利用GPS资料和块体模型对巴颜喀拉块体划分合理性的初步探究和构造意义  

Preliminary Study on the Division of the Bayan Har Block Using GPS Data and a Block Model and the Tectonic Implications of the Division

作　　者：姚生海[1] 程佳 姚琪[3] 张加庆[1] YAO Shenghai;CHENG Jia;YAO Qi;ZHANG Jiaqing(Qinghai Earthquake Agency,Xining 810010,Xiningi,China;Institute of Crustal Dynamics,CEA,Beijing 100085,China;China Earthquake Network Center,China Earthquake Agency,Beijing 100045,China)

机构地区：[1]青海省地震局,青海西宁810010 [2]中国地震局地壳应力研究所,北京100085 [3]中国地震台网中心,北京100045

出　　处：《地震工程学报》2018年第5期1042-1051,共10页China Earthquake Engineering Journal

基　　金：国家自然科学基金(41404043);中国地震局星火计划(XH18051)

摘　　要：利用GPS速度场资料和块体模型分别建立巴颜喀拉块体的两种块体模型并反演其滑动速率,模型Ⅰ中巴颜喀拉块体包括东昆仑断裂带西段地区,模型Ⅱ中则不包括该地区。GPS反演结果显示,模型Ⅱ较模型Ⅰ合理,这一合理性包括了模型Ⅱ中阿尔金断裂带西南尾端较大的拉张速率与较小的走滑速率;模型Ⅱ中东昆仑断裂带中段滑动速率约为8~9mm/a,与10mm/a的研究结果更为接近;模型Ⅰ中东昆仑断裂带西段具有较大的走滑速率与挤压速率,也与现今地震活动与震源机制相矛盾;但模型Ⅱ中巴颜喀拉块体在玛尔盖茶卡断裂带滑动速率较大,认为可能与风火山断裂带处的滑动速率较小有关,因此进一步舍去该断裂带,建立新的模型Ⅲ,所得结果与各断裂研究结果较为近似。巴颜喀拉块体南边界风火山断裂带目前活动较弱,下地壳软弱物质可能已经进入巴颜喀拉块体部分地区;风火山断裂带向东经玉树—甘孜—鲜水河断裂带,在下地壳流动与重力滑塌作用下左旋速率逐渐增大。We first establish two kinematic models of the Bayan Har block and inverse the slip rate of the boundary faults using a block model and GPS data.Model I includes the west segment of the East Kunlun fault and its surrounding areas,while Model II does not include this region.The inversion results show that model II is more consistent with the reported survey results.The differences between the two models are as follows:(1)In model II,the extension rate is higher and strike slip rate is smaller on the southwestern section of the Altyn Tagh fault;this observation is more consistent with the regional characteristics of the area.(2)In model II,the sinistral slip rate of the middle part of the East Kunlun fault is about 8 mm/a,which is closer to the reported results of about 10 mm/a.The slip rate is about 7 mm/a in model I.(3)Model I has a larger strike slip rate on the western segment of the East Kunlun fault;this result is not in agreement with the low seismicity and focal mechanism observed in the area.However,in model II,the Maergaichaka fault has a high sinistral slip rate,which may be caused by the small slip rate on the Fenghuoshan fault.Hence,we omit the Fenghuoshan fault to obtain a simplified model II and refer to it as model III.The inversion results for model III are more consistent with the reported results.It is known that the middle section of the East Kunlun fault and the Maergaichaka fault are not connected,but the two faults are continuous with regard to the transfer of the crustal material with the corresponding slip rates.Owing to the low slip rate of the Fenghuoshan fault on the southern boundary of the Bayan Har block,we believe that the weak material in the lower crust may have entered to part of the Bayan Har block.

关 键 词：巴颜喀拉块体 东昆仑断裂带 GPS 块体模型 滑动速率 

分 类 号：P315.2[天文地球—地震学] P228.4[天文地球—固体地球物理学]