我所2016年发表论文欣赏-第十六期

地球所研究生会 · 公众号 · · 2017-04-10 11:02

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题目

Characteristics of Focal Mechanisms and the Stress Field in the Southeastern Margin
of the Tibetan Plateau

作者

JUN LUO , CUI - PING ZHAO , JIAN LU, LIAN - QING ZHOU , and SI HUA ZHENG

发表刊物

《Pure and Applied Geophysic》

摘要

Crustal earthquake focal mechanisms are investigated in the southeastern margin of the Tibetan Plateau, where the Tibetan Plateau and stable South China Block merge. An updated database of focal mechanisms has been compiled by selecting 132 Global Centroid Moment Tensor solutions and by adding the 173 new solutions (3.5 B Ms B 7.4) estimated by waveform inversion in this study. A total of 305 mechanisms are included in this database. These solutions show regionally specific distributions with dominant strike-slip faulting and some normal and reverse faulting. Focal mechanism solutions have also been inverted for the stress tensor orientation to obtain the principal stress axes over the study region. Results show that the horizontal maximum principalr 1 axes rotate clockwise with a wider range than the geodetically measured surface motion in the east, which is not limited to the Xianshuihe–Xiaojiang fault, but has some overlap with the Zhao-tong–Lianfeng fault. Localized normal faulting stress regimes are observed in the Jinshajiang–Litang fault areas and the Baoshan sub-block. The minimum principal axes are oriented with a gradually changing trend from north–south to northwest–southeast, from north to south, indicating diverse compression stress patterns. Significant changes in the crustal stress field after the Wenchuan earthquake are preliminarily observed in the Baoshan sub-block where orientations of two principal axes have changed, and in the
Jinggu–Ximeng sub-block areas where the strike-slip faulting stress pattern has transformed to normal faulting.

题目

中国东北地区北部上地幔各向异性及其动力学意义

作者

强正阳，吴庆举

发表刊物

《地球物理学报》

摘要

中国东北地区广泛发育新生代板内火山，晚中生代以来岩石圈遭受过多期拉张作用．作为中国唯一的深震孕育区，中国东北地区受到太平洋板块的西向俯冲，使得其成为研究岩石圈变形、板块俯冲和板内火山成因及其相互作用关系的天然实验室．通过分析架设在中国东北地区北部的１４７个流动和固定台站的 SＫＳ波形数据，共计得到了３７７对各向异性参数和２５１个无效分裂结果．结果表明，中国东北地区东西两侧具有不同的各向异性分布：西部地区各向异性方向变化范围为Ｎ１４３—１９９°Ｅ，平均Ｎ１６９°Ｅ，与晚中生代岩石圈伸展方向一致；其各向异性延迟时间平均值约为０．８ｓ，说明来自地幔的各向异性比较微弱，主要由残留在岩石圈中的古老变形所引起．同时，在松辽盆地和佳木斯地块部分区域，观测到延迟时间较小的各向异性（～０．４ｓ），可能是由于岩石圈的拆沉和热地幔物质的上涌侵蚀了保留在岩石圈的古老形变所致．在研究区东部，ＮＮＷ-ＳＳＥ朝向的各向异性被观测到，并伴随较大的延迟时间（大于１．０ｓ），可能与太平洋板块撕裂回撤而产生的地幔流动有关．此外，近ＷＥ方向的各向异性只在佳木斯地块被观测到，而太平洋板块在地幔过渡带中的俯冲可能是其产生的主要成因．

我所2016年发表论文欣赏-第十六期

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