Geomorphic Indices Research Articles

Preliminary assessments of debris flow hazard in relation to geological environment changes in mountainous regions, North Vietnam

Debris flow, widely viewed by geo-scientists as a special combination of landslide and flash flood, causes devastating damages to people and environment in northern mountainous regions of Vietnam. Field observations in the areas damaged by debris flows in northern Vietnam identified types of soils and rocks that were more likely to cause debris flows. Unlike flash floods, almost debris flows occurred at the end of the rainy season when soils and rocks were water-oversaturated thus mechanically weak; this is when pore water pressure decreases, lowering the strength from the soil. Landslides causing debris flows are commonly current slides. The tip of a landslide is often confined within a stream that has a permanent or seasonal flow. Debris flows mainly occur in proluvium, colluvial deposits or tectonic breccia zones. However, not a debris flow initiated in a tectonic breccia zone has been recorded in the northern mountainous regions of Vietnam. Colluvial deposits have been intensively investigated by many researchers worldwide. These deposits are commonly formed in neo-tectonic active zones, weak bed rocks, particularly old metamorphic rocks such as sericite shale, terrigenous and Cenozoic or late Mesozoic volcanic sedimentary rocks that are distributed at steep slopes and/or highly differentiated reliefs. These features appear to be a prerequisite for the exogenous processes, including rolling stones, falling rocks, landslides and surface erosions to occur. To study the mechanical and physical properties of colluvial deposits, the most practical approach is conducting experiments with large-sized samples or on-site experiments. However, this approach is expensive and not always favorable. Applying the rock mechanical theory, it is possible to examine C, j values if values of geological characteristics of rock blocks are known. Thus, the present study attempts clarify the cause-feedback relationship between the change of geological environment and geological hazard in general, and debris flows, in particular, providing a basic scientific insight for studying and predicting debris flows.ReferencesBauziene L., 2000. Colluvisols as a component of erosional and accumulative soil cover structures of east lithuania. European soil Bureau - research report (7), 147-151.Hoek E., Marinos P., 2007. A brief history of the development of the Hoek-Brown failure criterion, Soils and Rocks, 2, 1-8.Irfan T.Y., Tang K.Y., 1992. Effect of the coarse fractions on the shear strength of colluvium. Geo report No 23, Geotechnical Engineering office, Civil Engineering Department Hong Kong.Lai K. W., 2011. Geotechnical properties of colluvial and alluvial deposits in Hong Kong. The 5th cross-strait Conf on Structural and geotechnical engineering (SGE-5), 735-744, Hong Kong China, 13-15 July 2011.Ngo Van Liem, Phan Trong Trinh, Hoang Quang Vinh, Nguyen Van Huong, Nguyen Cong Quan, Tran Van Phong, Nguyen Phuc Dat, 2016. Analyze the correlation between the geomorphic indices and recent tectonics of the Lo River fault zone in southwest of Tam Dao range, Vietnam J. Earth Sci., 38(1), 1-13.Richard E. Gray, 2008. Landslide problems on appalachian colluvial slopes. Geohazards in transportation in the appalachian region, Charleston, WV.Robert W. Fleming, Johnson M. Arvid, 1994. Landslide in Colluvium. U.S. Geological Survey Bulletin 2059-B.Tran Trong Hue (edit), 2004. Integrated assessment of geological disasters in Vietnam territory and prevention solutions (Phase II: The northern mountainous provinces), Report on Phase II of the Independent National project. Institute of Geology, Hanoi, 2003.Tran Van Tu (edit), 1999. Study of the scientific basis of formation and development of mountain floods (including flash floods), proposing the solution of warning, mitigation, and reduction of natural disasters and damage. Report of the project of the Vietnam Centre for Science and Technology, 1998 - 1999.Tran Van Tu, 2012. Scientific basis and method to set up the map of zonation area for sweeping flood, Journal of Sciences of the Earth, 34(3), 7-13.

A wavelet perspective on variabilities of hydrological processes in conjunction with geomorphic analysis over the Pearl River basin in South China

Basin response to precipitation variability by terrestrial hydrological processes may be manifested at different timescales and vary from one basin to another. A quantitative grasp of natural variability modulation is desirable for characterizing basin tendency or vulnerability on floods and droughts; quantification is not always straightforward, however. Using a macro-scale hydrological model, the Variable Infiltration Capacity (VIC) model, the hydrological time series (runoff, soil moisture, and evapotranspiration) were obtained for the 10 sub-basins over the Pearl River basin in South China for the period 1952–2000. A continuous wavelet transform was used to identify the characteristics of the temporal scales of basin-featured extreme events and related multiple-scale variabilities. By use of wavelet coherence analysis and rank correlation method, the cross correlations of monthly anomalies of hydrological processes were examined. The results showed that the runoff correlated most with, and the evapotranspiration had less response to, the precipitation variability. The analyzed results revealed that the attenuation effect of runoff in response to precipitation variability was mainly within the timescale of 2 yr in the Pearl River basin. The soil moisture variability can extend precipitation variation along with timescales. With understanding of the variability features of the terrestrial hydrological processes, this paper showed one geomorphic index, a basin form factor (FF), can represent the wavelet-based indices for high- and low-frequency responses to precipitation variability. It was found that, for a sub-basin with a higher FF value, precipitation variability can be represented more by runoff variability at less than 2-yr timescales; such a sub-basin is apt to have serious floods. With a lower FF value, a sub-basin has longer memory of soil moisture, leading to severe droughts during dry periods. This finding would be valuable to evaluate the tendency on occurrence of floods and droughts in the Pearl River basin, a humid region, which may be transferable to other basins in the globe.

Tectonic variability along the South Katrol Hill Fault, Kachchh, Western India: Insights from geomorphic indices

Tectonic variability along the South Katrol Hill Fault, Kachchh, Western India: Insights from geomorphic indices

Geomorphic indices and relative tectonic uplift in the Guerrero sector of the Mexican forearc

Tectonically active areas, such as forearc regions, commonly show contrasting relief, differential tectonic uplift, variations in erosion rates, in river incision, and in channel gradient produced by ongoing tectonic deformation. Thus, information on the tectonic activity of a defined area could be derived via landscape analysis. This study uses topography and geomorphic indices to extract signals of ongoing tectonic deformation along the Mexican subduction forearc within the Guerrero sector. For this purpose, we use field data, topographical data, knickpoints, the ratio of volume to area (RVA), the stream-length gradient index (SL), and the normalized channel steepness index (ksn).The results of the applied landscape analysis reveal considerable variations in relief, topography and geomorphic indices values along the Guerrero sector of the Mexican subduction zone. We argue that the reported differences are indicative of tectonic deformation and of variations in relative tectonic uplift along the studied forearc. A significant drop from central and eastern parts of the study area towards the west in values of RVA (from ∼500 to ∼300), SL (from ∼500 to ca. 400), maximum SL (from ∼1500–2500 to ∼1000) and ksn (from ∼150 to ∼100) denotes a decrease in relative tectonic uplift in the same direction. We suggest that applied geomorphic indices values and forearc topography are independent of climate and lithology. Actual mechanisms responsible for the observed variations and inferred changes in relative forearc tectonic uplift call for further studies that explain the physical processes that control the forearc along strike uplift variations and that determine the rates of uplift. The proposed methodology and results obtained through this study could prove useful to scientists who study the geomorphology of forearc regions and active subduction zones.

Spatial and temporal variations in denudation rates derived from cosmogenic nuclides in four European fluvial terrace sequences

The denudation of landscapes is affected by temporal and spatial variations in tectonics, climate, and vegetation. However, deciphering the contributions of these different processes has proven challenging. In this study, cosmogenic nuclide-derived modern and paleo catchment-wide denudation rates in four European rivers are investigated. We present 12 new and 4 recalculated cosmogenic nuclide-derived denudation rates from modern river sediments and 14 paleo-denudation rates from terraces deposited over the last 2 Ma. The catchments studied are located in regions with minimal Quaternary tectonic activity and span different climates over 12o latitude. Results indicate that modern denudation rates range between 16 ±11 and 51 ±7 mm/ka with no clear latitudinal variation. Modern denudation rates are compared with catchment geomorphic indices including slope, fluvial steepness index, and relief. The denudation rates correlate better to catchment topographic indices (R2 ≈ 0.4) rather than climate. Paleo-denudation rates range from 8 ±7 to 56 ±7 mm/ka and are associated with a possible increase in the average paleo-denudation rates over the past 2 Ma. Taken together, the results indicate that quantification of catchment-wide denudation rates over long (Quaternary) time scales because of climate change is difficult. Future work to study climate influence on denudation rates should focus on the successes of previous work that document transient denudation rates over shorter and more recent time scales, i.e., from the Last Glacial Maximum to present.

Active tectonics evaluation from geomorphic indices for the central and the southern Longmenshan range on the Eastern Tibetan Plateau, China

We applied the geomorphic indices (hypsometry and stream length gradient) to evaluate the differential uplift of the central and southern Longmenshan, a mountain range characterized by rapid erosion, strong tectonic uplift and devastating seismic hazards. The results of the geomorphic analysis indicate that the Beichuan-Yingxiu fault and the Shuangshi-Dachuan fault act as major tectonic boundaries separating areas experiencing rapid uplift from slow uplift. The results of the geomorphic analysis also suggest that the Beichuan-Yingxiu fault is the most active fault with largest relative uplift rates compared to the rest of the faults in the Longmenshan fault system. We compared reflected relative uplift rates based on the hypsometry and stream length gradient indices with geological/geodetic absolute rates. Along-strike and across-strike variations in the hypsometry and stream length gradient correlate with the spatial patterns derived from the Apatite Fission Track (AFT) exhumation rates, the leveling-derived uplift rate, and co-seismic vertical displacements during the 2008 Wenchuan earthquake. These data defined multiple fault relationships in a complex thrust zone and provided geomorphic evidence to evaluate the potential seismic hazards of the southern Longmenshan range.

Remote Sensing Exploration of Nb-Ta-LREE-Enriched Carbonatite (Epembe/Namibia)

On the example of the Epembe carbonatite-hosted Nb-Ta-LREE deposit, we demonstrate the use of hyperspectral reflectance data and geomorphic indicators for improving the accuracy of remote sensing exploration data of structurally-controlled critical raw material deposits. The results further show how exploration can benefit from a combination of expert knowledge and remotely-sensed relief, as well as imaging data. In the first stage, multi-source remote sensing data were used in lithological mapping based on Kohonen Self-Organizing Maps (SOM). We exemplify that morphological indices, such as Topographic Position Index (TPI), and spatial coordinates are crucial parameters to improve the accuracy of carbonate classification as much as 10%. The resulting lithological map shows the spatial distribution of the ridge forming carbonatite dyke, the fenitization zone, syenite plugs and mafic intrusions. In a second step, the internal zones of the carbonatite complex were identified using the Multi-Range Spectral Feature Fitting (MRSFF) algorithm and a specific decision tree. This approach allowed detecting potential enrichment zones characterized by an abundance of fluorapatite and pyroxene, as well as dolomite-carbonatite (beforsite). Cross-validation of the mineral map with field observations and radiometric data confirms the accuracy of the proposed method.

Evidence of active tectonics in Southern Calabria (Italy) by geomorphic analysis: the examples of the Catona and Petrace rivers

This work integrates new detailed geomorphic analyses of the Petrace and Catona fluvial network (southern Calabria) with structural geology data in order to characterize the activity of the fault systems intercepting the fluvial basins and to constrain the seismotectonic setting of the study area. Several strong earthquakes (Maw 6.0–7.1) occurred in the last millennium in the area, which is considered among the most seismically active zones in Italy. However, the lack of instrumental data for strong historical earthquakes and the poor exposure of faulted Quaternary sediments, do not allow the easy identification of active, seismogenic faults. We mapped known faults and new minor structures, transversal and parallel to the master faults, through aerial-photo interpretation and DEM analysis. The transversal structures are minor faults and connecting faults accommodating movement between the master faults that slipped generating strong destructive historical earthquakes. The geomorphological analysis highlights markers of recent tectonic activity associated to the mapped faults. Hierarchical parameters and geomorphic indexes of the Petrace and Catona Rivers show drainage anomalies due to active tectonics and reveal the activity of the faults intercepting them. This work shows that, in southern Calabria, besides the known master faults associated with some catastrophic historical earthquakes, minor faults are active and could be sources of low magnitude seismic release. Finally, the geomorphic and geomorphological analyses allow reconstructing the evolution of the Petrace and Catona rivers and fault activity and dating to Late Pleistocene the present day Messina Strait graben configuration.

GIS-based evaluation of geomorphic response to tectonic activity in Makran Mountain Range, SE of Iran

This paper investigates the impact of active tectonics on the geomorphic processes and landscape evolution of Makran Mountain range at southeastern of Iran using spatial analysis of geomorphic indices. We documented how topography and morphology are influenced by active tectonic deformation. Quantitative analysis of the geomorphological response to active tectonics within the study area have been done using drainage basin asymmetry factor (Af), drainage basin shape index (Bs), drainage density index (Dd), hypsometric integral (Hi), mean axial slope of the channel (MASC), topographic roughness (STD), mountain-front sinuosity (Smf) and valley floor width-valley height ratio (Vf). The obtained results from these indices were combined to yield an index of active tectonics (Iat). The indicative values of this index are consistent with the landforms and geology of the study area. The morphometric data (quantitative analysis of geomorphic indices) provides evidence of relative variation in the tectonic activity of the study area and related landforms. The utilization of geomorphic parameters exhibits decrease in the geomorphic response of the landforms from north to south. Also, the Ghasr-e-Ghand fault, based on the front-based indices has an important role in uplift of the middle part of the study area. Based upon the results of this study we suggest a southward tectonic vergence for the Makran Mountain Range.

Evaluation of geomorphic expressions of bedrock Channels in the Western Ghats of southern Kerala, India, through quantitative analysis

Geomorphic expressions embedded within the bedrock channels, originating from the southernmost part of the Western Ghats, India, are quantitatively characterized through well-defined geomorphic indices using digital elevation models (DEM) and geographical information system (GIS) tools. Drainage basin asymmetry (Af), transverse topographic symmetry factor (T), longitudinal profile, stream length gradient index (SL), hypsometric integral and curve (Ihyp), spatial parameters like drainage density (Dd) and dissection index (DI) are used for extraction of information related to the characteristic pattern and behaviour associated with the Karamana river and its two major tributaries. The independent and cumulative analysis of each geomorphic indices indicates adjustment of Karamana river in response to the tectonic activities. Karamana basin, while showing symmetric character as a single unit, exhibits segments of asymmetric nature associated with the terrain tilting and is evidenced from the variable directional oscillation from E, SSE, S, NW and W. Varying characteristics of the longitudinal profiles and abrupt change in the SL index suggest knick points and uplift of the terrain due to tectonic processes. The influence of tectonic process over the stream characteristics is confirmed by identifying higher levels of SL anomalies in unique lithology. The inferences correlate with the low drainage density and high dissection index zones in the region with varying influence of tectonic processes. Though, the Karamana river basin as a single unit shows old age characteristics in the hypsometric analysis and symmetric nature, the longitudinal profile-assisted SL and SL anomaly indices are found to be capable of revealing evidences of differential effects of tectonic activities over the stream characteristics. The deductions are in agreement with field observations on landforms and channel attributes.

Morphotectonic analysis of the Madhumati watershed, northeast Kashmir Valley

The present study examined the morphotectonic parameters of the Madhumati basin with the emphasis on its implication for tectonic activity. Data for this study were obtained from toposheets in digital format which were subjected to field confirmation. We performed digital elevation model (DEM) analysis, and we extracted several geomorphic indices: mountain front sinuosity, valley floor width to valley height ratio, hypsometric curve and integral, stream length gradient index, transverse topography symmetry, drainage basin asymmetry and basin elongation ratio. These morphometric parameters may indicate tectonic activity with a tilt to the south of the northern margin of the Kashmir Basin (Madhumati Catchment). The results reveal that the basin area was 453.71 km2 and the basin was found to be tectonically active with average S mf value 1.14, stream gradient index (SL) 1026.7, Vf 0.13 and T 0.56. The results of elongation ratio 0.15 reveal that the basin is strongly elongate and active. Also, the calculated result of AF 68.52 % reveals that the basin has shifted up right to the trunk stream facing downstream. The results of hypsometric integral 0.49 and convex-up hypsometric curve reveal that the basin has high elevation relative to mean, narrow and incised valleys and has rugged topography, is in youthful stage and is tectonically active.

Geomorphic analysis in areas of low-rate neotectonic deformation: South Epirus (Greece) as a case study

River morphology and the distribution of river deposits reliably reflect the neotectonic activity of a region in relation to rock resistance and climatic changes. Geomorphic indices have been used to identify landscape evolution and active faults, particularly in areas of high-rate tectonic deformation. In areas of low-rate deformation, the influence of neotectonic activity on landscape evolution is less apparent, although it is important. The aim of this study is to examine the region of south Epirus (Greece), a region where the rates of active tectonic processes are low. Because rock resistance is low and the sediment supply is intense in this region, the fault surfaces are either not well preserved or they are covered. For the purposes of this paper, geomorphic analysis (including the drainage basin asymmetry factor, the basin hypsometric curve and integral, the valley floor width-to-height ratio, longitudinal river profiles, the stream-length gradient index normalized by the graded river gradient, and the mountain front sinuosity index) was used to evaluate neotectonic activity and to identify covered, potentially active faults. In places where fault surfaces could be observed, geological mapping and tectonic analysis were applied to determine the fault characteristics. The first result of this work is that important active or potentially active faults extend for a significant distance into the alluvial plains of south Epirus. In this case study, we considered that geomorphic indices constitute a valuable tool for identifying neotectonic activity in regions of low-rate deformation. Furthermore, geomorphic analysis reveals the location of covered fault structures, contributes to evaluating fault capability, and therefore to estimating seismotectonic hazard.

Publisher’s note

This article presents a rebuttal to the entirely ambiguous and unwanted commentary made by Shah (JAES-D-15-00980) on Dar et al. (2014) . The original article was aimed to evaluate the tectono-geomorphic evolution of the Kashmir Valley using geomorphic indices obtained from satellite images and detailed fieldwork. However, Shah while deviating from the core of the article has attempted to build an inexplicable tale about the structural configuration of the region. The comment is primarily based on the misinterpretation regarding the dip direction of a thrust fault. Pertinently, no major ∼SW dipping frontal fault bounding the Pir Panjal Range near Kashmir Valley is shown in the paper by Dar et al. (2014) . The commentator has just recycled already documented text pertaining to general tectonic character of a few ∼NE dipping thrusts i.e., the Main Frontal thrust (MFT) and Raisi Fault (RF). Moreover, some unknown structure named as Kashmir Basin Fault (KBF) by the commentator has been discussed, which does not even exist in the region. The commentary on the whole actually does not relate with the investigation reported by Dar et al. (2014) , hence merits no consideration for publication.

The karst network system of the Sierra de las Nieves (Málaga, Spain). An example of a high relief Mediterranean karst.

The aim of this work is the stochastic simulation of a network of karst conduits in a high relief karst system. The simulation completes the existing cave mapping provided by speleological exploration and connects the recharge area with the discharge at the karst springs. The Sierra de las Nieves karst system is a high relief Mediterranean karst that has allowed the development of a system of large conduits and caves. The system follows the typical pattern of an alpine karst system with two characteristic zones where the development of the caves is different. The first zone, with a mean altitude of 1750 m a.s.l., the Hoyas del Pilar and Torrecilla, is the area with highest altitude where recharge takes place and where the entrance potholes to the system are located. In this zone the cave system has a development mainly along the vertical (with 1000 m of vertical development along a few hundreds of metres of horizontal development) with large shafts and narrow and steep meanders, until the local base level is reached at 700 m a.s.l. In the second zone, the system has a quasi-horizontal development with 300 m of altitude difference for 7 km in the horizontal until the base level of the system at the Río Grande Spring (450 m a.s.l.). The transition between both zones is dominated by the presence of sumps where the conduits have vertical ondulations. The connectivity between the entrance and the resurgence has been demonstrated, in the past, by tracer tests. The system of super caves has been made possible because of the favourable conjunction of lithological, structural, geomorphological, hydrogeological and climatic factors. Geomorphic indices are introduced to describe the three-dimensional karst networks so the known network can be completed (i.e. simulated), taking into account statistical and probabilistic criteria. The simulated system can be used for the mathematical flow simulation of the karst system.

Active tectonics of the Gharasu river basin in Zagros, Iran, investigated by calculation of geomorphic indices and group decision using analytic hierarchy process (AHP) software

The Gharasu river basin in the High Zagros, Iran, was selected as the study area and 6 geomorphic indices were calculated. Each result was divided in 3 classes. The main folds and faults, especially longitudinal thrusts, have important role in differential uplift in the structural area. In this paper, each of the indices has been considered as a criterion and weight is given to each. Expert choice and AHP software were used to calculate the final weight and the consistency ratio CR, after which the raster was drawn. Seven experts in the field of geo-morphology decided the weighting of each of the indices. These calculations were performed for every 7 th decision. Finally, the 7 rasters obtained were averaged and a final raster was obtained.Most of the areas with high and moderate values are located on a crush zone in the Zagros Formed because of the main faulting mechanism of Zagros region. The results of this paper confirm previous research results in this region.

Spatial variations in tectonic activity along the Kachchh Mainland Fault, Kachchh, western India: implications in seismic hazard assessment

The landscape of Kachchh is a unique example of active intraplate region in the world. Various structural features such as domes, faults, folds and associated intrusive suggest early tertiary tectonic history, while youthful topography like youthful nature of the fault scarps and gorges suggests Quaternary tectonic history. Kachchh Mainland Fault (KMF) is a 170-km-long E–W-oriented south-dipping reverse fault situated in pericratonic Mesozoic rift basin in western India. The KMF is a neotectonically active fault substantiated by distinct tectonic geomorphology and seismotectonic history. As Kachchh region experiences an arid climate, it lacks vegetation and provides favorable conditions for assessing the morphology of mountain fronts and gradient of channels using remote sensing to evaluate the relative tectonic activity. We employed the means of quantitative geomorphic analysis extracted from a DEM to access the spatial variation in tectonic activity. The assessment of geomorphic indicators of active tectonics was carried out using tectono-geomorphic parameters such as stream length-gradient index (SL index), mountain front sinuosity (S mf) and valley floor width–height ratio (V f). These parameters were combined to generate the relative index of active tectonics (RIAT) which was further divided into four classes as per degree of tectonic activity. The RIAT classes show segmented nature of KMF, with four segments having decrease in degree of tectonic activity from east toward west. The central and the eastern segments of KMF fall in class 1 and class 2 of RIAT, indicating a relatively higher degree of recent tectonic activity undergone by them. The results of geomorphic analysis are consistent with the landforms present, geological setup and seismicity in the study area. The study would be helpful in accessing the regional seismic hazard from KMF for the entire western India.

Structural Overview and Morphotectonic Evolution of a Strike-Slip Fault in the Zone of North Almora Thrust, Central Kumaun Himalaya, India

The aim of the present research is to provide the base line details of the NNW-SSE trending Raintoli fault (RF) which is running parallel to the North Almora Thrust (NAT) along the Saryu valley from Seraghat-Naichun to Seri in the central sector of the Uttarakhand Himalaya, India. The RF is characterized as dextral strike slip fault and behaves as a ductile shear zone within the zone of NAT. The dextral sense of shear movement of RF is delineated by the fabric of the shear zone rocks including microscopically observed indicators such as sigma and delta porphyroclasts, quartz c-axis, and the field structural data. Additionally, in the quaternary period the dextral strike slip fault is reactivated with oblique slip component as characterized by various geomorphic indicators, for example, triangular facets, abandoned river channels, unpaired fluvial terraces, and V-shaped valleys with recurrent seismicity. Further, the morphometric parameters including Valley Floor Width to Valley Height (Vf), asymmetry factor (AF), and gradient index (GI) further prove active nature of RF as suggested by low values of hypsometric integration, V-shaped valley, higher gradient index, and tilting of Saryu basin.

Tectonic geomorphology of a large normal fault: Akşehir fault, SW Turkey

In order to better understand the activity of the Akşehir normal fault in SW Turkey and the associated seismic hazard, we investigated the tectonic geomorphology of a 60-km stretch of the 100-km-long Akşehir fault block. The fault can be separated into seven geomorphic segments (1 to 7 from NW to SE) along the mountain front. Segment length varies from about 9 to 14km, and relief of the horst block varies from about 0.6km in the SE to 1.0km in the NW. Analysis of the tectonic geomorphology of 32 drainage basins and mountain front facets using a combination of geomorphic indices reveals a general pattern of high slip rates in the northern and central segments and low slip rates in the southern, probably older, segments. We show that mountain front sinuosity varies from about 1.1 to 1.4 on segments S1-S6 to 2.4 on segment S7, suggesting that the six northern segments are more active than the southernmost segment. Similarly, χ analysis and slope-area analysis of streams reveal a pattern of steepest channels draining the central and northern segments of the horst. The ratio of valley floor width to valley height varies from 0.2 to 0.6, which are typical values for tectonically active mountain fronts; and alluvial fans along segments S1, S2, and S4 are back-tilted. Finally, we show that (1) shapes of the ~100–900m high mountain front facets are mostly triangular (~80%) and partly trapezoidal (~20%); (2) facet slopes range from 6 to 22°; (3) facets at the NW and SE segment ends are larger than the intervening facets; and (4) steepest facets occur along the central segments. Uplift rates estimated from the slope of mountain front facets range from about 0.06m/ky on the southernmost fault segment (S7) to 0.23m/ky on the more central S5 and 0.16m/ky on the northern segment (S1). The estimated pattern of uplift is consistent with the pattern of geomorphic indices. The vertical relief of the facets suggests that uplift of the mountain front initiated in the late Miocene-early Pliocene and continues to the present, with the earliest surface-rupturing faults on the southernmost fault segment (S7).Large normal faults with a similar slip rate of 0.2–0.3m/ky typically have strong earthquakes every few thousand years. Therefore, the many moderate to strong earthquakes on the Akşehir fault in the past few hundred years may be misleading. A paleoseismic evaluation could answer questions concerning the area's earthquake hazard. The tectonic geomorphology suggests that the Akşehir fault is active, and larger earthquakes than those of the historic period are a potential threat.

Relative tectonics and debris flow hazards in the Beijing mountain area from DEM-derived geomorphic indices and drainage analysis

The geomorphic setting of the tectonically active area around Beijing is a result of complex interactions involving Yanshan neotectonic movements and processes of erosion and deposition. The Beijing Mountain study area contains the junction of two mountain ranges (the Yanshan Mountains and the Taihang Mountains). Tectonic activity has significantly influenced the drainage system and the geomorphic situation in the area, leading to a high probability of the development of debris flows, which is one of the major abrupt geological disasters in the region. Based on 30-m-resolution ASTER GDEM data, a total of 752 drainage basins were extracted using ArcGIS software. A total of 705 debris flow valleys were visually interpreted from ALOS satellite images and published documents. Seven geomorphic indices were calculated for each basin including the relief amplitude, the hypsometric integral, the stream length gradient, the basin shape indices, the fractal dimension, the asymmetry factor, and the ratio of the valley floor width to the height. These geomorphic indices were divided into five classes and the ratio of the number of the debris flow valleys to the number of the drainage basins for each geomorphic index was computed and analyzed for every class. Average class values of the seven indices were used to derive an index of relative active tectonics (IRAT). The ratio of the number of the debris flow valleys to the number of the drainage basins was computed for every class of IRAT. The degree of probable risk level was then defined from the IRAT classes. Finally, the debris flow hazard was evaluated for each drainage basin based on the combined effect of probable risk level and occurrence frequency of the debris flows. The result showed a good correspondence between IRAT classes and the ratio of the number of the debris flow valleys to the number of the drainage basins. Approximately 65% of the drainage basins with occurred debris flow valleys are at a high risk level, while 43% of the drainage basins without occurred debris flow valleys are at a high risk level. A comparison with results from past studies demonstrated that the accuracy of these findings is greater than 85%, indicating that the basin topography created by rapid tectonic deformations is more favorable for debris flows.

Relative tectonic activity assessment of the Çameli Basin, Western Anatolia, using geomorphic indices

Western Anatolia is one of the world’s most seismically active regions. A nearly N–S-oriented extension caused the formation of E–W- and NE–SW-trending major grabens, creating the potential for earthquakes with magnitudes ≥ 5. The fault segments of the NE-trending Çameli Basin were evaluated using geomorphic indices, common tools for assessment of relative tectonic activity in such areas. Quantitative measurement of geomorphic indices including mountain-front sinuosity (Smf; 1.35–2.39), valley floor width-to-height ratios (Vf; 0.08‒0.37), and hypsometric integral (HI; 0.31–1.05) suggest relatively higher tectonic activity along western and southern part of the basin. Hypsometric curves for all segments of the faults mostly exhibit concave or straight profiles, signifying existence of young mountain fronts in the Çameli Basin. These calculations indicate that the Çameli Basin is tectonically active and, southern/south-western areas of this depression have earthquake potential, consistent with epicentres of recent earthquakes, occurred along some fault segments. Possible reason of this activity seems to be related to the E–W-trending corridor lying between the Gulf of Gökova and south-eastern part of the Çameli Basin, represented by active normal faults. These findings should be valid beyond the Çameli Basin for similar situations along the Isparta Angle’s western margin.