【摘要】 利用华北遥测台网和首都圈数字地震台网112个台站记录到的1993—2004年发生在首都圈地区3983次地震的P波绝对到时资料和相对到时资料,采用双差地震层析成像方法联合反演首都圈地区的地震震源参数,给出了2809次地震的重新定位结果.经地震重新定位后,P波绝对走时均方根残差由初始的1.2s降为0.3s,定位精度有了非常显著的提高.重新定位后的地震震中更集中分布在断层带地区,条带状更为清晰.在唐山地区的唐山—大城断裂带,地震主要集中在断裂带内,两侧的地震比较稀少.从重新定位后的震中分布可以看出,研究区域内的地震活动带呈现更明显的北北东向和北西西向的条带状分布,说明这两组方向的断裂最为活跃.用双差地震层析成像方法得到的唐山地区的地震震源位置,沿北东方向剖面在深度上呈现明显的3个小震群的特点,震源最大深度为25km.唐山地区地震重新定位结果的对比性研究表明,双差层析成像方法得到的震源参数的精度高于常规地震层析成像方法和双差法.更多还原

【Abstract】 By taking the full advantage of the up-to-date double-difference (DD) seismic tomography method,the 2809 earthquake hypocenters were relocated to enhance their resolution of horizontal and in-depth directions. These earthquakes were all occurred in the Beijing-Tianjin-Tangshan (BTT) region,and the magnitude range of these events was around M1.7-6.2. Absolute arrival time and differential travel time records of 3983 earthquakes during the period 1993-2004 were adopted. These records were elaborately selected from the 112 seismic stations which are parts of both the Northern China Telemetry Seismic Network (NCTSN) and Capital Digital Seismic Network (CDSN). As a result,the root mean square (RMS) residuals of the earthquake hypocenters were greatly reduced from 1.2 s to 0.3 s. The relocated hypocenters of earthquakes showed an even clear configuration along the major faults than that of before relocating. Moreover,some of them were concentrated along with the major faults in a shape of alignment in some particular regions,such as the Tangshan-Dacheng fault zone in Tangshan region. In this region,all the events were mainly located in the fault zones,and only few of them were exceptional. From the horizontal distribution profile of the relocated earthquake hypocenters,the seismicities appeared clearly as two "belt-shape" characteristics both in NNE and WNW directions. It revealed that these two regions are currently seismic active nowadays. From the north-east (NE) cross sectional profile of this region,the relocated hypocenters of earthquakes were clustered as three typical groups,and the maximum focal depth of these earthquakes is 25 km. We also compared our relocation result with those from the standard tomography method and DD relocation method,which used the absolute travel-time catalog data and relative travel-time catalog data,respectively. The comparisons confirmed that our DD tomography could produce much higher resolution hypocenter parameters than that from the standard tomography and DD relocation methods.更多还原