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721.
Syn-collisional transform faulting of the Tan-Lu fault zone,East China 总被引:21,自引:0,他引:21
Guang Zhu Guo Sheng Liu Man Lan Niu Cheng Long Xie Yong Sheng Wang Biwei Xiang 《International Journal of Earth Sciences》2009,98(1):135-155
Origin of the continental-scale Tan-Lu fault zone (TLFZ), East China, remains controversial. About 550 km sinistral offset
of the Dabie orogenic belt (DOB) and Sulu orogenic belt (SOB) is shown along the NE-NNE-striking TLFZ. Syn-collisional, sinistral
ductile shear belts in the TLFZ have been identified. Thirteen phengite bulk separates from the mylonites were dated by the
40Ar/39Ar method. They gave cooling ages of the 198–181 Ma for the shear belts along the eastern margin of the DOB and 221–210 Ma
from the western margin of the SOB. Distribution of the foreland basin deposits suggests that sinistral offset of the DOB
and SOB by the TLFZ took place prior to deposition of the Upper Triassic strata. The marginal structures around the DOB and
SOB support syn-collisional faulting, and indicate anticlockwise rotation of the DOB during the displacement. The folding
and thrust faulting related to crustal subduction, coeval with the Tan-Lu faulting, is older than the foreland basin deposition
related to the orogenic exhumation. Several lines of evidence demonstrate that the TLFZ was developed as a syn-collisional
transform fault during latest Middle to earliest Late Triassic time when the DOB and SOB experienced crustal subduction of
the South China Block (SCB). Eastward increase of the crustal subduction rates is believed to be responsible for the sinistral
transform faulting. 相似文献
722.
723.
孟津县一次龙卷天气过程分析 总被引:1,自引:0,他引:1
利用灾后调查资料、常规观测资料及三门峡市多普勒雷达资料,分析2007年7月发生在洛阳市孟津县的严重风灾,结果表明:这是孟津县首次在非观测区确认的龙卷灾害;该龙卷为非超级单体龙卷,在反射率因子图上几乎没有任何明显特征,而在风暴径向速度图上呈现为较明显的小尺度涡旋特征;具有显著的低层辐合高层辐散的特征;低的抬升凝结高度和低层明显的垂直风切变及合适的对流有效位能、对流抑制能量是产生龙卷适宜的环境条件;在高低空深厚的槽前西南急流引导下,来自洛阳市西部的弱回波快速东北偏北移到孟津境内强烈快速发展,形成的强回波遇到近地面层的辐合线在弱冷空气的触发下诱发龙卷暴发. 相似文献
724.
Xiucai Li Manlan Niu Chris Yakymchuk Qi Wu Changlei Fu 《Journal of Metamorphic Geology》2019,37(4):479-508
The early Palaeozoic South Qilian–North Qaidam orogenic belt in northwestern China records a nearly complete history of early‐stage long‐lived oceanic subduction–accretion followed by late‐stage continental collision. Most previous studies have focused on low dT/dP metamorphism (HP–UHP) in this belt whereas the paired high dT/dP belt in the hinterland has received little attention. In this contribution, phase equilibrium modelling is combined with zircon petrochronology to determine the P–T–t evolution of granulites in the North Wulan gneiss complex in the high dT/dP hinterland of the South Qilian–North Qaidam orogen. Granulites record a clockwise P–T path with near‐peak temperatures of ~800–900°C at 5.5–7 kbar. Peak metamorphism was followed by high‐T decompression. Zircon petrochronology reveals protracted zircon growth from c. 474 to 446 Ma during the high‐T portion of the P–T path. High dT/dP metamorphism in the North Wulan gneiss complex was likely the result of heat transfer from the underlying hot asthenosphere and minor coeval magmatism in an arc–back‐arc system during slab retreat and roll‐back of the South Qilian oceanic plate. Broadly contemporaneous but slightly younger HP–UHP metamorphism in the foreland of the South Qilian–North Qaidam orogenic belt indicates that the region records an early Palaeozoic paired metamorphic belt. This early Palaeozoic paired metamorphic belt provides a detailed example of dual thermal regimes in a modern‐style orogenic system that can be applied to understanding the time‐scales and P–T conditions of high dT/dP metamorphism that accompany subduction in Phanerozoic and Precambrian orogenic belts. 相似文献
725.
726.
The recently built China Digital Seismic Network consists of the China National Digital Seismic Network (CNDSN),31 regional seismic networks and several small aperture arrays with more than 1 000 stations including 850+ broadband stations.It forms a gigantic seismic array that provides an unprecedented opportunity to study the Earth's deep interior besides its routine task of seismic monitoring.Many modern seismic studies rely on rotation of vertical and horizontal components in order to separate different ... 相似文献
727.
Elizabeth Vanacore 《地震学报(英文版)》2011,(1):87-99
SKS and SKKS waveforms from 16 events occurring between 2003 and 2005 in the Tonga Trench that were recorded by the BOLIVAR array are analyzed to determine the structure of the D layer beneath the Galapagos Islands.248 differential travel-time residuals of SKKS-SKS are measured and reveal a region of positive residuals of differential travel times in the northeast portion of the sampled region.Analyzing correlation statistics between the measured SKKS-SKS residuals and the observed absolute travel time dela... 相似文献
728.
Qifu Chen Le Li Fenglin Niu Jinrong Su Institute of Earthquake Science China Earthquake Administration Beijing China 《地震学报(英文版)》2011,(1):101-106
Repeating microearthquakes were identified along the edge of the rupture area of the 2008 MW7.9 Wenchuan earthquake.Slip rates at depths derived from seismic moments and recurrence intervals are found to be systematically larger than those observed at surface.This large deep slip rate may explain the odds about the occurrence of this unanticipated event.Our observations here suggested that seismic hazard could be underestimated if surface measurements alone are employed. 相似文献
729.
730.