Observed travel-time curves by stacking records from Lanzhou small aperture seismic array
-
摘要: 使用兰州小孔径地震台阵记录的近10年地震观测垂直分量波形数据， 采用长、 短时间平均数比值方法(STA/LTA)叠加出适用于青藏高原东北缘地区的观测走时曲线. 结果表明， 兰州小孔径地震台阵独特的地理位置， 基本上能够记录到不同震中距(0—180°)和不同方位的地震事件； 使用不同频率滤波处理之后的地震数据记录叠加出相应的观测走时曲线， 从观测走时曲线中可以识别出不同体波震相(P， PKIKP， PKP， PP， PPP， PcP， ScP， S， SS等)的到时及其观测走时曲线特征. 这对识别地震各种震相， 认识和研究地球内部精细结构等具有非常重要的科学意义.Abstract: Based on the past 10 years vertical observational waveforms recorded by Lanzhou small aperture seismic array, which is located at the northeastern margin of the Tibetan Plateau, the observed travel-time curves are obtained by using STA/LTA technique. The results show that Lanzhou seismic array can record events with different epicentral distances between 0—180° and with different azimuths due to its particular location. By stacking the seismic records filtered with different frequencies, we can get corresponding observed travel-time curves so as to identify different body wave phases, such as P, PKIKP, PKP, PP, PPP, PcP, ScP, S, SS, and to study the characteristics of travel-time curves. It is of scientific significance to identify various seismic phases and further study fine structure of the Earth’s interior.
-
-
![]()
图 1 兰州小孔径地震台阵示意图.三角形表示台阵各子台的位置
Figure 1. Sketch of Lanzhou small aperture seismic array, where the triangle denotes station and the rectangle denotes the observatory
![]()
图 2 地震震中分布图. 三角形表示台阵的位置， 小圆点表示震中
Figure 2. Epicentral distribution used in this study, where the triangle represents the Lanzhou seismic array and the dots are epicenters
![]()
图 3 不同震中距与地震数目分布图
Figure 3. Histogram of number of events in 0.5° epicentral distance bin for the earthquakes used in this study
![]()
图 4 (a)兰州小孔径台阵10 s低通滤波之后的记录(2010年7月4日日本本州东海岸附近地震，震中距为30.6°，MS6.3). STACK为9个子台的平均叠加结果;(b)STACK作STA/LTA的计算结果;(c)该地震事件0.5°震中距范围内所有地震事件作STA/LTA的叠加平均结果
Figure 4. (a) Records of an earthquake (MS6.3, epicentral distance 30.6°, 2010-07-04) in Coast of Honshu, Japan, on nine stations of Lanzhou seismic array, which were filtered by 10s low-pass filter; (b) The computed STA/LTA for the STACK trace; (c) The average STA/LTA resulting from all traces within a 0.5° distance range
![]()
图 5 垂直分量2 s高通滤波叠加的观测走时曲线(a)和可识别震相IASP91模型理论走时曲线(b)
Figure 5. Vertical stacking of travel-time curves after a 2 s high-pass filter was applied to each trace (a) and travel times of the identifiable seismic phases based on the IASP91 velocity model (b)
![]()
图 6 垂直分量6 s高通滤波叠加的观测走时曲线(a)和可识别震相IASP91模型理论走时曲线(b)
Figure 6. Vertical stacking of travel-time curves after a 6 s high-pass filter was applied to each trace (a) and travel times of the identifiable seismic phases based on the IASP91 velocity model (b)
![]()
图 7 垂直分量10 s低通滤波叠加的观测走时曲线(a)和可识别震相IASP91模型理论走时曲线(b)
Figure 7. Vertical stacking of travel-time curves after a 10 s low-pass filter was applied to each trace (a) and travel times of the identifiable seismic phases based on the IASP91 velocity model (b)
![]()
图 8 垂直分量30 s低通滤波叠加的观测走时曲线(a)和可识别震相IASP91模型理论走时曲线(b)
Figure 8. Vertical stacking of travel-time curves after a 30 s low-pass filter was applied to each trace (a) and travel times of the identifiable seismic phases based on the IASP91 velocity model (b)
![]()
图 9 垂直分量100 s低通滤波叠加的观测走时曲线(a)和可识别震相IASP91模型理论走时曲线(b)
Figure 9. Vertical stacking of travel-time curves after a 100 s low-pass filter was applied to each trace (a) and travel times of the identifiable seismic phases based on the IASP91 velocity model (b)
![]()
图 10 垂直分量5种不同滤波综合叠加的观测走时曲线(a)和可识别震相IASP91模型理论走时曲线(b)
Figure 10. Vertical stacking result after five different filters were applied to each trace (a) and travel times calculated for the IASP91 velocity model showing the identifiable seismic phases (b)
![]()
图 11 兰州小孔径地震台阵极远震记录(2003年 1月22日墨西哥地震， 震中距119.5°， MS7.5). STACK为台阵9个子台叠加记录， 记录中可以识别Pdiff, PKIKP, PP, PPP等震相
Figure 11. The far most earthquake recordings of a MS=7.5 event that occurred in Mexico on January 22, 2003, on Lanzhou seismic array. This event is located 119.5° away. These traces have been low-pass filtered at 10 s and the arrivals of a few phases (Pdiff， PKIKP， PP, PPP) are identified
![]()
图 12 (a) 台湾MS5.7地震(东南方向)和新疆MS6.0地震(西北方向)相同震中距(19.2°)观测波形对比； (b) 相同深度(30 km±3 km)、 不同方位(75°和200°)、 相近震中距(30.5°和31.0°)多次地震叠加的P波观测走时与理论走时对比； (c)相同深度(均为10 km)、 不同方位(136°和250°)、 相同震中距(49.0°)多次地震叠加的P波观测走时与理论走时的对比． 图b， c中垂直黑线为叠加的P波观测走时， 蓝线为理论走时
Figure 12. (a) Comparison of earthquake waveforms with the same epicentral distance (19.2°) between Taiwan MS5.7 (southeast) and Xinjiang MS6.0 (northwest) earthquakes. (b) Comparison of observed travel times with theoretical ones of the multiple earthquakes stacking of P-wave traces. The earthquakes have the same depth (30 km±3 km), the different back azimuth (75° and 200°) and the nearly similar distance (30.5° and 31.0°). (c) Comparison of observed P-wave travel times with theoretical ones of the multiple earthquakes stacking. The earthquakes have the same focal depth (10 km), the different back azimuth (136° and 250°) and the same distance (49.0°). In Figs.2b, c, the black vertical line is the observed stacked travel time for P wave and the blue one is the corresponding theoretical travel time
表 1 不同滤波和STA/LTA参数表
Table 1 Filtering and STA/LTA parameters
滤波 STA/s LTA/s 2 s高通 1 9 6 s高通 2 20 10 s低通 3 30 30 s低通 5 45 100 s低通 10 90 
下载: 导出CSV
-
秦满忠, 张元生, 沈旭章, 魏从信. 2012. 小孔径台阵垂直分量P波接收函数研究及应用[J]. 地震学报, 34 (1): 44-51. Qin M Z, Zhang Y S, Shen X Z, Wei C X. 2012. A study on vertical-component P-wave receiver function of small-aperture seismic array and its application[J]. Acta Seismologica Sinica, 34 (1): 44-51 (in Chinese)
沈旭章, 周蕙兰. 2009. 用PKIKP的前驱震相探测青藏高原东部地幔底部的散射体[J]. 科学通报, 54 (24): 3844-3851. Shen X Z, Zhou H L. 2009. Locating seismic scatterers at the base of the mantle beneath eastern Tibet with PKIKP precursors[J]. Chinese Sci Bull, 54 (24): 3844-3851 (in Chinese)
沈旭章, 梅秀苹, 张淑珍, 秦满忠. 2010. 兰州台阵响应函数及不同方位地震事件FK分析结果[J]. 西北地震学报, 32 (1): 59-64. Shen X Z, Mei X P, Zhang S Z, Qin M Z. 2010. The array response function of Lanzhou seismic array and results of FK analysis for small earthquakes in different azimuths[J]. Northwestern Seismological Journal, 32 (1): 59-64 (in Chinese).
周元泽, 王卓君. 2011. 伊豆-小笠原和汤加地区中地幔多层速度结构差异性研究[J]. 中国科学: D辑, 41 (7): 936-944 Zhou Y Z, Wang Z J. 2011. On the difference of mid-mantle multiple velocity structure beneath Izu-Bonin and Tonga areas[J]. Science in China: Series D, 41 (7): 936-944 (in Chinese)
中国地震局监测预报司. 2007. 地震学与地震观测[M]. 北京: 地震出版社: 172 Department of Earthquake Monitoring and Predition, China Earthquake Administration. 2007. Seismology and Earthquake Observation[M]. Beijing: Seismological Press: 172 (in Chinese)
Astiz L, Earle P, Shearer P. 1996. Global stacking of broadband seismograms[J]. Seismol Res Lett, 67 (4): 8-18.
Earle P S, Shearer P M. 1994. Characterization of global seismograms using an automatic-picking algorithm[J]. Bull Seismol Soc Am, 84 (2): 366-376.
Gaia S, Lapo B, Antonio P. 2006. Global seismic tomography and modern parallel computers[J]. Annals of Geophysics, 49 (4/5): 977-986
Rost S, Thomas C. 2002. Array seismology: Methods and applications[J]. Rev Geophys, 40 (3): 2-1-2-27. doi:10.1029/2000RG000100
Rost S, Thorne M S, Garnero E J. 2006. Imaging global seismic phase arrivals by stacking array processed short-period data[J]. Seismol Res Lett , 77 (6): 697-707
Shearer P M. 1991. Imaging global body wave phases by stacking long-period seismograms[J]. J Geophys Res, 96 (B12): 20353-20364
Shearer P M. 1994. Imaging Earth's seismic response at long periods[J]. Eos Trans AGU, 75 (39): 449-452
Shen X, Ritter J R R. 2010. Small-scale heterogeneities below the Lanzhou CTBTO seismic array, from seismic wavefield fluctuations[J]. J Seismol, 14 (3): 481-493
Walck M C, Clayton R W. 1984. Analysis of upper mantle structure using wave field continuation of P waves[J]. Bull Seismol Soc Am, 74 (5): 1703-1719
计量
- 文章访问数: 626
- HTML全文浏览量: 234
- PDF下载量: 20
