Morphotectonic properties of the Lo River Fault near Tam Dao in North Vietnam

Abstract. The Lo River fault near Tam Dao, North Vietnam, is a young, right-lateral, normal fault which has been active throughout the Quaternary. Rates of dextral slip range between 1 and 2 mm/yr whereas rates of uplift can be estimated roughly at 0.1–1 mm/yr. The drainage deflection and arrangement of shutter ridges suggest 1.5–2.0 km of dextral offset during the past 1–2 millions of years (m. y.), and the height of the youngest faceted spurs averages at 170 m. Analysis of morphometric parametres of the mountain front at Tam Dao indicates that this segment shows properties typical for nearly rectilinear, young normal scarps that belong to class I or II of relative tectonic activity and that are capable of generating strong earthquakes in the future.

Download Full-text

Pliocene to Quaternary tectonics in the Horná Nitra Depression (Western Carpathians)

Geologica Carpathica ◽

10.2478/v10096-011-0028-5 ◽

2011 ◽

Vol 62 (4) ◽

pp. 381-393 ◽

Cited By ~ 13

Author(s):

Rastislav Vojtko ◽

Juraj Beták ◽

Jozef Hók ◽

František Marko ◽

Vojtech Gajdoš ◽

...

Keyword(s):

Active Fault ◽

Slip Rate ◽

Normal Fault ◽

Western Carpathians ◽

Early Pleistocene ◽

Tectonic Activity ◽

Slip Rates ◽

Compressional Stress ◽

Mountain Front ◽

Half Graben

Pliocene to Quaternary tectonics in the Horná Nitra Depression (Western Carpathians)The Horná Nitra Depression is an Upper Miocene-Quaternary intramontane sedimentary basin. This N-S elongated half-graben structure is rimmed from the west by the marginal Malá Magura fault which is the most distinctive fault in the Horná Nitra Depression, traditionally considered as an active fault during the neotectonic phase. This dislocation is attended by contrasting landforms and their parameters. The lowS-indexof about 1.10, at least two generations of well-preserved faceted slopes along this fault, and longitudinal river valley profiles point to the presence of a low-destructed actual mountain front line, which is typical for the Quaternary active fault systems. Comparison with known normal fault slip rates in the world makes it possible to set an approximate vertical slip rate between 0.3-1.1 m · kyr-1. The present-day fault activity is considered to be normal, steeply dipping towards the east according to structural and geophysical data. The NNW-SSE present-day tectonic maximum horizontal compressional stressSHand perpendicular minimum horizontal compressional stressShwas estimated in the Horná Nitra region. The Quaternary activity of the Malá Magura fault is characterized by irregular movement. Two stages of important tectonic activity along the fault were distinguished. The first stage was dated to the Early Pleistocene. The second stage of tectonic activity can by dated to the Late Pleistocene and Holocene. The Malá Magura fault is permeable for gases because the soil atmosphere above the ca. 150 meters wide fault zone contains increased contents of methane and radon.

Download Full-text