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（St）,and the normalized channel steepness index（k_（sn））.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 R_（VA）（from ~500 to^300）,St（from ~500 to ca.400）,maximum St（from ~1500-2500 to ~ 1000） and k_（sn）（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.

Tectonic control on slow-moving Andean landslides in the Colca Valley,Peru

The Colca Valley in the Central Andes is a region characterized by the occurrence of large slow-moving landslides and a high level of seismic activity.In this study,we aimed to determine passive and active tectonic control on the formation of selected five large landslides in the Colca Valley and to assess geohazard associated with these features.For that purpose,we performed a post-landslide field survey,applied remote sensing techniques,and obtained eyewitness accounts.Recently,the need to understand mass movement processes in this region is even higher due to the establishment of the Colca y Volcanes de Andagua Geopark(Colca and Andagua Volcanoes Geopark).Our results suggest that the studied landslides usually represent a complex failure mechanism,dominated by translational sliding or rotational displacements,commonly associated with the formation of horst-and-graben like structures.We found a spatial correlation between the distribution of landslides and inherited fault network.The head scarps appear to be limited by the WNW-to NW-striking faults,whereas the lateral extent of some of the reported features seems to be connected with the NNE-striking normal faults,common in both,the Mesozoic strata and the Pleistocene-Holocene deposits.

Assessment of tectonic control on the development of low mountains moderate relief in the Outer Carpathians(Southern Poland)

Inherited tectonic structures,ongoing tectonic deformation,and variations in relative rock uplift rates play an important role in conditioning the processes of relief development.Their influence among other factors,such as climate and lithology,can be quantified using landscape analysis,and geomorphometric indices,in particular.The usage of landscape analysis in recent years is increasing systematically due to the constant improvement of the digital elevation models and GIS software that significantly facilitate this approach.In this study,we aim to recognize the influence of tectonic structures and processes on relief development in the low mountains with moderate relief of the Sola River catchment in the Western Outer Carpathians.To this end,we calculated geomorphometric indices(river longitudinal profile,stream-length gradient index,minimum bulk erosion,relief ratio,circulatory ratio,elongation ratio,and hypsometric integral)for the Sola River and its 47 sub-catchments using a 25-m spatial resolution Digital Terrain Elevation Data Level 2.Additionally,we identified lineaments and knickpoints and correlated the computed results with local and regional fault networks,variations in lithology,and climate fluctuations.Obtained results indicate a significant impact of inherited tectonicstructures on the relief development of the Sola River catchment,i.e.,directions of principal ridges and valleys follow the orientation of main folds and faults recorded in this area.Anomalously high values of minimum bulk erosion,river gradient,and streamlength gradient index allowed us to define two areas with higher relative uplift rates:1)the So?a Gorge and 2)the Beskid Zywiecki Mts.Polish Outer Carpathians are generally considered as an area of low strain rate and low seismic activity.However,the possibility of neotectonic processes should be considered in geohazard estimations.Observed bends in the direction of river valleys that do not correspond with changes in lithology could be related to active strikeslip faults.These are probably the reactivated basement structures,copied in the thin-skinned nappe cover,as a result of the accommodation of the Mur-Zilina Fault Zone resulting from the tectonic push of the Alcapa(Alpine-Carpathian-Pannonian)microplate against the European plate.Thus,the role of recent tectonic activity in relief development of the Sola River catchment even though appears to be subsidiary at the most,should not be excluded.