自贡-隆昌地区地震重新定位及P波速度结构研究
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摘要
基于2007年1月～2010年8月自贡地方数字测震台网和流动台站记录的地震观测报告,对自贡-隆昌地区开展了地震精定位和速度结构反演两方面的研究工作,并结合研究区地震活动时间序列及注水井(家33井)的加压数据,探讨了注水区域及邻区地震震源深度分布、P波速度结构特征及其与家33井加压注水的关系。定位结果显示:地震的空间丛集性更加明显,集中分布在自贡(A区)、富顺-隆昌交界(B区)及隆昌(C区)等3个区域。其中距家33井西侧约20km的A区地震呈NNE向长轴展布,震源深度主要分布在5～15km;B、C区域内的地震则沿NW向长轴展布,家33井所在的B区绝大多数地震的震源深度在2～6km,即家33井的注水层位附近,呈现由NW至SE的铲形特征,并逐渐变深;位于家33井东南方向约15km的C区,地震震源深度相对B区较深,优势深度在8～15km。分析认为,A区地震活动与家33井加压注水无关,而B、C区域的地震活动却明显受到加压注水的影响。P波速度结构显示:在3km深的注水层位附近,区域B、A之间形成了1条近NS走向的高、低波速过渡带,B区地壳介质的P波速度明显高于A区,其原因是家33井出现容腔饱和,使该区地下介质具有较高含水饱和度引起的。
Based on earthquake observation report recorded by the Zigong local digital seismic network and mobile stations from January 2007 to August 2010, the earthquake relocation and velocity structure inversion are developed in the Zigong and Longchang area. Taking into account the time series of seismic activities and injection pressure of water injection well (Jia 33 well) in study area, we discuss the focal depth distribution, the characteristics of P-wave velocity structure and relationship with injection pressure of Jia 33 well in and around injection region. The positioning result shows that the earthquake space cluster distributions are more obvious, the earthquakes are concentrated in three cluster regions of Zigong (region A), Fushun-Longchang juncture (region B) and Longchang (region C). Region A is about 20km to the west of Jia 33 well, earthquakes distribute along NNE direction, and the dominant range of focal depth is 5～15km. Earthquakes distribute along NW direction in regions B and C. Region B is where Jia 33 well locates in, the focal depth of most earthquakes are between 2km and 6km, which is near the affusion layer of Jia 33 well. The focal depth presents shovel-shaped distribution characteristic which spreads from NW to SE, and then become gradually deep. Region C is about 15km to the southeast of Jia 33 well. The focal depth in region C is relatively deeper than that in region B. The dominant depth is 8～15km. The seismic activities of region A are independent of injection pressure of Jia 33 well. However the injection pressure of Jia 33 well has obvious regulatory effect on seismic activities of Rgions B and C. The P-wave velocity structure shows that near the affusion layer at the depth of 3km, there is a near NS direction transition zone of high-and-low velocity between regions B and A. P-wave velocity in region B is higher than that in region A. We make the conclusion that the significantly increased P-wave velocity in region B results from the higher water saturation of underground medium by square-cavity saturation of Jia 33 well and it has a correlation with injection pressure of Jia 33 well.
Based on earthquake observation report recorded by the Zigong local digital seismic network and mobile stations from January 2007 to August 2010, the earthquake relocation and velocity structure inversion are developed in the Zigong and Longchang area. Taking into account the time series of seismic activities and injection pressure of water injection well (Jia 33 well) in study area, we discuss the focal depth distribution, the characteristics of P-wave velocity structure and relationship with injection pressure of Jia 33 well in and around injection region. The positioning result shows that the earthquake space cluster distributions are more obvious, the earthquakes are concentrated in three cluster regions of Zigong (region A), Fushun-Longchang juncture (region B) and Longchang (region C). Region A is about 20km to the west of Jia 33 well, earthquakes distribute along NNE direction, and the dominant range of focal depth is 5～15km. Earthquakes distribute along NW direction in regions B and C. Region B is where Jia 33 well locates in, the focal depth of most earthquakes are between 2km and 6km, which is near the affusion layer of Jia 33 well. The focal depth presents shovel-shaped distribution characteristic which spreads from NW to SE, and then become gradually deep. Region C is about 15km to the southeast of Jia 33 well. The focal depth in region C is relatively deeper than that in region B. The dominant depth is 8～15km. The seismic activities of region A are independent of injection pressure of Jia 33 well. However the injection pressure of Jia 33 well has obvious regulatory effect on seismic activities of Rgions B and C. The P-wave velocity structure shows that near the affusion layer at the depth of 3km, there is a near NS direction transition zone of high-and-low velocity between regions B and A. P-wave velocity in region B is higher than that in region A. We make the conclusion that the significantly increased P-wave velocity in region B results from the higher water saturation of underground medium by square-cavity saturation of Jia 33 well and it has a correlation with injection pressure of Jia 33 well.
引文
程式、刘文泰,1992,中国注水诱发地震的又一个实例,地震,(1),63～66。
刁守中,1989,山东角07井注水诱发地震序列的时间分布特征,地震,1,27～31。
刁守中、蒋海昆、徐学炎,1990,山东胜利油田角07井注水地震序列的演化及其机制,地震学报,12(4),399～406。
刁守中、周焕鹏、郭爱香,1987,山东角07井注(漏)水诱发地震——震源参数与地震序列特征,地震地质,9(3),84～89。
刘福田,1984,震源位置和速度结构的联合反演(Ⅰ)——理论和方法,地球物理学报,27(2),167～175。
刘福田、李强、吴华等,1989,用于速度图像重建的层析成像法,地球物理学报,32(1),46～61。
马宏生、张国民、闻学泽等,2008,川滇地区三维P波速度结构反演与构造分析,地球科学—中国地质大学学报,33(5),591～602。
阮祥、程万正、张永久等,2008,四川长宁盐矿井注水诱发地震研究,中国地震,24(3),226～234。
沈文略、杨东全,2003,岩石弹性波速度和饱和度、孔隙流体分布的关系,地球物理学报,46(1),138～142。
施行觉、徐果明、靳平等,1995,岩石的含水饱和度对纵、横波速及衰减影响的实验研究,地球物理学报,38(增刊1),281～287。
王椿镛、Mooney W D、王溪莉等,2002,川滇地区地壳上地幔三维速度结构研究,地震学报,24(1),1～16。
谢礼立,2007,论油气田的地震灾害和防御,油气田地面工程,26(12),1～4。
杨智娴、陈运泰、郑月军等,2003,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,中国科学(D辑),33(增刊1),129～134。
赵珠、张润生,1987,四川地区地壳上地幔速度结构的初步研究,地震学报,9(2),154～166。
朱丽霞、黄世源、魏红梅,2007,荣昌地区注水地震研究,大地测量与地球动力学,27(6),86～90。
Aki K,Lee W H K,1976,Determination of three-dimensional velocity anomalies under a seismic array using P arrival times fromlocal earthquakes(1)A homogeneous initial model,J Geophys Res,81,4381～4399.
Healy J H,Rubey W W,Griggs D T,et al,1968,The Denver earthquakes,Science,161,1301～1310.
Humphreys E,Clayton R W,1988,Adaptation of back projection tomography to seismic travel time problems,J Geophys Res,93,1073～1085.
Inoue H,Fukao Y,Tanabe K,et al,1990,Whole mantle P-wave travel time tomography,Phys Earth Planet Interi,59,294～328.
Kauster G T,Toksoz M N,1974,Velocity and attenuation of seismic wave in two-phase media,Geophysics,39(5),607～618.
Pavlis L G,Booker J R,1980,The mixed discrete-continuous inverse problem:Application to the simultaneous determination ofearthquake hypocenters and velocity structure,J Geophys Res,85,4801～4810.
Segall P.,1989,Earthquakes triggered by fluid extraction,Geology,17(10),942～946.
Spencer C,Gubbins D,1980,Travel time inversion for simultaneous earthquake location and velocity structure determination inlaterally varying media,Geophys J R Astron Soc,63(1),95～116.
Thurber C H,1983,Earthquake locations and three-dimensional crustal structure in the Coyote late area,Central California,JGeophys Res,88,8226～8236.
Waldhauser F,Ellsworth W L,2000,A double difference earthquake location algorithm:method and application to the NorthernHayward Fault,California,Bull Seism Soc Amer,90(6),1353～1368.
Yerkes R F,Castle R O,1976,Seismicity and faulting attributable to fluid extraction,Engineering Geology,10(24),151～167.
Zhao D,Hasegawa A,Horiuchi S,1992,Tomographic imaging of P and S wave velocity structure beneath northeastern Japan,JGeophys Res,97,19909～19928.
刁守中,1989,山东角07井注水诱发地震序列的时间分布特征,地震,1,27～31。
刁守中、蒋海昆、徐学炎,1990,山东胜利油田角07井注水地震序列的演化及其机制,地震学报,12(4),399～406。
刁守中、周焕鹏、郭爱香,1987,山东角07井注(漏)水诱发地震——震源参数与地震序列特征,地震地质,9(3),84～89。
刘福田,1984,震源位置和速度结构的联合反演(Ⅰ)——理论和方法,地球物理学报,27(2),167～175。
刘福田、李强、吴华等,1989,用于速度图像重建的层析成像法,地球物理学报,32(1),46～61。
马宏生、张国民、闻学泽等,2008,川滇地区三维P波速度结构反演与构造分析,地球科学—中国地质大学学报,33(5),591～602。
阮祥、程万正、张永久等,2008,四川长宁盐矿井注水诱发地震研究,中国地震,24(3),226～234。
沈文略、杨东全,2003,岩石弹性波速度和饱和度、孔隙流体分布的关系,地球物理学报,46(1),138～142。
施行觉、徐果明、靳平等,1995,岩石的含水饱和度对纵、横波速及衰减影响的实验研究,地球物理学报,38(增刊1),281～287。
王椿镛、Mooney W D、王溪莉等,2002,川滇地区地壳上地幔三维速度结构研究,地震学报,24(1),1～16。
谢礼立,2007,论油气田的地震灾害和防御,油气田地面工程,26(12),1～4。
杨智娴、陈运泰、郑月军等,2003,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,中国科学(D辑),33(增刊1),129～134。
赵珠、张润生,1987,四川地区地壳上地幔速度结构的初步研究,地震学报,9(2),154～166。
朱丽霞、黄世源、魏红梅,2007,荣昌地区注水地震研究,大地测量与地球动力学,27(6),86～90。
Aki K,Lee W H K,1976,Determination of three-dimensional velocity anomalies under a seismic array using P arrival times fromlocal earthquakes(1)A homogeneous initial model,J Geophys Res,81,4381～4399.
Healy J H,Rubey W W,Griggs D T,et al,1968,The Denver earthquakes,Science,161,1301～1310.
Humphreys E,Clayton R W,1988,Adaptation of back projection tomography to seismic travel time problems,J Geophys Res,93,1073～1085.
Inoue H,Fukao Y,Tanabe K,et al,1990,Whole mantle P-wave travel time tomography,Phys Earth Planet Interi,59,294～328.
Kauster G T,Toksoz M N,1974,Velocity and attenuation of seismic wave in two-phase media,Geophysics,39(5),607～618.
Pavlis L G,Booker J R,1980,The mixed discrete-continuous inverse problem:Application to the simultaneous determination ofearthquake hypocenters and velocity structure,J Geophys Res,85,4801～4810.
Segall P.,1989,Earthquakes triggered by fluid extraction,Geology,17(10),942～946.
Spencer C,Gubbins D,1980,Travel time inversion for simultaneous earthquake location and velocity structure determination inlaterally varying media,Geophys J R Astron Soc,63(1),95～116.
Thurber C H,1983,Earthquake locations and three-dimensional crustal structure in the Coyote late area,Central California,JGeophys Res,88,8226～8236.
Waldhauser F,Ellsworth W L,2000,A double difference earthquake location algorithm:method and application to the NorthernHayward Fault,California,Bull Seism Soc Amer,90(6),1353～1368.
Yerkes R F,Castle R O,1976,Seismicity and faulting attributable to fluid extraction,Engineering Geology,10(24),151～167.
Zhao D,Hasegawa A,Horiuchi S,1992,Tomographic imaging of P and S wave velocity structure beneath northeastern Japan,JGeophys Res,97,19909～19928.
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