Partitioning of convergence in Northwest Sub-Himalaya: estimation of late Quaternary uplift and convergence rates across the Kangra reentrant, North India
Partitioning of convergence in Northwest Sub-Himalaya: estimation of late Quaternary uplift and convergence rates across the Kangra reentrant, North India
复制标题
西北次喜马拉雅地区的辐合划分：印度北部坎格拉折返地区晚第四纪隆升和辐合速率的估计
DOI：
10.1007/s00531-014-1016-7
复制
发表时间：
2014
影响因子：
2.3
通讯作者：
Ajit Singh
中科院分区：
文献类型：
--
作者：
V. C. Thakur;M. Joshi;D. Sahoo;N. Suresh;R. Jayangondapermal;Ajit Singh
康格拉折返带构成了喜马拉雅山西北部前陆盆地新生代地层宽约 80 公里的褶皱冲断带。早期的工作人员估计，通过主边界逆冲断层和喜马拉雅额冲断层之间的平衡横截面，长期总缩短率为 14 ± 2 毫米/年。地质估计的滑移率与 GPS 得出的滑移率（14 ± 1 毫米/年）几乎一致。折返区亚喜马拉雅褶皱逆冲带4-8公里深度内发育有活动断层。对逆冲断层上方废弃的河流阶地和扇的地层表面进行年代测定，计算隆起（基岩切割）率。逆冲断层的倾角是根据现有的地震（深度）剖面在现场测量的。根据获得的数据，估算了贾瓦拉穆希逆冲断层（JT）、索安逆冲断层（ST）和喜马拉雅锋面逆断层（HFT）的晚第四纪缩短率。在 32-30ka 期间，JT 的缩短率为 3.5-4.2 毫米/年。 ST 的缩短率为 3.0 毫米/年，持续 29 ka。根据 HFT 估计，在 42ka 期间，相应的缩短率和滑移率分别为 6.0 和 6.9 毫米/年。在 Janauri 背斜的反冲断层上，同一时期的缩短率和滑移率分别为 2.0 和 2.2 毫米/年。结果表明，缩短主要分布在 JT 和 HFT 之间 50 公里宽的区域。重新激活的 HFT 记录的大地震和特大地震的地表破裂的出现意味着破裂宽度≥100 公里。 1905 年的坎格拉地震和 2005 年的克什米尔地震等大地震的破裂仍然仅限于腹地。目前的研究表明，大地震可能发生在锁定线和活动逆冲断层之间。
The Kangra reentrant constitutes a ~ 80-km-wide zone of fold-thrust belt made of Cenozoic strata of the foreland basin in NW Sub-Himalaya. Earlier workers estimated the total long-term shortening rate of 14 ± 2 mm/year by balanced cross-section between the Main Boundary Thrust and the Himalayan Frontal Thrust. Geologically estimated rate is nearly consistent with the GPS-derived slip rate of 14 ± 1 mm/year. There are active faults developed within 4–8 km depth of the Sub-Himalayan fold-thrust belt of the reentrant. Dating the strath surfaces of the abandoned fluvial terraces and fans above the thrust faults, the uplift (bedrock incision) rates are computed. The dips of thrust faults are measured in field and from available seismic (depth) profiles. From the acquired data, late Quaternary shortening rates on the Jawalamukhi Thrust (JT), the Soan Thrust (ST) and the Himalayan Frontal Thrust (HFT) are estimated. The shortening rates on the JT are 3.5–4.2 mm/year over a period 32–30 ka. The ST yields a shortening rate of 3.0 mm/year for 29 ka. The corresponding shortening and slip rates estimated on the HFT are 6.0 and 6.9 mm/year during a period 42 ka. On the back thrust of Janauri Anticline, the shortening and slip rates are 2.0 and 2.2 mm/year, respectively, for the same period. The results constrained the shortening to be distributed largely across a 50-km-wide zone between the JT and the HFT. The emergence of surface rupture of a great and mega earthquakes recorded on the reactivated HFT implies ≥100 km width of the rupture. The ruptures of large earthquakes, like the 1905 Kangra and 2005 Kashmir, remained restricted to the hinterland. The present study indicates that the high magnitude earthquakes can occur between the locking line and the active thrusts.