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Some geomorphic indices in the North Central Vietnam
Geosciences Journal ( IF 1.0 ) Pub Date : 2021-04-28 , DOI: 10.1007/s12303-021-0006-6
Nguyen Anh Duong , Vu Van Chinh

We have applied geomorphology to investigate the tectonic fault in the North Central Vietnam. At the local scale, the active tectonic possibility of fault zones in the study area is geomorphologically assessed for the first time. The results show the geomorphic indices of drainage basin asymmetry (AF = 0–34), valley floor width-to-height ratio (Vf = 0.21–1.71) applied to 50 drainage basins and mountain-front sinuosity (Smf = 1.07–1.58) calculated along 17 tectonic fault zones. The geomorphic analysis indicates that the modern activity of faults in the study area is moderate-weak. Only a few segments of the Truong Son and Dakrong-Hue faults are assessed as strongly active. The tectonic activity of this area is assessed with an average uplifting rate of about 0.2 mm/year according to the Smf and Vf analyses. In order to prove the existence of faults as well as their active possibility, the field survey has also been carried out by structural geological and geomorphological methods. The survey was conducted at 369 outcrops and approximately 12,000 fractures were measured. Based on the data on displacement and the processing of data on slip observed at the outcrops, we have identified the strike-slip tectonic stress state of Pliocene-Quaternary period with the sub-longitudinal compressional direction and the slip mechanism of fault zones in this period. It is a new finding of the contemporary crustal stress orientation of North Central Vietnam. The results of this study provided the geomorphic evidence to evaluate the potential seismic hazards of the North Central Vietnam.



中文翻译:

越南中北部的一些地貌指数

我们已将地貌学应用于调查越南中北部的构造断裂。在地方尺度上,首次对研究区域断层带的活动构造可能性进行了地貌学评估。结果表明,流域不对称性的地貌指数(AF = 0–34),谷底宽高比(V f = 0.21–1.71)适用于50个流域和山前弯曲度(S mf)= 1.07–1.58)沿17个构造断裂带计算。地貌分析表明,研究区的现代断层活动为中等弱。Truong Son和Dakrong-Hue断层中只有少数断层被认为是强活动的。根据S mf和V f,对该地区的构造活动进行了评估,平均抬升速率约为0.2 mm /年分析。为了证明断层的存在及其活跃的可能性,还通过构造地质和地貌方法进行了野外调查。该调查在369个露头处进行,测量了大约12,000处骨折。根据露头位移数据和露头数据处理,我们确定了上新世-第四纪的走滑构造应力状态,其纵向为亚纵向压缩方向,且断层带的滑移机制在这一时期。这是越南中北部当代地壳应力取向的新发现。这项研究的结果为评估越南北部中部的潜在地震危险提供了地貌证据。

更新日期:2021-04-29
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