利用模板匹配方法研究稀疏臺站地區(qū)地震活動性
發(fā)布時間：2018-09-01 09:32
【摘要】：地震目錄是發(fā)震構(gòu)造確認(rèn)、地震活動性分析的基礎(chǔ)資料。然而由于強震尾波的干擾、地震事件震級較小、臺站分布稀疏等原因,會造成地震目錄的嚴(yán)重缺失,從而影響以地震目錄為基礎(chǔ)的地震活動性分析等的可靠分析。目前,以互相關(guān)技術(shù)為基礎(chǔ)的模板匹配方法是低信噪比情況下檢測遺漏事件的有效方法,且已經(jīng)得到了廣泛應(yīng)用。本文利用模板匹配方法,針對以下兩個問題,進行了相關(guān)研究。一、2014年8月3日在云南省魯?shù)榭h發(fā)生了Ms6.5地震。魯?shù)榈卣鹬?關(guān)于魯?shù)榈卣鹗欠裼上宥伤畮煲鸫嬖谝恍幾h。根據(jù)前人研究表明,分析中強地震前后地震活動性可以為判斷主震起源提供一定的依據(jù)。然而,由于魯?shù)榈卣鹫鹬懈浇潭ㄅ_站分布稀疏及主震后尾波干擾等因素的影響會造成地震目錄的缺先從而可能影響地震活動性的可靠分析。本文采用模板匹配方法,以臺網(wǎng)目錄中的541個事件作為模板對魯?shù)榈卣鹎昂笮〉卣疬M行了搜索和識別,得到以下結(jié)果：(1)在主震之前33天到主震后5天的連續(xù)波形中識別出991個未在目錄中列出的地震,使余震的完備震級從1.8降低到1.3。并根據(jù)檢測目錄得到主震前33天內(nèi)的b值為1.04±±0.18,余震的b值在震后5天內(nèi)由0.5左右逐漸上升至0.9附近并保持穩(wěn)定。(2)根據(jù)2009年到主震發(fā)生前的臺網(wǎng)目錄得到該區(qū)域的背景b值為0.93±0.04。即魯?shù)榈卣鹎昂髤^(qū)域地震活動b值均與背景b值接近,這與典型水庫誘發(fā)的中強震具有的b值特征不相符。(3)通過進一步分析臺網(wǎng)目錄,未發(fā)現(xiàn)溪洛渡水庫蓄水前后研究區(qū)域內(nèi)的地震活動性存在明顯變化,這也與典型水庫誘發(fā)地震區(qū)域的地震活動性特征不相符。二、2015年4月15日在內(nèi)蒙古自治區(qū)阿拉善左旗發(fā)生Ms5.8地震。由于臺網(wǎng)目錄中地震事件較少,且震中附近固定臺站分布稀疏可能會造成臺網(wǎng)目錄所提供的震源位置誤差偏大,因此很難從臺網(wǎng)目錄提供的震源位置判斷發(fā)震構(gòu)造。本文利用模板匹配方法,采用震中附近幾個流動臺的數(shù)據(jù),以臺網(wǎng)目錄中的55個事件作為模板事件對阿拉善地震前后的遺漏事件進行了搜索和識別,并結(jié)合Hypo2000和HypoDD,對此次地震的發(fā)震構(gòu)造進行了初步的分析。主要結(jié)論如下：(1)在主震之前10天到主震后10天的連續(xù)波形中識別出362個為遺漏事件；(2)采用Hypo2000對臺網(wǎng)目錄中的55個事件進行了重定位,重定位后震源位置的水平和垂直方向理論平均誤差分別為2.50km和36.9km,理論平均走時殘差為0.58s;(3)通過互相關(guān)技術(shù)提取遺漏事件P、S到時,結(jié)合HypoDD對遺漏事件進行了重定位。重定位后震中優(yōu)勢分布近東西向(最小二乘擬合得優(yōu)勢走向為261.4°),與USGS給出的震源機制解中節(jié)面Ⅱ的走向(262°)基本一致。另外從震源深度由淺及深的趨勢可以看出,余震分布具有較大傾角的特征。通過參考不同研究機構(gòu)和學(xué)者所得震源機制,我們認(rèn)為2015年阿拉善Ms5.8地震的發(fā)震構(gòu)造為一條走向約261°,高傾角的左旋走滑斷層。
[Abstract]:Earthquake catalogue is the basic data for confirmation of seismogenic structure and analysis of seismicity. However, due to the interference of strong coda waves, small magnitude of earthquake events, sparse distribution of stations and other reasons, it will cause serious deficiency of earthquake catalogue, thus affecting the reliable analysis of seismicity based on earthquake catalogue. The template matching method based on this method is an effective method to detect missing events under low signal-to-noise ratio and has been widely used. In this paper, template matching method is used to solve the following two problems. First, the Ms6.5 earthquake occurred in Ludian County, Yunnan Province on August 3, 2014. After the Ludian earthquake, the Ludian earthquake is considered to be an earthquake. According to previous studies, the analysis of seismicity before and after moderate earthquakes can provide a certain basis for judging the origin of the main earthquake. However, due to the sparse distribution of fixed stations near the epicenter of the Ludian earthquake and the interference of coda waves after the main earthquake, the earthquake catalogue will be absent. In this paper, a template matching method is used to search and identify small earthquakes before and after the Ludian earthquake using 541 events in the catalogue of the network as templates. The following results are obtained: (1) 991 earthquakes not listed in the catalogue are identified from the continuous waveforms from 33 days before the main earthquake to 5 days after the main earthquake. The complete magnitude of the aftershocks was reduced from 1.8 to 1.3. According to the catalogue, the b value of the aftershocks was 1.04 (+0.18) within 33 days before the main shock, and the b value of the aftershocks gradually increased from 0.5 to 0.9 within 5 days after the earthquake and remained stable. (2) According to the catalogue of the seismic network from 2009 to the occurrence of the main shock, the background b value of the region was 0.93 (+0.04). The b values of regional seismicity before and after the impoundment of Xiluodu Reservoir are close to the background B values, which is not consistent with the b value characteristics of moderate and strong earthquakes induced by typical reservoirs. (3) Through further analysis of the network catalogue, it is not found that there are obvious changes in seismic activity in the study area before and after the impoundment of Xiluodu Reservoir, which is also consistent with the seismic activity in the typical reservoir-induced earthquake area. Second, the Ms5.8 earthquake occurred on April 15, 2015 in Alashan Zuoqi, Inner Mongolia Autonomous Region. It is difficult to judge the seismogenic structure from the source position provided by the network catalogue because of the few earthquake events in the network catalogue and the sparse distribution of fixed stations near the epicenter. In this paper, the missing events before and after the Alxa earthquake are searched and identified by using template matching method with the data of several mobile stations near the epicenter and 55 events in the network catalogue as template events. The seismogenic structure of the earthquake is preliminarily analyzed by combining Hypo2000 and HypoDD. 362 missing events were identified in the continuous waveforms from 10 days before the main earthquake to 10 days after the main earthquake; (2) 55 events in the network catalogue were relocated by Hypo 2000, and the theoretical average errors of the horizontal and vertical directions of the focal positions were 2.50 km and 36.9 km respectively, and the theoretical average travel time residuals were 0.58 s; (3) the cross-correlation technique was used to relocate the 55 events in the network catalogue. After the relocation, the predominant distribution of the epicenter is nearly East-West (the predominant trend of least square fitting is 261.4 degrees), which is basically consistent with the direction of nodal plane II (262 degrees) in the focal mechanism solution given by USGS. According to the focal mechanism obtained by different research institutes and scholars, we think that the seismogenic structure of the Alashan Ms5.8 earthquake in 2015 is a sinistral strike-slip fault with a strike of 261 degrees and a high dip angle.
【學(xué)位授予單位】：中國地震局地球物理研究所
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：P315.5
本文編號：2216778
[Abstract]:Earthquake catalogue is the basic data for confirmation of seismogenic structure and analysis of seismicity. However, due to the interference of strong coda waves, small magnitude of earthquake events, sparse distribution of stations and other reasons, it will cause serious deficiency of earthquake catalogue, thus affecting the reliable analysis of seismicity based on earthquake catalogue. The template matching method based on this method is an effective method to detect missing events under low signal-to-noise ratio and has been widely used. In this paper, template matching method is used to solve the following two problems. First, the Ms6.5 earthquake occurred in Ludian County, Yunnan Province on August 3, 2014. After the Ludian earthquake, the Ludian earthquake is considered to be an earthquake. According to previous studies, the analysis of seismicity before and after moderate earthquakes can provide a certain basis for judging the origin of the main earthquake. However, due to the sparse distribution of fixed stations near the epicenter of the Ludian earthquake and the interference of coda waves after the main earthquake, the earthquake catalogue will be absent. In this paper, a template matching method is used to search and identify small earthquakes before and after the Ludian earthquake using 541 events in the catalogue of the network as templates. The following results are obtained: (1) 991 earthquakes not listed in the catalogue are identified from the continuous waveforms from 33 days before the main earthquake to 5 days after the main earthquake. The complete magnitude of the aftershocks was reduced from 1.8 to 1.3. According to the catalogue, the b value of the aftershocks was 1.04 (+0.18) within 33 days before the main shock, and the b value of the aftershocks gradually increased from 0.5 to 0.9 within 5 days after the earthquake and remained stable. (2) According to the catalogue of the seismic network from 2009 to the occurrence of the main shock, the background b value of the region was 0.93 (+0.04). The b values of regional seismicity before and after the impoundment of Xiluodu Reservoir are close to the background B values, which is not consistent with the b value characteristics of moderate and strong earthquakes induced by typical reservoirs. (3) Through further analysis of the network catalogue, it is not found that there are obvious changes in seismic activity in the study area before and after the impoundment of Xiluodu Reservoir, which is also consistent with the seismic activity in the typical reservoir-induced earthquake area. Second, the Ms5.8 earthquake occurred on April 15, 2015 in Alashan Zuoqi, Inner Mongolia Autonomous Region. It is difficult to judge the seismogenic structure from the source position provided by the network catalogue because of the few earthquake events in the network catalogue and the sparse distribution of fixed stations near the epicenter. In this paper, the missing events before and after the Alxa earthquake are searched and identified by using template matching method with the data of several mobile stations near the epicenter and 55 events in the network catalogue as template events. The seismogenic structure of the earthquake is preliminarily analyzed by combining Hypo2000 and HypoDD. 362 missing events were identified in the continuous waveforms from 10 days before the main earthquake to 10 days after the main earthquake; (2) 55 events in the network catalogue were relocated by Hypo 2000, and the theoretical average errors of the horizontal and vertical directions of the focal positions were 2.50 km and 36.9 km respectively, and the theoretical average travel time residuals were 0.58 s; (3) the cross-correlation technique was used to relocate the 55 events in the network catalogue. After the relocation, the predominant distribution of the epicenter is nearly East-West (the predominant trend of least square fitting is 261.4 degrees), which is basically consistent with the direction of nodal plane II (262 degrees) in the focal mechanism solution given by USGS. According to the focal mechanism obtained by different research institutes and scholars, we think that the seismogenic structure of the Alashan Ms5.8 earthquake in 2015 is a sinistral strike-slip fault with a strike of 261 degrees and a high dip angle.
【學(xué)位授予單位】：中國地震局地球物理研究所
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：P315.5
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