【摘要】：中國(guó)東部由中國(guó)東北地區(qū)(中亞造山帶東段)、華北克拉通、蘇魯造山帶及華南地塊構(gòu)成,地處歐亞板塊東南部,緊鄰西太平洋俯沖帶。受太平洋板塊西向俯沖的影響,該區(qū)有著復(fù)雜的地質(zhì)構(gòu)造背景和深部結(jié)構(gòu)特征,研究該區(qū)上地幔頂部的結(jié)構(gòu)有助于我們更好地理解在大陸動(dòng)力演化過(guò)程中深部對(duì)淺層結(jié)構(gòu)的影響。早期的結(jié)果主要應(yīng)用了來(lái)自地震觀測(cè)報(bào)告(中國(guó)地震年報(bào)及各省區(qū)域臺(tái)網(wǎng)觀測(cè)報(bào)告)的Pn到時(shí)資料,最近的研究除了利用地震觀測(cè)報(bào)告的資料外,主要補(bǔ)充了中國(guó)西部特別是青藏高原流動(dòng)地震臺(tái)陣記錄的Pn到時(shí)數(shù)據(jù),重點(diǎn)研究了中國(guó)西部地區(qū)上地幔頂部的速度結(jié)構(gòu)和各向異性。本文收集了 ISC (國(guó)際地震中心)報(bào)告、中國(guó)地震年報(bào)和中國(guó)區(qū)域地震臺(tái)網(wǎng)觀測(cè)報(bào)告的Pn到時(shí)資料,并截取了中國(guó)東北、華北流動(dòng)臺(tái)陣和區(qū)域臺(tái)網(wǎng)記錄的地震事件,同時(shí)專門挑選了華南地區(qū)固定臺(tái)站記錄的該區(qū)中小地震事件,由專業(yè)人員對(duì)這些事件手動(dòng)拾取了大量高精度的Pn波到時(shí)數(shù)據(jù),最終挑選出24072次地震的240814條Pn波到時(shí)數(shù)據(jù),這些數(shù)據(jù)是由區(qū)域內(nèi)2049個(gè)臺(tái)站記錄的。本研究大量數(shù)據(jù)的應(yīng)用使Pn射線密集覆蓋了整個(gè)中國(guó)東部地區(qū)。我們采用Pn波層析成像方法反演獲得了中國(guó)東部及其鄰區(qū)上地幔頂部Pn波速度結(jié)構(gòu)及各向異性,并對(duì)反演結(jié)果的分辨率進(jìn)行了詳細(xì)的測(cè)試。結(jié)果表明,中國(guó)東部地區(qū)上地幔頂部平均速度為8.06 km/s,速度變化范圍為7.81-8.32 km/s。東北地區(qū)東部表現(xiàn)為顯著的低速異常,可能是受太平洋板塊俯沖的影響并代表長(zhǎng)白山火山區(qū)上涌的熱物質(zhì);華北克拉通中、東部Pn呈現(xiàn)低速,而西部地區(qū)則表現(xiàn)為高速異常,這或許說(shuō)明西部的鄂爾多斯為穩(wěn)定的塊體,而中東部區(qū)域則經(jīng)歷了破壞或改造;穩(wěn)定的華南地塊主體表現(xiàn)為高速。反演結(jié)果還揭示小型的江漢盆地、下遼河盆地、二連及海拉爾盆地都顯示出高速,而大型的四川盆地和松遼盆地內(nèi)部則呈現(xiàn)出不均勻的結(jié)構(gòu)特征。四川盆地的高速異常顯示出明顯的分塊現(xiàn)象,這可能是該盆地在沉積前具有不同的基底物質(zhì);松遼盆地的北部呈現(xiàn)為高速,而南部卻表現(xiàn)為低速異常,這可能意味著該盆地南部的巖石圈已經(jīng)遭受了改造。上述盆地的細(xì)結(jié)構(gòu)特征與重力異常和大地?zé)崃餮芯肯辔呛?由此說(shuō)明本研究獲得了較高分辨率的結(jié)果。本研究進(jìn)一步揭示Pn各向異性與速度結(jié)構(gòu)的分布存在一定的關(guān)聯(lián),Pn波低速區(qū)和高低速過(guò)渡帶的各向異性也較為強(qiáng)烈,而大部分強(qiáng)震都發(fā)生在這些區(qū)域之上的地殼內(nèi),可能說(shuō)明這些部位容易發(fā)生變形而應(yīng)力集中或產(chǎn)生應(yīng)力差。一些盆地附近的Pn各向異性較為強(qiáng)列,這可能反映了盆地演化過(guò)程中的伸展構(gòu)造背景。
[Abstract]:The eastern part of China is composed of northeast China (eastern section of Central Asian orogenic belt), North China Craton, Sulu orogenic belt and South China block. It is located in the southeast of Eurasian plate and adjacent to the western Pacific subduction zone. Influenced by the westward subduction of the Pacific plate, the area has complicated geological tectonic setting and deep structural characteristics. The study of the structure of the top of the upper mantle in this area is helpful for us to better understand the influence of the deep layer on the shallow structure in the process of continental dynamic evolution. The early results mainly used the Pn time data from the seismological report (China earthquake Annual report and the observation report of the regional network of various provinces). In addition to using the data from the seismic observation report, recent studies have been carried out. This paper mainly supplements the Pn time data recorded by the mobile seismic array in western China, especially the Qinghai-Tibet Plateau, and focuses on the velocity structure and anisotropy of the upper mantle in the western part of China. In this paper, the Pn time data of ISC (International Seismic Center) report, China earthquake Annual report and China Regional Seismic Network observation report are collected, and the earthquake events recorded by Northeast China, North China Mobile Array and Regional Seismic Network are intercepted. At the same time, the small and medium earthquake events recorded by the fixed stations in South China were specially selected. A large number of high-precision Pn wave arrival data were manually picked up by professionals for these events, and finally 240814 Pn wave arrival data of 24072 earthquakes were selected. These data are recorded by 2049 stations in the region. The application of a large amount of data in this study results in the intensive coverage of Pn rays throughout eastern China. The velocity structure and anisotropy of Pn wave at the top of the upper mantle in eastern China and its adjacent regions are obtained by using Pn wave tomography method. The resolution of the inversion results is measured in detail. The results show that the average velocity of the upper mantle in eastern China is 8.06 km/s, ranging from 7.81-8.32 km/s.. In the eastern part of Northeast China, there is a significant low velocity anomaly, which may be influenced by the subduction of the Pacific plate and represent the upwelling heat material in the Changbai Mountains. In the North China Craton, the Pn in the east shows a low velocity, while in the western region, it shows a high velocity anomaly. This may indicate that Ordos in the west is a stable block, while the central and eastern regions have undergone destruction or transformation, while the main body of the stable South China block is characterized by high speed. The inversion results also reveal that the small Jianghan basin, the lower Liaohe basin, the Erlian basin and the Hailar basin all show high speed, while the large Sichuan basin and the Songliao basin show uneven structural characteristics. The high speed anomaly of Sichuan basin shows obvious fragmentation phenomenon, which may be that the basin has different basement materials before sedimentation, while the north of Songliao basin presents high speed, while the south shows low velocity anomaly. This may mean that the lithosphere in the southern part of the basin has been transformed. The fine structure of the basin is consistent with the gravity anomaly and the study of the geothermal flow, which shows that the results obtained in this study are of high resolution. The present study further reveals that there is a certain correlation between the Pn anisotropy and the distribution of velocity structure. The anisotropy of the low velocity region of PN wave and the transition zone of high and low velocity is also strong, and most of the strong earthquakes occur in the crust above these regions. It may indicate that these parts are prone to deformation and stress concentration or stress difference. The Pn anisotropy near some basins is relatively strong, which may reflect the extensional tectonic background during the evolution of the basin.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)(北京)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P315.2

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