【摘要】：地震波是照亮地球內部的一盞明燈,利用地震波研究地球內部結構、狀態(tài)、和演化是目前了解地球內部情況的最主要方法[1]。隨著地震學的不斷發(fā)展,人們不再滿足于依靠天然地震被動的研究地球內部情況,而是更多的依靠人工震源向地下發(fā)射地震波,主動的對地球內部進行探測[2]。進行這樣的主動震源探測是研究介質特性、斷層結構、地震預測預報等方面的重要技術途徑。大容量氣槍震源具有能量大、低頻成分豐富、傳播距離遠和環(huán)保高效等優(yōu)點,是探測地球內部的理想主動震源[3-4]。本文簡要介紹了新疆呼圖壁氣槍震源發(fā)射臺的建設過程、信號激發(fā)、大容量氣槍震源的震源特性、信號特征等,并利用新疆數(shù)字地震臺網(wǎng)接收到的呼圖壁氣槍發(fā)射臺激發(fā)的地震信號,采用疊加、互相關等方法,初步研究了大容量氣槍震源的震相特征,信號衰減特征和走時變化特征。得到以下結論:(1)新疆呼圖壁大容量氣槍發(fā)射臺激發(fā)的信號主要頻率集中在2-6Hz,6條氣槍一次同時激發(fā)產生的能量相當于一次ML0.9級天然地震產生的能量。通過對信號進行疊加,最遠可在距離氣槍震源380km處的臺站,發(fā)現(xiàn)氣槍信號。(2)對以氣槍震源為中心,400km為半徑范圍內的臺站接收到的氣槍信號進行疊加,并以6km/s的速度對信號進行折合,從折合走時剖面上發(fā)現(xiàn)氣槍震源激發(fā)的信號,在200km以外出現(xiàn)的Pn波,而且在傳播距到達200km以上后,氣槍震源與天然地震的走時趨于同步。(3)選取北天山地區(qū)8個臺站,對接收到的氣槍震源信號進行疊加,計算各個臺站疊加后的氣槍震源信號2-6Hz之間的P波和S波振幅譜的均方根,作為地震波傳播至該臺站的振幅值,并對振幅衰減特征進行擬合,得出北天山地區(qū)的Qp=464±70和Qs=653±46。(4)把各個臺站經(jīng)過反卷積計算去除了震源影響后的信號進行波形干涉,測量得到各個臺站特定震相的走時變化。以STZ臺數(shù)據(jù)為例,發(fā)現(xiàn)在2013年8月30日烏魯木齊MS5.1地震前走時變化表現(xiàn)為上升趨勢,經(jīng)過一段平穩(wěn)期后,走時變化呈現(xiàn)下降趨勢。初步分析可能是由于地震前應力積累產生的裂隙,地震后應力釋放裂隙還原造成的。在內陸地區(qū)應用大容量氣槍震源對地殼介質變化進行監(jiān)測,是地震學領域中的一項新的嘗試,為今后地下介質動態(tài)觀測和地下4D云圖的繪制打下了基礎。
[Abstract]:Seismic wave is a bright lamp that illuminates the earth's interior. Using seismic wave to study the structure, state and evolution of the earth's interior is the most important method to understand the earth's interior situation at present [1]. With the continuous development of seismology, people are no longer satisfied to rely on natural earthquakes passively to study the internal conditions of the earth, but more rely on artificial seismic sources to launch seismic waves into the ground, active exploration of the earth's interior [2]. Such active source detection is an important technical way to study the characteristics of medium, fault structure, earthquake prediction and prediction. The large capacity air gun source has the advantages of large energy, rich low frequency components, long propagation distance and environmental protection and high efficiency. It is an ideal active source for detecting the earth's interior [3-4]. This paper briefly introduces the construction process, signal excitation, source characteristics and signal characteristics of the Hutubi air gun source transmitter in Xinjiang. Using the seismic signals generated by the Hutubi air gun emitter received by the Xinjiang Digital Seismograph Network, the seismic phase characteristics, signal attenuation characteristics and travel time variation characteristics of the large capacity air gun source are preliminarily studied by means of superposition, cross-correlation and so on. The following conclusions are obtained: (1) the main frequency of the signal generated by the large capacity air gun emitter in Hutubi Xinjiang is mainly concentrated in the energy generated by the simultaneous excitation of two to six gas guns equal to the energy generated by a natural earthquake of magnitude ML0.9. By superposing the signals, the air gun signals can be found as far away from the air gun source as 380km. (2) the air gun signals received by the stations with the air gun source as the center and the 400km as the radius range are superimposed. The signal is converted at the velocity of 6km/s, and the signal generated by the air gun source is found on the profile of the commutative travel time, and the Pn wave appears outside the 200km, and after the propagation distance reaches above 200km, The travel time of the air gun source and the natural earthquake tend to synchronize. (3) eight stations in the North Tianshan region are selected to stack the received air gun source signals. The root mean square (RMS) of P wave and S wave amplitude spectrum between the air gun source signal 2-6Hz is calculated, which is used as the amplitude value of the seismic wave propagating to the station, and the attenuation characteristic of the amplitude is fitted. It is concluded that the Qp=464 鹵70 and Qs=653 鹵46. (4) the signal of each station is interfered by the signal after deconvolution calculation and the specific phase of each station is measured. Taking the data of STZ station as an example, it is found that the change of walking time shows an upward trend before the MS5.1 earthquake in Urumqi on August 30, 2013. After a period of steady period, the change of walking time shows a downward trend. The preliminary analysis may be caused by the crack caused by the accumulation of stress before the earthquake and the reduction of the fissure released by the stress after the earthquake. It is a new attempt in the field of seismology to monitor the crustal medium change by using large capacity air gun source in inland area, which lays a foundation for the dynamic observation of underground medium and the drawing of underground 4D cloud map in the future.
【學位授予單位】：中國地震局蘭州地震研究所
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P631.44

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本文編號：2307914