Responses of Stream Geomorphic Indices to Piedmont Fault Activity in the Daqingshan Area of China
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Responses of Stream Geomorphic Indices to Piedmont Fault Activity in the Daqingshan Area of China Junyi Wang , Zhongtai He * Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China Junyi Wang: https://orcid.org/0000-0003-0401-4269; Zhongtai He: https://orcid.org/0000-0001-5436-5759 ABSTRACT: A recent correlation of stream geomorphic indices to fault activity has revealed that stream geomorphologies in bedrock mountain areas are good records of local fault movements. The Daqingshan piedmont fault is one of the main active faults in the fault system on the northern margin of the Hetao Basin and has produced frequent large-scale earthquakes since the Late Pleistocene. In the present study, following the segmentation regime of previous studies, we divide the fault zone into five segments, namely, the Baotou, Tuyouqi West, Tuzuoqi West, Bikeqi, and Hohhot segments, and we discuss the relationship between the drainage basin geomorphology and the piedmont fault activity in the Daqingshan area using 30 m spatial resolution Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) data. We use a range of geomorphic indices to examine the drainage basins in the Daqingshan area, including the channel steepness index (ksn), slope, hypsometric integral (HI), relief degree of land surface (RDLS), and stream lengthgradient index (SL), extracted with ArcGIS and MATLAB, and we also consider local lithologic and climate aspects. Furthermore, we compare the geomorphic indices with the slip rates of individual segments of the Daqingshan piedmont fault and paleoseismic data. The results show that the geomorphic indices of drainage basins in the Daqingshan area are primarily affected by the piedmont fault activity in the Daqingshan area. The geomorphic indices also demonstrate that piedmont fault activity has been the most intense in the middle segment of this fault system since the Late Quaternary and decreases towards the two sides. KEY WORDS: Daqingshan piedmont, stream geomorphic index, fault activity, slip rate, paleoearthquake. 0
INTRODUCTION The Daqingshan piedmont fault spreads along the southern piedmont of the Daqingshan mountains, and it starts in the west from the Zhaojun Tomb in Baotou and extends eastward along the Daqingshan piedmont to the Kuisu area east of Hohhot. This region is an important industrial and economic zone in Inner Mongolia, and this fault is one of the main active faults in the fault system on the northern margin of the Hetao fault-depression zone (He and Ma, 2015; He et al., 2007; Ran et al., 2003; Ma et al., 2000; Research Group of Active Fault System around Ordos Massif, 1988). Extensive research since the 1980s has yielded a substantial understanding of the segmentation, active patterns, geomorphology, and strong quake recurrence of this fault (Wang et al., 2018). More recently, with the emergence of high-resolution satellite remote sensing imaging and geographical information system (GIS) technologies, determining fault activity by extracting
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