬[J];地球物理學(xué)報(bào);2006年02期

10 陸遠(yuǎn)忠;葉金鐸;蔣淳;劉杰;;中國(guó)強(qiáng)震前兆地震活動(dòng)圖像機(jī)理的三維數(shù)值模擬研究[J];地球物理學(xué)報(bào);2007年02期

相關(guān)博士學(xué)位論文 前1條

1 楊樹(shù)新;中國(guó)陸域地殼應(yīng)力場(chǎng)分布特征研究[D];北京交通大學(xué);2013年

相關(guān)碩士學(xué)位論文 前1條

1 張曦;龍門(mén)山地區(qū)地震前后地應(yīng)力特征及突變規(guī)律[D];成都理工大學(xué);2014年

，

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