本文關(guān)鍵詞：GPS觀測(cè)研究現(xiàn)今青藏高原地殼形變機(jī)制——來自阿爾金斷裂三維運(yùn)動(dòng)場(chǎng)及高原地殼減薄的證據(jù)　出處：《國際地震動(dòng)態(tài)》2017年09期 　論文類型：期刊論文

  更多相關(guān)文章： 青藏高原 阿爾金斷裂中段 連續(xù)GPS觀測(cè) 三維彈性后向滑移塊體模型 地殼減薄

【摘要】：自50~55 Ma以來,印度次大陸向北與歐亞大陸碰撞后形成喜馬拉雅—青藏高原造山帶,碰撞導(dǎo)致地殼增厚致使高原大幅隆升,改變了亞洲大陸巖石圈的構(gòu)造格局,也對(duì)東亞地區(qū)的氣候和環(huán)境產(chǎn)生了巨大影響。阿爾金斷裂作為青藏高原北緣的主控邊界斷裂,其運(yùn)動(dòng)學(xué)性質(zhì)在20世紀(jì)70年代備受關(guān)注,不同量級(jí)的滑動(dòng)速率引出了塊體運(yùn)動(dòng)與東向逃逸和連續(xù)變形與地殼增厚兩種端元模型。約10~15 Ma以來,在青藏高原南部與北部出現(xiàn)地塹與裂谷,為高原東西向拉張運(yùn)動(dòng)提供了證據(jù),表明青藏高原開始經(jīng)歷地殼減薄過程。青藏高原形成以來形變場(chǎng)經(jīng)歷怎樣變化,長時(shí)間尺度的地質(zhì)學(xué)構(gòu)造過程與現(xiàn)今GPS觀測(cè)是否能夠統(tǒng)一?10~15 Ma以來青藏高原地殼減薄過程造成高原高程怎樣的變化?青藏高原北緣,尤其是跨阿爾金斷裂具有怎樣的現(xiàn)今三維地殼變形場(chǎng),地殼應(yīng)變是如何在北阿爾金斷裂、祁漫塔格斷裂和阿爾金斷裂之間分配的?青藏高原北緣與塔里木盆地具有怎樣的力學(xué)性質(zhì),對(duì)跨阿爾金斷裂構(gòu)造形變場(chǎng)造成怎樣的影響?最后,GPS觀測(cè)得到的現(xiàn)今地表形變場(chǎng)能夠?qū)η嗖馗咴巫兡Ｊ降臓幷撟鞒龊畏N解答?上述科學(xué)問題的解答,對(duì)于研究青藏高原隆升與變形過程具有十分重要的意義。本研究分為兩部分。第一部分是青藏高原北緣三維震間運(yùn)動(dòng)場(chǎng)的觀測(cè)與研究。在青藏高原北緣跨阿爾金斷裂中段自建9個(gè)GPS連續(xù)臺(tái)站并開展觀測(cè),根據(jù)區(qū)域研究特點(diǎn)設(shè)計(jì)無人值守的觀測(cè)臺(tái)站,具有低成本投入、高質(zhì)量觀測(cè)的特點(diǎn)。上述連續(xù)GPS臺(tái)站的建立填補(bǔ)了青藏高原北緣,尤其是在阿爾金無人區(qū)地殼形變觀測(cè)研究的空白,積累了寶貴的連續(xù)GPS數(shù)據(jù);截止2015年7月,共有4年的連續(xù)GPS觀測(cè)。數(shù)據(jù)分析結(jié)果證明,設(shè)計(jì)建站方法行之有效,GPS臺(tái)站穩(wěn)定、觀測(cè)數(shù)據(jù)質(zhì)量穩(wěn)定、數(shù)據(jù)連續(xù)性穩(wěn)定。結(jié)合使用中國大陸構(gòu)造環(huán)境監(jiān)測(cè)網(wǎng)絡(luò)在研究區(qū)及鄰域GPS連續(xù)臺(tái)站數(shù)據(jù)作位置時(shí)間序列與速度場(chǎng)解算,獲得青藏高原北緣地區(qū)跨阿爾金斷裂中段現(xiàn)今三維形變場(chǎng)。使用三維線彈性后向滑移(backslip)塊體運(yùn)動(dòng)模型,反演塔里木塊體、北阿爾金塊體、柴達(dá)木塊體和祁漫塔格塊體的三維塊體運(yùn)動(dòng)。結(jié)果表明,北阿爾金山相對(duì)于塔里木盆地有(1.32±0.2)mm/a的抬升速率,相對(duì)于柴達(dá)木盆地具有(0.73±0.3)mm/a的抬升速率,可解釋為北阿爾金塊體存在顯著的造山過程;阿爾金斷裂有(8.21±0.60)mm/a的左旋走滑速率、(0.66±0.60)mm/a的縮短速率;祁漫塔格斷裂有(0.53±0.60)mm/a的左旋走滑速率、(1.53±0.60)mm/a的縮短速率;北阿爾金斷裂有(0.87±0.60)mm/a的左旋速率、(0.69±0.60)mm/a的縮短速率。同時(shí),阿爾金斷裂中、西兩段滑動(dòng)速率基本一致,約為8.0~10.0mm/a。定量研究結(jié)果支持連續(xù)形變與地殼增厚模型,表明相對(duì)塔里木塊體,青藏高原北緣地區(qū)正在抬升、增厚,以北阿爾金山地區(qū)最為明顯,抬升速率約達(dá)1.3mm/a�？缜嗖馗咴本壍陌柦饠嗔选⒈卑柦饠嗔押推盥駭嗔呀�200km的寬泛變形帶內(nèi),南北向地殼縮短并不明顯,縮短量僅約為2.9mm,且近一半縮短量發(fā)生在祁漫塔格山南側(cè)。GPS觀測(cè)阿爾金斷裂車爾臣河段(~86°E)剖面表明,斷裂兩側(cè)存在非對(duì)稱變形特征。本文采用非對(duì)稱變形模型反演GPS速度剖面數(shù)據(jù),獲得斷裂兩側(cè)塔里木盆地和青藏高原北部的地殼介質(zhì)剪切模量差異。結(jié)果顯示,塔里木盆地地殼介質(zhì)剪切模量約為青藏高原北部剪切模量1.53倍,相應(yīng)S波波速比值為1.24,與Yang等人得到的地殼和上地幔三維VSV模型結(jié)果一致。地震學(xué)研究結(jié)果認(rèn)為,青藏高原北部與東部地區(qū)在中地殼存在低速層,局部區(qū)域可能發(fā)生部分熔融;Hacker等進(jìn)一步確認(rèn)羌塘地塊中地殼到深部地殼存在熔融現(xiàn)象。本文的研究運(yùn)用了與地震學(xué)完全不同的資料,通過大地測(cè)量方法推導(dǎo)青藏高原北部與塔里木盆地的地殼介質(zhì)力學(xué)性質(zhì)差異,得到與地震學(xué)研究得到的S波波速比及其構(gòu)造物理學(xué)解釋相當(dāng)一致的結(jié)果。成果為青藏高原力學(xué)演化模型提供新的約束。本論文第二部分內(nèi)容是使用覆蓋青藏高原及周邊的GPS速度場(chǎng),計(jì)算青藏高原內(nèi)部應(yīng)變率場(chǎng)。GPS觀測(cè)速度場(chǎng)不僅顯示了南東東-北西西向的地殼拉張過程,也揭示了青藏高原內(nèi)部更加重要的地殼減薄過程。結(jié)果顯示,青藏高原北部和南部的垂向應(yīng)變率(減薄應(yīng)變率)分別為(8.9±0.8)nanostrain/a和(7.4±1.2)nanostrain/a,青藏高原西南部的垂向應(yīng)變率為(12.0±3.2)nanostrain/a,表明青藏高原內(nèi)部大尺度范圍應(yīng)變率測(cè)量結(jié)果的一致性。并且青藏高原內(nèi)部的拉張應(yīng)變率觀測(cè)也相當(dāng)一致,青藏高原北部,沿著N114±1°E主應(yīng)變方向的拉張應(yīng)變率為(21.9±0.4)nanostrain/a;高原南部沿著N93±1°E主應(yīng)變方向的拉張應(yīng)變率為(16.9±0.2)nanostrain/a;高原西南部沿著N74±3°E主應(yīng)變方向的拉張應(yīng)變率為(22.2±1.8)nanostrain/a。如果地殼減薄開始于10~15 Ma,并且現(xiàn)今觀測(cè)得到應(yīng)變率適用于整個(gè)時(shí)間跨度,那么地殼累積減薄5.5~8.5km。應(yīng)用Airy地殼均衡理論,青藏高原的平均高程將下降~1km。青藏高原北部、南部和西南部相似的垂向應(yīng)變速率也表明,在3個(gè)區(qū)域的地殼拉張、正斷裂運(yùn)動(dòng)和地殼減薄過程由相同的物理機(jī)制所支配。綜合上述兩部分研究成果,發(fā)現(xiàn)青藏高原現(xiàn)今垂向運(yùn)動(dòng)在高原內(nèi)部和邊緣地區(qū)存在很大差別。高原內(nèi)部地區(qū)正在經(jīng)歷地殼減薄,而高原邊緣地區(qū)正在經(jīng)歷不同程度的增厚與隆升。青藏高原北緣地區(qū)的垂向應(yīng)變率約5~20nanostrain/a,如果考慮重力均衡作用,對(duì)應(yīng)的垂向隆升速率在0.04~0.14mm/a左右。但是,對(duì)于局部地區(qū)如北阿爾金塊體,其底部受到塔里木盆地南緣下插撓曲板塊的支持,在沒有重力均衡情況下,垂向隆升速率可能達(dá)到1mm/a。喜馬拉雅地區(qū)呈現(xiàn)不同水平的垂向形變,垂向應(yīng)變強(qiáng)烈(約10~80nanostrain/a),山脈底部受到印度下插板片的支持,無法通過重力均衡假定由垂向應(yīng)變率估計(jì)隆升速率。但由GPS與水準(zhǔn)數(shù)據(jù)約束的俯沖板片模型推測(cè)山脈隆升速率達(dá)到約7mm/a。而對(duì)于祁連山地區(qū),GPS應(yīng)變率推測(cè)得到垂向應(yīng)變率約20~40nanostrain/a,應(yīng)用地殼均衡理論,平均隆升速率為0.15~0.3mm/a;而由于逆沖推覆構(gòu)造與褶皺變形帶的存在,中下地殼有可能仍存在彈性變形,不能實(shí)現(xiàn)完全重力均衡,實(shí)際隆升速率有可能高于這一估計(jì)。本文研究給出青藏高原不同地區(qū)三維形變場(chǎng)與形變速率的定量估計(jì),是對(duì)連續(xù)形變與地殼增厚形變模型的重要修正。結(jié)果并不支持塊體運(yùn)動(dòng)與東向逃逸模型,并認(rèn)為高原南北雙向俯沖模型中的塔里木塊體南向俯沖幾乎不存在。
[Abstract]:Since the 50~55 Ma since the collision between India and Eurasia Continental North after the formation of the Himalaya Tibet Plateau orogenic belt, resulting in a collision caused crustal thickening plateau uplift, changed the tectonic pattern of the Asian continental lithosphere, also have great influence on the regional climate and environment. The Altun fault as the main boundary faults of Northern Tibetan Plateau the kinematic properties, has attracted much attention in 1970s, the slip rate of different levels leads to the block movement and eastward escape and continuous deformation and crustal thickening in two kinds of endmember model. About 10~15 Ma to appear in the rift graben and Northern and southern Tibetan Plateau, plateau that provides evidence to the tension movement. Show that the Tibetan Plateau began to experience crustal thinning process of Tibetan Plateau. Since the formation of deformation field experience change, geology tectonic processes long time scale and the GP S 10~15 Ma whether the observations can be unified? Since the Qinghai Tibet Plateau crust thinning process caused by changes in elevation how? The northern margin of the Tibetan Plateau, especially across the Arkin fault with how the present 3-D crustal deformation field, the crustal strain is how the North Arkin fault, diffuse distribution between the lattice tower Qi and Arkin faults? The northern margin of the Tibetan Plateau how has the mechanical properties and the Tarim Basin, due to the influence of Arkin on how to cross fault deformation? Finally, GPS observed the surface deformation field to Qinghai Tibet Plateau deformation mode of argument to what answer? The scientific questions, has very important significance for the study of the uplift of the Tibetan Plateau and the deformation process this paper is divided into two parts. The first part is the observation and Study on the northern margin of the Tibetan Plateau three-dimensional interseismic motion field. In the northern margin of the Tibetan Plateau, the Elgin cross The central segment of the fault self 9 GPS continuous observation stations were carried out, according to the regional characteristics of the design of observation station unattended, with low cost, high quality of observation. The establishment of continuous GPS stations to fill the gaps in the northern margin of the Tibetan Plateau, especially the study and observation on crustal deformation the uninhabited areas, the accumulation of continuous GPS data precious; by the end of July 2015, a total of 4 years of continuous GPS observation data. The analysis results prove that the effective design of station method, GPS station observation data is stable, stable quality, continuity of data stability. Combined with the use of China continental environmental monitoring network in the study area and neighborhood GPS continuous stations data position time series and velocity field is obtained in the northern margin of the middle part of Tibetan Plateau across the Altyn fault of three dimension deformation. Using three-dimensional linear elastic backward sliding block motion model (backslip), The inversion of the Tarim block, North Altyn Tagh block, 3D block movement in the Qaidam block and Qimantag block. The results show that the North Altyn mountain relative to the Tarim Basin (1.32 + 0.2) mm/a uplift rate, relative to the Qaidam Basin is (0.73 + 0.3) mm/a uplift rate, can be interpreted as the north the block has significant orogenic process of the Altun fault; have (8.21 + 0.60) mm/a sinistral slip rate, (0.66 + 0.60) mm/a shortening rate; Qimantag fracture (0.53 + 0.60) mm/a sinistral slip rate, (1.53 + 0.60) mm/a shortening rate; North Altyn fault there is (0.87 + 0.60) mm/a l rate (0.69 + 0.60) shortening rate of mm/a. At the same time, the Altun fault, west two slip rate is basically the same, about 8.0~10.0mm/a. quantitative research results support the continuous deformation and crustal thickening model shows that the relative Tarim block, North Qinghai Tibet Plateau The edge area is uplift, thickening, north of Arkin mountain area is the most obvious, the Arkin fault uplift rate of about 1.3mm/a. across the northern margin of the Tibetan Plateau, the broad North Arkin fault and Qimantag fracture near the 200km deformation zone, shortening of the crust to North-South shortening is not obvious, only about 2.9mm, and nearly half of shortening occurred in the Qimantag mountains on the south side of the.GPS observation Arkin Che'erchen River fault (~86 ~ E) profile shows that the fracture deformation characteristics of non symmetry exists on both sides. This paper uses the asymmetric deformation profile data model GPS velocity inversion, obtain crust shear modulus difference on both sides of faults in the northern Tarim Basin and the Tibetan Plateau. The results showed that the crust of Tarim basin the shear modulus is about 1.53 times of the Northern Qinghai Tibet Plateau shear modulus, the corresponding S wave ratio value of 1.24, and Yang et al of the crust and upper mantle 3D VSV model results Consistent. Seismological research indicates that, in northern and Eastern Tibetan Plateau in the mid crust low velocity layer exists, the local area may occur in partial melting; Hacker further confirmed the Qiangtang block in the crust into the deep crustal melting phenomenon exists. This article uses completely different from seismological data, through the different mechanical properties of crust derived north the measurement method of the Qinghai Tibet Plateau and the Tarim Basin, and get seismology S wave ratio and its tectonic physics explain fairly consistent results. The results provide new constraints for the Qinghai Tibet Plateau mechanical evolution model. In the second part of this paper is to use the coverage of the Tibetan Plateau and its adjacent GPS velocity field, strain rate field calculation in the Tibet Plateau.GPS observation of velocity field not only shows the WNW crustal stretching process, also reveals the interior of the Qinghai Tibet Plateau more Add an important crust thinning process. The results showed that the northern and southern Tibetan Plateau vertical strain rate (thinning strain rate) respectively (8.9 + 0.8) nanostrain/a and (7.4 + 1.2) nanostrain/a, southwest of Qinghai Tibet Plateau vertical strain rate (12 + 3.2) nanostrain/a, consistency the interior of the Qinghai Tibet Plateau large scale strain rate measurement results. And the tensile strain rate observed within the Qinghai Tibet Plateau is also quite consistent, along the Northern Qinghai Tibet Plateau, N114 + 1 ~ E principal strain direction tensile strain rate (21.9 + 0.4) nanostrain/a; plateau south along the N93 + 1 ~ E the direction of strain tensile strain rate (16.9 + 0.2) nanostrain/a; Southwest of the plateau along the N74 + 3 ~ E principal strain direction tensile strain rate (22.2 + 1.8) nanostrain/a. if the crust thinning begins at 10~15 Ma, and the observed strain rate for the entire time span, so the crust The cumulative 5.5~8.5km. Airy crustal thinning using the equilibrium theory, the average elevation of the Qinghai Tibet Plateau will drop ~1km. in the northern Tibetan Plateau, South and southwest is similar to the vertical strain rate also shows that in the 3 regions of the crust, is faulting and crustal thinning process by the same physical mechanism dominated. The two part of the research results, found that the present Tibetan Plateau and vertical movement in the marginal area there is a great difference. The interior of the plateau region is experiencing crustal thinning, and the edge of the plateau region is experiencing a different degree of thickening and uplift of the northern Tibetan Plateau. The vertical strain rate is about 5~20nanostrain/a, if we consider the gravity equilibrium. The corresponding vertical uplift rate is about 0.04~0.14mm/a. However, in some areas such as the northern Altyn Tagh block, the bottom supported deflection plate inserted in the southern Tarim Basin, in the There is no gravity equilibrium, the vertical uplift rate may reach 1mm/a. in Himalaya area show different levels of vertical deformation, strong vertical strain (about 10~80nanostrain/a), the base of the mountains by inserted plate support India, assumed by the vertical strain rate estimation of uplift rate can not be balanced by gravity. But the subducting slab model bound by GPS and leveling data that uplift rate reached about 7mm/a. in the Qilian Mountains area, the GPS strain rate deduced vertical strain rate of about 20~40nanostrain/a, using the equilibrium theory, the average uplift rate is 0.15~0.3mm/a; and the thrust and fold deformation zone of the lower crust may still exist elastic deformation, can achieve complete gravity equilibrium, rising rate may be higher than the estimated actual uplift. This study gives different areas on the Qinghai Tibet Plateau 3D deformation field and strain The quantitative estimation of the rate is an important modification for the continuous deformation and the crustal thickening deformation model. The results do not support the block movement and the eastward escape model. It is considered that the South subduction of the Tarim block in the two way subduction model of plateau is almost nonexistent.

【作者單位】： 中國地震局地質(zhì)研究所;
【分類號(hào)】：P228.4;P315.7
【正文快照】： GPS觀測(cè)研究現(xiàn)今青藏高原地殼形變機(jī)制——來自阿爾金斷裂三維運(yùn)動(dòng)場(chǎng)及高原地殼減薄的證據(jù)@葛偉鵬$中國地震局地質(zhì)研究所!北京100029自50~55 Ma以來,印度次大陸向北與歐亞大陸碰撞后形成喜馬拉雅—青藏高原造山帶,碰撞導(dǎo)致地殼增厚致使高原大幅隆升,改變了亞洲大陸巖石圈的構(gòu)

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本文編號(hào)：1411492