川滇地区中小震重新定位与速度结构的联合反演研究

摘要/Abstract

摘要： 通过震源与速度结构联合反演, 利用2000年4月至2006年3月云南和四川区域地震台网给出的P波初至走时资料, 确定了川滇地区的三维速度结构, 同时获得了川滇地区6642次中小地震的重新定位结果。结果表明: ① 川滇地区地震震源平均深度随震级增大而加深的特征明显, 地震震级越大, 震源深度越深, 但震源下界不超过25 km; ② 在瑞丽-龙陵、丽江-小金河以及龙门山等断裂带以西地区, 震源深度偏浅, 大多在15 km以上, 15 km深度以下地震稀少; ③ 川滇地区中小地震分布具有与强震相同的地壳深部介质背景, 震源大多分布于正、负异常过渡区的速度相对较高一侧, 而其下方主要为低速异常分布。

关键词: 川滇地区, 联合反演, 重新定位, 速度结构

Abstract: Using the data of P wave travel time recorded at Yunnan and Sichuan local networks from April 2000 to March 2006, we implemented a simultaneous inversion of earthquake relocation and velocity structure, and got the new location of 6642 small and medium earthquakes in Sichuan-Yunnan region. The results show that: ① There is an obvious relationship between the focal depth and the magnitude. The bigger the magnitude, the deeper the focal depth, but all the focal depths values are shallower than 25 km; ② There are few earthquakes occurred at the depth deeper than 15 km in regions west of Ruili-Longling, Lijiang-Xiaojinhe and Longmenshan faults; ③ Small and medium earthquakes have the similar seismogenic background as large earthquakes. Along the transitional zone of high velocity and low velocity, most of the earthquakes happened at the higher velocity side, and usually there is a low velocity zone below where earthquakes happened.

Key words: Sichuan-Yunnan area, Simultaneous inversion, Earthquake relocation, Velocity structure

中图分类号:

P315.7

马宏生, 张国民, 周龙泉, 刘杰, 邵志刚, 夏红. 川滇地区中小震重新定位与速度结构的联合反演研究[J]. 地震, 2008, 28(2): 29-38.

MA Hong-sheng, ZHANG Guo-min, ZHOU Long-quan, LIU Jie, SHAO Zhi-gang, XIA Hong. Simultaneous inversion of small earthquakerelocation and velocity structure in Sichuan-Yunnan area[J]. EARTHQUAKE, 2008, 28(2): 29-38.

参考文献

[1] Pavlis L G. Appraising earthquake hypocenter location errors: a complete, practical approach for single-event locations[J]. Bull Seism Soc Am, 1986, 76: 1699-1717.
[2] Gomberg J S, Shedlock K M, Roecker S W. The effect of S-wave arrival times on the accuracy of hypocenter estimation[J]. Bull Seism Soc Am, 1990, 80: 1605-1628.
[3] Geiger L. Probability method for the determination of earthquake epicenters from arrival time only[J]. Bull St Louis Univ, 1912, 8: 60-71.
[4] Poupinet G, Ellsworth W L, Fréchet J. Monitoring velocity variations in the crust using earthquake doublets: an application to the Calaveras fault, California[J]. J Geophys Res, 1984, 89: 5719-5731.
[5] Got J L, Fréchet J, Klein F W. Deep fault plane geometry inferred from multiplet relative relocation beneath the south flank of Kilauea[J]. J Geophys Res, 1994, 99: 15375-15386.
[6] Spence W. Relative epicenter determination using P-wave arrival-time differences[J]. Bull Seism Soc Am, 1980, 70: 171-183.
[7] Ito A. High resolution relative hypocenters of similar earthquakes by cross-spectral analysis method[J]. J Phys Earth 1985, 33: 279-294.
[8] Frémont M J, Malone S D. High precision Relative locations of earthquakes at Mount St. Helens, Washington[J]. J Geophys Res, 1987, 92: 10223-10236.
[9] 周仕勇, 许忠淮, 韩京, 等. 主地震定位方法分析及1997年新疆伽师震群高精度定位[J]. 地震学报, 1999, 21(3): 258-265.
[10] Waldhauser F, Ellsworth W L. A double-difference earthquake location algorithm: Method and Application to the Northern Hayward fault[J]. Bull Seism Soc Am, 2000, 90(6): 1353-1368.
[11] 杨智娴, 陈运泰, 郑月军, 等. 双差地震定位法在我国中西部地区地震精确定位中的应用[J]. 中国科学(D辑): 2003, 33(增刊): 129-134.
[12] 朱艾斓, 徐锡伟, 周永胜, 等. 川西地区小震重新定位及其活动构造意义[J]. 地球物理学报, 2005, 48(3): 629-636.
[13] Aki K, Lee W H K. Determination of three-dimensional velocity anomalies under a seismic array using P arrival times from local earthquakes. 1. A homogeneous initial model[J]. J Geophys Res, 1976, 81: 4381-4399.
[14] Thurber C H. Earthquake locations and three-dimensional crustal structure in the Coyote late area, Central California[J]. J Geophys Res, 1983, 88: 8226-8236.
[15] 刘福田, 李强, 吴华, 等. 用于速度图像重建的层析成像法[J]. 地球物理学报, 1989, 32(1): 46-61.
[16] Zhao D, Hasegawa A, Horiuchi S. Tomographic imaging of P and S wave velocity structure beneath northeastern Japan[J]. J Geophys Res, 1992, 97: 19909-19928.
[17] Smith G P, Ekstrom G. Improve teleseismic event location using a three-dimensional earth model[J]. Bull Seism Soc Am, 1996, 86: 788-796.
[18] Crosson R S. Crustal structure modeling of earthquake data, 1, Simultaneous least squares estimation of hypocenter and velocity parameters[J]. J Geophys Res, 1976, 81: 3036-3046.
[19] Pavlis L G, Booker J R. The mixed discrete-continuous inverse problem: Application to the simultaneous determination of earthquake hypocenters and velocity structure[J]. J Geophys Res, 1980, 85: 4801-4810.
[20] Spencer C, Gubbins D. Travel time inversion for simultaneous earthquake location and velocity structure determination in laterally varying media[J]. Geophys J R Astron Soc, 1980, 63(1): 95-116.
[21] 刘福田. 震源位置和速度结构的联合反演(Ⅰ)理论和方法[J]. 地球物理学报, 1984, 27(2): 167-175.
[22] Michael A J. Effects of three-dimensional velocity structure on the seismicity of the 1984 Morgan Hill, California, aftershock sequence[J]. Bull Seism Soc Am, 1988, 78: 1199-1221.
[23] Kissling E, Ellsworth W L, Eberhard-Phillips D, et al. Initial reference models in local earthquake tomography[J]. J Geophys Res, 1994, 99: 19635-19646.
[24] 李坪, 汪良谋. 云南川西地区地震地质基本特征的探讨[J]. 地质科学, 1975, (4): 308-325.
[25] 阚荣举, 张四昌, 晏风桐, 等. 我国西南地区现代构造应力场与现代构造活动特征的探讨[J]. 地球物理学报, 1977, 20(2): 96-109.
[26] 马杏垣主编. 中国岩石圈动力学图集[M]. 北京: 地图出版社, 1989.
[27] 丁国瑜. 活动亚板块、构造块体相对运动[A].丁国瑜主编. 中国岩石圈动力学概论[C]. 北京: 地震出版社, 1991. 142-153.
[28] 邓起东, 张培震, 冉勇康, 等. 中国活动构造基本特征[J]. 中国科学(D辑), 2002, 32(12): 1020-1030.
[29] 张培震, 邓起东, 张国民, 等. 中国大陆的强震活动与活动地块[J]. 中国科学(D辑), 2003, 33(增刊): 12-20.
[30] 徐锡伟, 闻学泽, 郑荣章, 等. 川滇地区活动块体最新构造变动样式及其动力来源[J]. 中国科学(D辑), 2003, 33(增刊): 151-162.
[31] 刘建华, 刘福田, 吴华, 等. 中国南北带地壳和上地幔的三维速度结构[J]. 地球物理学报, 1989, 32(2): 143-151.
[32] 陈培善, 刘福田, 李强, 等. 云南地区速度结构的横向不均匀性[J]. 中国科学(B), 1990, (4): 431-438.
[33] 王椿镛, 王溪莉, 颜其中. 昆明地震台网下方的三维速度结构[J]. 地震学报, 1994, 16(2): 167-175.
[34] 王椿镛, Mooney W D, 王溪莉, 等. 川滇地区地壳上地幔三维速度结构研究[J]. 地震学报, 2002, 24(1): 1-16.
[35] Huang J, Zhao D, Zheng S. Lithosphere structure and its relationship to seismic and volcanic activity in southwest China[J]. J Geophys Res, 2002, 107(B10), doi: 10.1029/2000JB000137.
[36] 何正勤, 叶太兰, 苏伟. 云南地区地壳中上部横波速度结构研究[J]. 地球物理学报, 2004, 47(5): 838-844.
[37] 张国民, 汪素云, 李丽, 等. 中国大陆地震震源深度及其构造含义[J]. 科学通报, 2002, 47(9): 663-668.
[38] 熊熊, 许厚泽, 滕吉文. 青藏高原物质东流力学背景探讨[J]. 地壳形变与地震, 2001, 21(2): 1-7.
[39] Humphreys E, Clayton R W. Adaptation of back projection tomography to seismic travel time problems[J]. J Geophys Res, 1988, 93: 1073-1085.
[40] Inoue H, Fukao Y, Tanabe K, et al. Whole mantle P-wave travel time tomography[J]. Phys Earth Planet Inter, 1990, 59: 294-328.
[41] 金安蜀, 刘福田, 孙永智. 北京地区地壳和上地幔的三维P波速度结构[J]. 地球物理学报, 1980, 23(2): 172-182.
[42] 朱露培, 曾融生, 刘福田. 京津唐张地区地壳上地幔三维 P波速度结构[J]. 地球物理学报, 1990, 33(3): 267-277.
[43] 齐诚, 赵大鹏, 陈颙, 等. 首都圈地区地壳P波和S波三维速度结构及其与大地震的关系[J]. 地球物理学报, 2006, 49(3): 805-815.
[44] 周龙泉, 刘杰, 陈晓非, 等. 2003年大姚6.2、 6.1级地震序列震源位置及震源区速度结构的联合反演[J]. 地震, 2008, 28(3): (待刊).
[45] 刘福田, 曲克信, 吴华, 等. 华北地区的地震层析成像[J]. 地球物理学报, 1986, 29(5): 442-449.
[46] 黄金莉, 赵大鹏, 郑斯华. 川滇活动构造区地震层析成像[J]. 地球物理学报, 2001, 44(增刊): 127-135.
[47] Wang Chunyong, Chan W, Winston, et al. Three-dimensional velocity structure of crust and upper mantle in southwestern China and its tectonic implications[J]. J Geophys Res, 2003, 108(9): 2442.
[48] Zhao D, Kanamori H, Wiens D. State of stress before and after the 1994 Northridge earthquake[J]. Geophys Res Lett, 1997, 24: 519-522.
[49] Kayal J R, Zhao D, Mishra O P et al. The 2001 Bhuj earthquake: Tomographic evidence for fluids at the hypocenter and its implications for rupture nucleation[J]. Geophys Res Lett, 2002, 29(10): 1029/2002GL015177.
[50] Mishra O P, Zhao D. Crack density, saturation rate and porosity at the 2001 Bhuj, India, earthquake hypocenter: A fluid driven earthquake?[J]. Earth Planet Sci Lett, 2003, 212: 393-405.
[51] Zhao D, Mishra O, Sanda R. Influence of fluids and magma on earthquakes: seismological evidence[J]. Phys Earth Planet Inter, 2002, 132: 249-267.