本文關(guān)鍵詞：地球介質(zhì)衰減特性層析成像　出處：《中國(guó)地震局地球物理研究所》2016年博士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 地方震層析成像 地震波衰減 衰減特性層析成像 背景噪聲 水庫(kù)庫(kù)區(qū) 中國(guó)大陸 地球介質(zhì)

【摘要】：與地震波衰減直接相關(guān)聯(lián)的介質(zhì)品質(zhì)因子Q值描述了地球介質(zhì)的非彈性和非均勻性,是了解地下裂隙的數(shù)量、孔隙密度與分布以及孔隙中存在的流體含量的重要參數(shù)。測(cè)定衰減的橫向變化不僅能為了解地下熱結(jié)構(gòu)、粘性和流變特性提供額外約束,更重要的是對(duì)于解釋三維速度結(jié)構(gòu)有重要意義,是理解地震波速度和地球介質(zhì)密度橫向不均勻分布的重要參數(shù)。本論文基于不同類型的地震波形數(shù)據(jù),采用層析成像的方法進(jìn)行了不同尺度介質(zhì)衰減結(jié)構(gòu)的研究。首先基于地方震數(shù)據(jù)在3個(gè)典型水庫(kù)庫(kù)區(qū)進(jìn)行了小區(qū)域三維精細(xì)衰減結(jié)構(gòu)層析成像的研究,通過衰減結(jié)構(gòu)的分布評(píng)估了地下流體的滲透和擴(kuò)散狀態(tài)。其中在紫坪埔水庫(kù)庫(kù)區(qū),本論文通過汶川Ms8.0地震前后的三維衰減結(jié)構(gòu)推斷了紫坪埔水庫(kù)庫(kù)水滲透和擴(kuò)散在Ms8.0地震發(fā)生發(fā)展過程中的可能作用。然后利用Lg波在新疆地區(qū)開展了區(qū)域尺度的衰減結(jié)構(gòu)成像,得到了新疆地區(qū)高分辨率的Lg波衰減結(jié)構(gòu)圖像。最后分別基于中短周期地震面波和背景噪聲面波,開展了中國(guó)大陸大尺度的衰減結(jié)構(gòu)層析成像,通過改進(jìn)振幅提取技術(shù),極大的提高了計(jì)算效率。其中,利用背景噪聲面波進(jìn)行衰減結(jié)構(gòu)成像的研究系首次基于完整的理論體系將背景噪聲互相關(guān)技術(shù)應(yīng)用于衰減結(jié)構(gòu)成像中,并系統(tǒng)形成了背景噪聲面波衰減結(jié)構(gòu)成像的完整數(shù)據(jù)處理和計(jì)算程序,進(jìn)而將該方法應(yīng)用于中國(guó)大陸地區(qū)得到了研究區(qū)高分辨率的背景噪聲面波衰減圖像。地方震層析成像是研究小區(qū)域典型構(gòu)造區(qū)介質(zhì)結(jié)構(gòu)的主要方法,廣泛應(yīng)用于斷層帶、俯沖帶、火山區(qū)和水庫(kù)庫(kù)區(qū)。尤其在水庫(kù)庫(kù)區(qū),地方震成像技術(shù)是研究地下流體分布和狀態(tài)的重要方法,是推斷地震活動(dòng)與地殼結(jié)構(gòu)的精細(xì)關(guān)系以及地震發(fā)生機(jī)理的重要依據(jù)。水庫(kù)庫(kù)區(qū)地殼介質(zhì)中孔隙流體的滲透和擴(kuò)散是水庫(kù)誘發(fā)地震的一個(gè)重要原因,是研究水庫(kù)誘發(fā)地震的成因機(jī)理和進(jìn)一步判定水庫(kù)誘發(fā)地震危險(xiǎn)性的重要參數(shù)。將速度(VP)、波速比(VP/Vs)和衰減(Q值)結(jié)構(gòu)成像相結(jié)合是分辨由于結(jié)構(gòu)不連續(xù)或流體滲透導(dǎo)致的地下結(jié)構(gòu)變化的最重要方法。本論文利用地方震成像技術(shù)在龍灘、三峽、紫坪鋪三座大型水庫(kù)庫(kù)區(qū)開展了三維速度、波速比與衰減結(jié)構(gòu)層析成像的研究。三個(gè)庫(kù)區(qū)高分辨率的三維速度、波速比與衰減圖像均揭示了水庫(kù)庫(kù)區(qū)周圍介質(zhì)的復(fù)雜性以及流體滲透對(duì)介質(zhì)結(jié)構(gòu)存在的影響,其中流體在庫(kù)區(qū)下方斷裂帶中的滲透和擴(kuò)散可能是地震發(fā)生的重要起點(diǎn)。龍灘和三峽庫(kù)區(qū)的介質(zhì)結(jié)構(gòu)顯示,庫(kù)區(qū)下方淺層存在明顯的低VP,高VP/VS,低QP和低Qs分布特征,表明淺層介質(zhì)發(fā)生了明顯的流體滲透現(xiàn)象。龍灘水庫(kù)庫(kù)首區(qū)和主要河流下方的低VP,高VP/Vs,低QP和低Qs的異常深度達(dá)到了4-7km左右,表明龍灘水庫(kù)的庫(kù)水滲透深度可能達(dá)到了4-7km。三峽水庫(kù)庫(kù)區(qū)的仙女山斷裂周圍流體的滲透可能達(dá)到6km左右,其他主要河流下方的庫(kù)水滲透可能只有2km左右。紫坪鋪水庫(kù)庫(kù)區(qū)的三維Vp,Vp/Vs,Qp和Qs圖像表明紫坪鋪水庫(kù)的庫(kù)水滲透深度可能達(dá)到了10km以上,可能與水庫(kù)周圍存在深大斷裂有關(guān)。我們推斷紫坪鋪水庫(kù)的庫(kù)水滲透有可能是汶川Ms8.0地震發(fā)生的觸發(fā)因素,進(jìn)一步的證據(jù)需要結(jié)合水庫(kù)蓄水前的三維介質(zhì)結(jié)構(gòu)進(jìn)行更深入研究。汶川地震后,紫坪埔水庫(kù)下方的高衰減區(qū)進(jìn)一步擴(kuò)大,表明該地震使得震源區(qū)周圍的介質(zhì)發(fā)生了明顯破裂,流體沿?cái)鄬雍土严哆M(jìn)一步滲透和擴(kuò)散,導(dǎo)致高衰減區(qū)的范圍比震前更大,深度更深。Lg波是區(qū)域范圍內(nèi)地震波中能量最強(qiáng)、振幅最大、在地震圖上表現(xiàn)最為突出的震相,因此Lg波Q值成像是了解區(qū)域構(gòu)造特征并尋找介質(zhì)異常區(qū)的重要手段。本論文基于Lg波,對(duì)新疆及鄰近地區(qū)開展了區(qū)域尺度的衰減結(jié)構(gòu)成像。Lg波衰減圖像顯示,QLg的分布形態(tài)與研究區(qū)地質(zhì)構(gòu)造緊密相關(guān)。帕米爾高原東北緣、青藏高原西北緣、南天山西段、北天山及其北緣的準(zhǔn)噶爾盆地內(nèi)部區(qū)域?qū)儆诘蚎0區(qū),塔里木盆地西部、塔里木盆地東部、包括吐魯番-哈密盆地的東天山、南天山東段以及北天山都屬于高Q0區(qū)。根據(jù)研究區(qū)QLg值分布圖像與地形的明顯相關(guān)性,我們認(rèn)為L(zhǎng)g波具有明顯的通道波特征。并由塔里木盆地和準(zhǔn)噶爾盆QLg分布圖像的分區(qū)性推斷這兩個(gè)大型剛性盆地內(nèi)部可能存在隱伏斷裂。由于面波的優(yōu)勢(shì)周期比體波大,因此面波主要對(duì)較大尺度的構(gòu)造特征有較好的采樣。在地震圖中超過一定的震中距范圍,面波的能量往往很大,且在地球表面衰減較慢,對(duì)臺(tái)站覆蓋較差的區(qū)域也可能得到較高分辨率的成像結(jié)果。因此,面波層析成像是了解大尺度構(gòu)造特征的重要數(shù)據(jù),在少震區(qū)和臺(tái)站密度相對(duì)較低的地區(qū)也同樣適用。本論文基于中國(guó)大陸國(guó)家地震臺(tái)網(wǎng)和區(qū)域臺(tái)網(wǎng)的188個(gè)寬頻帶臺(tái)站的10s和20s周期的地震瑞利面波,在相匹配濾波的基礎(chǔ)上,提取了瑞利面波振幅比,并基于雙臺(tái)譜比的方法反演了中國(guó)大陸10s和20s面波的衰減結(jié)構(gòu)圖像。我們開發(fā)了自動(dòng)測(cè)定地震振幅譜的方法,并與手動(dòng)測(cè)定的方法進(jìn)行了對(duì)比,結(jié)果具有較好的一致性,大大提高了計(jì)算效率,實(shí)現(xiàn)了使用雙臺(tái)法基于大量地震數(shù)據(jù)反演得到了中國(guó)大陸高分辨率的二維衰減結(jié)構(gòu)模型。在中國(guó)大陸中東部地區(qū)模型的分辨率達(dá)到了3°左右,在西部和中國(guó)大陸邊緣地區(qū),模型的分辨率在5°左右。本論文的成像結(jié)果與已有的中國(guó)大陸衰減結(jié)構(gòu)的分布具有較好的相似性,與地質(zhì)構(gòu)造特征也具有較好的對(duì)應(yīng)關(guān)系。近年來,噪聲面波成像技術(shù)得到了飛速發(fā)展,擺脫了地震面波成像對(duì)地震定位和震源機(jī)制的影響,并不受地震發(fā)生無規(guī)律的限制。噪聲面波成像已廣泛應(yīng)用于速度結(jié)構(gòu)反演。由于背景噪聲源的強(qiáng)度和分布隨時(shí)間、位置和方向變化的復(fù)雜性,從背景噪聲互相關(guān)中提取振幅進(jìn)而進(jìn)行衰減結(jié)構(gòu)的研究要遠(yuǎn)遠(yuǎn)落后于速度結(jié)構(gòu)的研究。本論文首先基于數(shù)值模擬數(shù)據(jù)開展了從背景噪聲互相關(guān)中提取面波振幅并反演介質(zhì)衰減系數(shù)的測(cè)試,表明可以從temporal flattening后的數(shù)據(jù)中正確提取瑞利波衰減。此后詳細(xì)闡述了從背景噪聲中提取瑞利波振幅的整個(gè)過程,并介紹了一種改進(jìn)的temporal flattening方法。通過與實(shí)際地震面波中提取的衰減系數(shù)對(duì)比,我們認(rèn)為從背景噪聲中提取振幅計(jì)算一維衰減結(jié)構(gòu)的方法是可行的。在此基礎(chǔ)上,本論文進(jìn)一步開展了二維衰減結(jié)構(gòu)模型層析成像的研究�；诟飨虍愋缘脑肼曉捶植己筒痪鶆蛩p結(jié)構(gòu)模型,利用數(shù)值模擬的方法產(chǎn)生了100個(gè)臺(tái)站長(zhǎng)時(shí)間的背景噪聲記錄。采用180kmm和60km兩種尺度的網(wǎng)格節(jié)點(diǎn)間距對(duì)研究區(qū)進(jìn)行網(wǎng)格化,在兩種尺度下進(jìn)行了二維衰減結(jié)構(gòu)層析成像。反演得到的衰減模型與設(shè)定的初始模型基本一致。檢測(cè)板測(cè)試的結(jié)果也顯示,本論文中提出的噪聲面波振幅的提取方法和參數(shù)設(shè)置可以成功的反演二維衰減結(jié)構(gòu)模型。最后,我們使用國(guó)家臺(tái)網(wǎng)和區(qū)域臺(tái)網(wǎng)146個(gè)寬頻帶地震臺(tái)站記錄的真實(shí)的背景噪聲數(shù)據(jù),開展了中國(guó)大陸噪聲面波衰減結(jié)構(gòu)成像的研究。首先利用窄帶濾波和異步temporal flattening等方法對(duì)背景噪聲數(shù)據(jù)進(jìn)行處理。通過噪聲互相關(guān),得到了10s和20s周期的1萬多條臺(tái)站對(duì)間的瑞利波經(jīng)驗(yàn)格林函數(shù),利用相匹配濾波技術(shù)和雙臺(tái)成像方法反演了10s和20s周期的瑞利波衰減圖像。其中新疆西南部、青藏高原西部、東部地區(qū)和研究區(qū)其他的邊緣地區(qū)的圖像分辨率在2.5°-5°之間,其他地區(qū)衰減圖像的分辨率達(dá)到了2.5°左右。衰減圖像與地質(zhì)構(gòu)造特征具有較好的對(duì)應(yīng)性,與中國(guó)大陸已有的地震面波衰減結(jié)構(gòu)圖像也具有較好的一致性。表明利用真實(shí)的地震背景噪聲記錄,從背景噪聲互相關(guān)中提取瑞利波振幅,并進(jìn)行二維瑞利波衰減結(jié)構(gòu)層析成像是可行的,為面波衰減結(jié)構(gòu)層析成像的研究提供了另一條途徑,擺脫了對(duì)地震發(fā)生的依賴且可以提高衰減圖像的分辨率,具有重要的應(yīng)用價(jià)值。
[Abstract]:The medium quality factor Q, which is directly related to seismic attenuation, describes the inelasticity and non-uniformity of the earth's medium. It is an important parameter to understand the number, density and distribution of underground fissure, and the fluid content existing in the pores. The lateral variation of attenuation can not only provide additional constraints for understanding the underground thermal structure, viscosity and rheological properties, but also is important for explaining three-dimensional velocity structure, and is an important parameter to understand the lateral heterogeneity of seismic wave velocity and earth medium density. Based on different types of seismic waveform data, this paper uses the method of tomography to study the dielectric attenuation structure of different scales. Firstly, based on local seismic data, three dimensional fine attenuation structure tomography is studied in 3 typical reservoir areas, and the permeability and diffusion state of underground fluid is evaluated through the distribution of attenuation structure. In the Zipingpu Reservoir area, this paper deduces the possible role of reservoir infiltration and diffusion of Zipingpu Reservoir in the occurrence and development of Ms8.0 earthquake through the three-dimensional attenuation structure before and after the Wenchuan Ms8.0 earthquake. Then Lg wave is used in Xinjiang area to carry out the region scale attenuation structure imaging, and the high resolution Lg wave attenuation structure image of Xinjiang region is obtained. Finally, based on the Mid short period seismic surface wave and the background noise surface wave, we carried out the large-scale attenuation structure tomography in mainland China, and improved the amplitude extraction technology, which greatly improved the computation efficiency. Among them, the background noise of surface wave attenuation imaging system structure for the first time a complete theoretical system based on the cross-correlation technique applied to background noise attenuation structure imaging, and formed a complete system of data structure of image background noise attenuation of surface wave processing and calculation program, then this method is applied to the China mainland has been studied the background noise of high resolution surface wave attenuation image. Local seismic tomography (local seismic tomography) is the main method to study the medium structure of typical regional tectonic zones. It is widely used in fault zone, subduction zone, volcanic area and reservoir area. Especially in reservoir area, local seismic imaging technology is an important way to study the distribution and state of underground fluid, and it is an important basis for inferring the fine relationship between seismic activity and crustal structure and the mechanism of earthquake occurrence. The infiltration and diffusion of pore fluid in the crustal medium of reservoir area is an important reason for reservoir induced earthquake. It is an important parameter for studying the mechanism of reservoir induced earthquake and further determining the risk of reservoir induced earthquake. The combination of velocity (VP), wave velocity ratio (VP/Vs) and attenuation (Q) structure imaging is the most important way to distinguish the change of underground structure due to structural discontinuity or fluid penetration. In this paper, the Three Gorges, Longtan Reservoir Zipingpu three large reservoirs on the three-dimensional velocity, wave velocity and attenuation structure tomography using local seismic imaging technology. The three area high resolution three-dimensional velocity, wave velocity ratio and attenuation images reveal the complexity of the surrounding medium reservoir and fluid infiltration effect on dielectric structure exists, where the fluid permeability reservoir beneath the fault zone and the diffusion may be an important starting point of the earthquake. The medium structure in Longtan and Three Gorges Reservoir area shows that there are obvious low VP, high VP/VS, low QP and low Qs distribution characteristics in the shallow layer below the reservoir area, which indicates that obvious fluid penetration phenomenon occurs in shallow media. The depth of low VP, high VP/Vs, low QP and low Qs of the Longtan Reservoir head and main river reaches about 4-7km, indicating that the reservoir depth of Longtan Reservoir can reach 4-7km. The seepage of the fluid around the fault of the fairy mountain in the reservoir area of the Three Gorges reservoir may reach about 6km, and the permeability of the reservoir water below the other main rivers may be only about 2km. The 3D Vp, the Zipingpu Reservoir Region of Vp/Vs, Qp and Qs images show that the depth of penetration of Zipingpu Reservoir water could reach more than 10km, and there are deep faults around the reservoir on the. We conclude that the Zipingpu Reservoir water permeability may be associated with the Wenchuan Ms8.0 earthquake triggering factors, further evidence of the need to combine three-dimensional medium reservoir structure in front of a more in-depth study. After the Wenchuan earthquake, the high attenuation area below the Zipingpu Reservoir further expanded, indicating that the earthquake caused the obvious rupture of the surrounding media, and the fluid further penetrated and diffused along the fault and fissure, resulting in the range of high attenuation area larger and deeper than that before the earthquake. The Lg wave is the most powerful seismic phase in the region, with the largest amplitude and the most prominent phase on the seismic map. Therefore, the Lg wave Q value imaging is an important way to understand the regional structural characteristics and find out the abnormal area of the medium. Based on the Lg wave, the attenuated structural imaging of regional scale is carried out in Xinjiang and adjacent areas. The Lg wave attenuation image shows that the distribution of QLg is closely related to the geological structure of the study area. Junggar basin, northeastern Pamir Plateau of the northwest of Qinghai Tibet Plateau, southern Shanxi, the northern margin of the North Tianshan Mountain and its belongs to the low Q0 zone in the Western Tarim Basin, Eastern Tarim Basin, including Turpan - Hami basin, East Tianshan, South and north section of Shandong mountain area belongs to the high Q0 days. According to the obvious correlation between the QLg value distribution image and the terrain in the study area, we think that the Lg wave has obvious channel wave characteristics. It is also deduced from the QLg distribution of the Tarim Basin and the Junggar basin that there may be hidden faults in the two large rigid basins. As the dominant period of the surface wave is larger than that of the body wave, the surface wave is mainly sampled for the structural features of the larger scale. Over a certain range of epicentral distances in an seismograph, the energy of the surface waves is often very large, and the attenuation of the earth's surface is slow, and the areas with poor coverage of the station may also be obtained.
【學(xué)位授予單位】：中國(guó)地震局地球物理研究所
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：P315.6
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本文編號(hào)：1347196