本文選題：汶川地震　切入點(diǎn)：震前形變特征　出處：《中國地震局地震預(yù)測(cè)研究所》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：汶川震前在震中區(qū)及其附近存在多種形變資料,比如GPS、地傾斜、跨斷層水準(zhǔn)、重力等。根據(jù)汶川震前的形變觀測(cè)資料分析研究表明,和遠(yuǎn)震區(qū)變形相比,近震區(qū)變形趨勢(shì)減弱,而且在龍門山斷層附近呈現(xiàn)變異帶;在汶川震前3 8年時(shí)間段的變形以及重力變化相對(duì)來說比較顯著,而在震前1-3年的時(shí)間段內(nèi)變化逐漸趨于平緩。呈現(xiàn)“越靠近震中變形越不顯著;越靠近震前,變形越平緩”的這一特點(diǎn)。根據(jù)形變場(chǎng)、重力場(chǎng)以及密度場(chǎng)的資料及理論分析,表明三者存在較為緊密的關(guān)系。因?yàn)榈貧の镔|(zhì)密度的變化可以更加直觀地反映汶川地震“孕育”、發(fā)生和發(fā)展的深層動(dòng)力過程。為揭示震前變形現(xiàn)象,本文開展了利用重力反演地殼密度的研究。利用龍門山區(qū)域重力網(wǎng)提供的1996-2007年的13期的流動(dòng)重力資料,借助重力位場(chǎng)三維反演技術(shù),對(duì)近震區(qū)地下不同深度的物質(zhì)密度的動(dòng)態(tài)變化過程進(jìn)行了反演。結(jié)果表明:空間分布上,整個(gè)地區(qū)的密度變化分布不均勻,個(gè)別區(qū)域密度變化顯著,尤其在龍門山斷裂帶及其附近,布格重力異常圖、地殼等厚圖和密度變化圖均表現(xiàn)為梯度陡變帶,是物質(zhì)變遷和構(gòu)造變形差異運(yùn)動(dòng)強(qiáng)烈的地帶,說明地表構(gòu)造和深部構(gòu)造都位于變異帶上;在時(shí)間序列上,不同時(shí)間段內(nèi)地殼介質(zhì)密度的變化速率呈現(xiàn)橫向不均勻性和階段性,龍門山地區(qū)在震前10年密度變化就有增大的趨勢(shì),震前8-5年間變化最為劇烈,而臨震前的變化則比較平緩;在垂向上,一定深度范圍內(nèi),隨深度的增加密度變化的程度越來越顯著,說明深部的地殼活動(dòng)比淺部活動(dòng)大的多。此外,臨震前短期內(nèi),重力變化、密度場(chǎng)變化空間分布上均呈現(xiàn)有序性和相對(duì)集中性,與形變場(chǎng)震前減熵的現(xiàn)象是吻合的�？傊�,密度場(chǎng)動(dòng)態(tài)變化的趨勢(shì)和重力場(chǎng)以及形變場(chǎng)的變化趨勢(shì)比較一致。密度動(dòng)態(tài)變化場(chǎng)的結(jié)果為選取適合汶川地震的孕育模型以及動(dòng)力演化過程提供支持和佐證:為解釋震前淺部小變形和深部密度顯著變化的矛盾現(xiàn)象,提出汶川地震的“孕育”、發(fā)生和發(fā)展是上地殼和下地殼不處于同一個(gè)力源匹配系統(tǒng),導(dǎo)致上、下地殼運(yùn)動(dòng)不統(tǒng)一的結(jié)果;結(jié)合密度變化的特征,選取出適合汶川地震的組合—硬化孕育模型,對(duì)震前短期以及近震源區(qū)的無顯著變形這一現(xiàn)象進(jìn)行了一定的揭示,加深了對(duì)震前形變前兆變化的機(jī)理的認(rèn)識(shí)。本文的研究思路是通過地表形變和深部地球物理資料(地下密度)建立近震源區(qū)的孕震演化過程與動(dòng)力學(xué)過程,用深部的地球物理資料為孕震模型提供支持,進(jìn)而探討震前小形變的機(jī)理。由于地下深部的變形涉及多方面的未明確因素,而且深部變形難以被精細(xì)探測(cè),故本文的研究未能對(duì)地形變機(jī)理做出完善的解釋,但為深部的密度變化及地殼形變研究提出了一種可行的研究方法。
[Abstract]:Before the Wenchuan earthquake, there are a variety of deformation data in and around the epicentre, such as GPS, ground tilt, cross-fault leveling, gravity, etc. According to the analysis of deformation observation data before Wenchuan earthquake, it is shown that the deformation trend in the near earthquake area is weaker than that in the far earthquake area. In addition, there is a variation zone near the Longmenshan fault, and the deformation and gravity changes are relatively significant in the period of 3 years before the Wenchuan earthquake. However, in the period of 1-3 years before the earthquake, the variation tends to be more and more gentle. It presents the characteristic of "the closer the epicentral deformation is, the more gentle the deformation is before the earthquake." according to the data and theoretical analysis of the deformation field, gravity field and density field, The results show that there is a close relationship among them, because the change of crustal material density can reflect more intuitively the deep dynamic process of Wenchuan earthquake's "gestation", occurrence and development, in order to reveal the phenomenon of deformation before the earthquake. In this paper, the study of inversion of crustal density by gravity is carried out. Using the 13 periods of fluid gravity data from 1996 to 2007 provided by the Longmen Mountain Regional Gravity Network, the three-dimensional inversion technique of gravity potential field is used. In this paper, the dynamic change process of mass density at different depths in the near seismic area is inversed. The results show that the density variation of the whole area is not uniform in spatial distribution, and the density change in individual regions is remarkable. Especially in the Longmenshan fault zone and its vicinity, the Bouguer gravity anomaly map, crustal isothickness map and density change map all show gradient steepness zone, which are the areas with strong difference between material change and tectonic deformation. It shows that both the surface structure and the deep structure are located in the variation zone, and in the time series, the change rate of the density of the crustal media in different time periods presents transversal inhomogeneity and phase. The density change in Longmen Mountain area has an increasing trend in 10 years before the earthquake, and the change is the most intense in the 8-5 years before the earthquake, but the change before the earthquake is relatively gentle, and in the vertical direction, within a certain depth, The change of density with depth is more and more obvious, which indicates that the crustal activity in depth is larger than that in shallow. In addition, the spatial distribution of gravity change and density field change is orderly and relatively concentrated in the short term before earthquake. It is consistent with the phenomenon of entropy reduction before the deformation field. In short, The dynamic change trend of density field is consistent with that of gravity field and deformation field. The result of density dynamic change field provides support and evidence for selecting the breeding model and dynamic evolution process suitable for Wenchuan earthquake. To explain the contradiction between the small deformation in shallow part before the earthquake and the significant change in deep density. It is proposed that the occurrence and development of Wenchuan earthquake is caused by the fact that the upper crust and the lower crust are not in the same force source matching system, which leads to the disunity of upper and lower crustal movements, and combines the characteristics of density variation. The combined hardening inoculation model suitable for Wenchuan earthquake is selected and the phenomenon of no significant deformation in the short term before the earthquake and near the focal area is revealed. The research idea of this paper is to establish the seismogenic evolution process and dynamic process of near-focal area through surface deformation and deep geophysical data (underground density). The deep geophysical data are used to support the seismogenic model and the mechanism of the small deformation before the earthquake is discussed. Because the deformation in the underground depth involves many undefined factors, and the deep deformation is difficult to be accurately detected, Therefore, the research in this paper can not make a perfect explanation for the mechanism of topographic deformation, but it provides a feasible method for the study of the density variation and crustal deformation in the deep part.
【學(xué)位授予單位】：中國地震局地震預(yù)測(cè)研究所
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P315.72

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 牛安福;張凌空;閆偉;吉平;;汶川地震近震源區(qū)地形變短期前兆現(xiàn)象的解析[J];地震;2012年02期

2 邢樂林;李輝;何志堂;董正瑤;談洪波;;成都基準(zhǔn)臺(tái)絕對(duì)重力復(fù)測(cè)結(jié)果分析[J];大地測(cè)量與地球動(dòng)力學(xué);2008年06期

3 王衛(wèi)民;趙連鋒;李娟;姚振興;;四川汶川8.0級(jí)地震震源過程[J];地球物理學(xué)報(bào);2008年05期

4 聞學(xué)澤;張培震;杜方;龍鋒;;2008年汶川8.0級(jí)地震發(fā)生的歷史與現(xiàn)今地震活動(dòng)背景[J];地球物理學(xué)報(bào);2009年02期

5 杜義;謝富仁;張效亮;荊振杰;;汶川M_s8.0級(jí)地震斷層滑動(dòng)機(jī)制研究[J];地球物理學(xué)報(bào);2009年02期

6 江在森;方穎;武艷強(qiáng);王敏;杜方;平建軍;;汶川8.0級(jí)地震前區(qū)域地殼運(yùn)動(dòng)與變形動(dòng)態(tài)過程[J];地球物理學(xué)報(bào);2009年02期

7 張季生;高銳;曾令森;李秋生;管燁;賀日政;王海燕;盧占武;;龍門山及鄰區(qū)重、磁異常特征及與地震關(guān)系的研究[J];地球物理學(xué)報(bào);2009年02期

8 王武星;石耀霖;顧國華;張晶;陳石;;GRACE衛(wèi)星觀測(cè)到的與汶川M_s 8.0地震有關(guān)的重力變化[J];地球物理學(xué)報(bào);2010年08期

9 姚琪;徐錫偉;邢會(huì)林;張微;高翔;;青藏高原東緣變形機(jī)制的討論:來自數(shù)值模擬結(jié)果的限定[J];地球物理學(xué)報(bào);2012年03期

10 安玉林,陳玉東,黃金明;重磁勘探正反演理論方法研究的新進(jìn)展[J];地學(xué)前緣;2003年01期

，

本文編號(hào)：1612199